A 3-month-old boy is brought to the emergency department after his mother found him to be extremely lethargic. He was born at home with no prenatal care and has no documented medical history. On presentation, he is found to have shorter stature and increased weight compared to normal infants as well as coarse facial features. Physical exam reveals a large protruding tongue and an umbilical hernia. The patient otherwise appears normal. Laboratory tests confirm the diagnosis, and the patient is started on appropriate treatment. The physician counsels the parents that despite initiation of treatment, the boy may have lasting mental retardation. Which of the following is most likely associated with the cause of this patient's disorder?
Q32
A 7-month-old boy is brought to the emergency department by his mother because of a 3-day history of vomiting and poor feeding. The vomit is non-bloody. He transitioned to pureed vegetables 10 days ago. Over the past 2 weeks, he has become increasingly irritable and within the past day has taken more daytime naps and appears much less responsive and interactive. His mother denies any history of fever or trauma at home. He has not received any vaccinations as his parents believe he is already healthy and does not need them. He spends most of the day with a babysitter while both parents are at work. He appears lethargic. His temperature is 37.8°C (100.1°F), pulse is 140/min, respirations are 18/min, and blood pressure is 90/55 mm Hg. The abdomen is soft and nontender. Auscultation of the heart and lungs shows no abnormalities. The anterior fontanelle is tense and bulging. Fundoscopic exam shows bilateral retinal hemorrhage. A complete blood count shows a leukocyte count of 10,000/mm3. An x-ray of the chest shows healing fractures of the 2nd and 3rd right ribs. Further evaluation of this patient is most likely to show which of the following findings?
Q33
A 7-month-old boy presents to the emergency room with three episodes of vomiting and severe abdominal pain that comes and goes for the past two hours. The patient's most recent vomit in the hospital appears bilious, and the patient had one stool that appears bloody and full of mucous. The mother explains that one stool at home appears to be "jelly-like." On physical exam, a palpable mass is felt in the right lower quadrant of the abdomen. What is the next best diagnostic test for this patient?
Q34
A 5-month-old male presents to the pediatrician with his mother for a well visit. The patient was born at 35 weeks gestation to a 30-year-old gravida 2 via vaginal delivery. The pregnancy and labor were uncomplicated. The patient required no resuscitation after delivery and was discharged from the hospital on day two of life. His mother now reports that the patient has been exclusively breastfed since birth, and she says that feedings have been going well, and that the patient appears satisfied afterwards. The patient feeds for 30 minutes every two hours and urinates 8-10 times per day. The patient’s mother reports that she eats a varied diet that includes animal products, but she worries that the patient is not meeting his nutritional needs with breastmilk alone. The patient’s height and weight at birth were in the 15th and 20th percentile, respectively. His height and weight are now in the 20th and 25th percentile, respectively. His temperature is 98.1°F (36.7°C), blood pressure is 58/46 mmHg, pulse is 128/min, and respirations are 34/min. On physical exam, the patient appears well-developed and well-nourished. He has mild conjunctival pallor.
Which of the following is the most appropriate guidance regarding this patient’s nutritional needs?
Q35
A 3-year-old girl is brought to the emergency department because of an inability to walk for a few days. The patient’s mother says that the child was lying on the bed and must have fallen onto the carpeted floor. She lives at home with her mother and her 3-month-old brother. When the patient is directly asked what happened, she looks down at the floor and does not answer. Past medical history is noncontributory. Physical examination shows that the patient seems nervous and has noticeable pain upon palpation of the right thigh. A green-colored bruise is also noted on the child’s left arm. Radiographs of the right lower extremity show a femur fracture. Which of the following is the next best step in management?
Q36
A 9-year-old boy is brought to the physician because of short stature. He has always had short stature around the 35th percentile on the growth curve. Over the past year, he has dropped further on the curve, despite maintaining the same diet. He has a history of low birth weight. The vital signs include: respiration rate 18/min, pulse 85/min, and blood pressure 110/65 mm Hg. His conjunctiva and nail beds are pale. Several hyperpigmented and hypopigmented patches are seen on the back. Chest inspection reveals pectus carinatum and prominent knobs of bone at most costochondral junctions. The thumbs are short, and he has bow legs. There are also petechiae on the lower limbs. The remainder of the physical exam shows no abnormalities. The laboratory results are as follows:
Hemoglobin 8.2 g/dL
Mean corpuscular volume 105 μm3
Platelet count 35,000/mm3
Serum
Na+ 131 mEq/L
K+ 2.8 mEq/L
Cl- 105 mEq/L
Phosphorus (inorganic) 2.5 mg/dL (3.0–4.5 mg/dL)
Arterial blood gas analysis on room air:
pH 7.30
PCO2 33 mm Hg
HCO3− 17 mEq/L
Urine
pH 5.0
Glucose 2+
Ketones Negative
Which of the following is the most likely diagnosis?
Q37
A 3-year-old is brought in to the pediatrician's office for a routine checkup. Her parents report that they noticed some regression in their daughter's behavior. She seemed to be progressing well during the first 18 months of her life. She had started saying words such as 'I', 'you' and 'mama' and she was linking words together. She also learned to follow simple instructions. However, over the past few months, they have noticed that she has been forgetting some of the things that she had previously learned and has had difficulty walking. On examination, the physician observes an apparently healthy girl who refuses to make eye contact and only slowly responds to her name. She is observed to wring her hands repeatedly in her lap. Which of the following genetic patterns of inheritance is responsible for this behavioral regression?
Q38
A 10-year-old boy is brought to the physician by his parents for a follow-up examination. He has had a short stature since birth and underwent diagnostic testing. Genetic analyses showed a gain of function mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. He has met all developmental milestones. He is at the 10th percentile for height and 90th percentile for weight. Which of the following additional findings is most likely on physical examination?
Q39
A 10-year-old boy presents to his pediatrician for a well child appointment. The patient has been doing well in school. He plays on a club basketball team and is also a member of the chess club. He has many friends and is very happy. His parents currently have no concerns for him. His temperature is 99.5°F (37.5°C), blood pressure is 127/68 mmHg, pulse is 85/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you note a tall, muscular young boy. He is in the 99th percentile for weight and height. Cardiopulmonary exam is within normal limits. The patient's abdomen is obese, non-tender, and non-distended. Neurological exam is grossly non-focal. Testicular exam is notable for a right-sided testicular mass. Musculoskeletal exam reveals a normal range of motion and 5/5 strength in his upper and lower extremities. Dermatologic exam reveals acne and facial hair on the patient's face. Which of the following is the most likely underlying diagnosis in this patient?
Q40
A 5-year-old child presents with lower-extremity edema for the past 4 days. Three weeks ago, he experienced several days of cough and fever that was treated with acetaminophen. His medical history is unremarkable; he was born after an uneventful term pregnancy. His vaccinations are up to date. At presentation, his blood pressure is 81/42 mm Hg, and heart rate is 111/min. The child is playful and in no acute distress. Physical examination is remarkable only for ocular 'puffiness' and lower-extremity edema. Chest auscultation is clear, and there are no abnormalities during abdominal inspection. A urinalysis shows the presence of proteinuria, but there is no hematuria. What is the most appropriate treatment for this patient?
Growth/Development US Medical PG Practice Questions and MCQs
Question 31: A 3-month-old boy is brought to the emergency department after his mother found him to be extremely lethargic. He was born at home with no prenatal care and has no documented medical history. On presentation, he is found to have shorter stature and increased weight compared to normal infants as well as coarse facial features. Physical exam reveals a large protruding tongue and an umbilical hernia. The patient otherwise appears normal. Laboratory tests confirm the diagnosis, and the patient is started on appropriate treatment. The physician counsels the parents that despite initiation of treatment, the boy may have lasting mental retardation. Which of the following is most likely associated with the cause of this patient's disorder?
A. Genetic microdeletion
B. Congenital infection
C. Lysosomal defect
D. Chromosomal trisomy
E. Iodine deficiency (Correct Answer)
Explanation: ***Iodine deficiency***
- The patient's presentation with **lethargy**, **shorter stature**, **increased weight**, **coarse facial features**, a **large protruding tongue (macroglossia)**, and an **umbilical hernia** are classic signs of **congenital hypothyroidism**.
- **Iodine deficiency** during pregnancy is an important preventable cause of congenital hypothyroidism, as iodine is essential for thyroid hormone synthesis.
- The lack of **prenatal care** in this case suggests possible maternal iodine deficiency, which would impair fetal thyroid hormone production critical for normal neurological development, explaining the risk of **lasting mental retardation** despite postnatal treatment.
- While **thyroid dysgenesis** (absent or underdeveloped thyroid gland) is the most common cause of congenital hypothyroidism in developed countries, it is not among the answer choices. Of the options provided, iodine deficiency is the only established cause of congenital hypothyroidism.
*Genetic microdeletion*
- While genetic microdeletions can cause developmental disorders (e.g., DiGeorge syndrome with 22q11.2 deletion, Prader-Willi syndrome), they present with specific syndromic features that do not match this presentation.
- Microdeletions are not a recognized cause of primary congenital hypothyroidism.
*Congenital infection*
- Congenital infections (TORCH: Toxoplasmosis, Other, Rubella, CMV, HSV) can lead to developmental problems but typically present with **microcephaly**, **hepatosplenomegaly**, **chorioretinitis**, **intracranial calcifications**, or **rashes**.
- The classic hypothyroid features like **macroglossia** and **umbilical hernia** are not typical of congenital infections.
- Congenital infections do not cause primary thyroid dysfunction.
*Lysosomal defect*
- Lysosomal storage diseases (e.g., Hurler syndrome, Hunter syndrome) can cause coarse facial features and developmental delay, but they present with **progressive** symptoms, **skeletal dysplasias**, **corneal clouding**, **hepatosplenomegaly**, and **cardiac valvular disease**.
- These conditions do not respond to thyroid hormone replacement therapy.
- The clinical picture here is consistent with hypothyroidism, not a lysosomal storage disorder.
*Chromosomal trisomy*
- **Trisomy 21 (Down syndrome)** features hypotonia, characteristic facial features (flat facies, upslanting palpebral fissures, epicanthal folds), single palmar crease, and cardiac defects.
- While children with Down syndrome have **increased risk** of developing hypothyroidism, trisomy 21 itself does not cause congenital hypothyroidism; rather, it's an associated condition.
- The patient's specific features (macroglossia, umbilical hernia, coarse facies) in a 3-month-old with no other syndromic features point to **primary hypothyroidism** rather than a chromosomal disorder.
Question 32: A 7-month-old boy is brought to the emergency department by his mother because of a 3-day history of vomiting and poor feeding. The vomit is non-bloody. He transitioned to pureed vegetables 10 days ago. Over the past 2 weeks, he has become increasingly irritable and within the past day has taken more daytime naps and appears much less responsive and interactive. His mother denies any history of fever or trauma at home. He has not received any vaccinations as his parents believe he is already healthy and does not need them. He spends most of the day with a babysitter while both parents are at work. He appears lethargic. His temperature is 37.8°C (100.1°F), pulse is 140/min, respirations are 18/min, and blood pressure is 90/55 mm Hg. The abdomen is soft and nontender. Auscultation of the heart and lungs shows no abnormalities. The anterior fontanelle is tense and bulging. Fundoscopic exam shows bilateral retinal hemorrhage. A complete blood count shows a leukocyte count of 10,000/mm3. An x-ray of the chest shows healing fractures of the 2nd and 3rd right ribs. Further evaluation of this patient is most likely to show which of the following findings?
A. Vitamin deficiency
B. Type I collagen synthesis defect
C. Diffuse axonal damage (Correct Answer)
D. Bacterial infection
E. Mass in the posterior fossa
Explanation: ***Diffuse axonal damage***
- The combination of **lethargy**, vomiting, **bulging fontanelle**, and **retinal hemorrhages** in an infant, especially with unexplained healing fractures, is highly suggestive of **abusive head trauma (shaken baby syndrome)**.
- Diffuse axonal injury (DAI) is a common and severe consequence of abusive head trauma due to the shearing forces from acceleration-deceleration movements, leading to widespread brain damage.
*Vitamin deficiency*
- While vitamin deficiencies can cause various neurological symptoms, they typically do not present with the acute constellation of **retinal hemorrhages**, **bulging fontanelle**, and **healing fractures** seen in this case.
- The symptoms are more indicative of acute injury rather than chronic nutritional deficit.
*Type I collagen synthesis defect*
- This description is characteristic of **osteogenesis imperfecta**, a genetic disorder causing **brittle bones** and frequent fractures, but it does not account for the **retinal hemorrhages** or the **acute neurological symptoms** like a bulging fontanelle.
- The history of gradual neurological decline (irritability, lethargy) and acute intracranial signs are not typical for a collagen defect.
*Bacterial infection*
- While **bacterial meningitis** can cause fever, lethargy, vomiting, and a **bulging fontanelle**, it typically presents with a higher fever, possible neck stiffness, and often a higher **leukocyte count** with left shift.
- The presence of **retinal hemorrhages** and **healing bone fractures** makes infection a less likely primary explanation for all findings.
*Mass in the posterior fossa*
- A posterior fossa mass could explain the vomiting and bulging fontanelle due to increased intracranial pressure, but it would not typically cause **bilateral retinal hemorrhages** or **healing fractures** in the absence of trauma.
- The rapid onset of severe neurological symptoms along with the other signs points away from a slowly growing mass.
Question 33: A 7-month-old boy presents to the emergency room with three episodes of vomiting and severe abdominal pain that comes and goes for the past two hours. The patient's most recent vomit in the hospital appears bilious, and the patient had one stool that appears bloody and full of mucous. The mother explains that one stool at home appears to be "jelly-like." On physical exam, a palpable mass is felt in the right lower quadrant of the abdomen. What is the next best diagnostic test for this patient?
A. Peripheral blood culture
B. Exploratory laparotomy
C. Kidney, ureter, bladder radiograph
D. Complete blood count with differential
E. Abdominal ultrasound (Correct Answer)
Explanation: ***Abdominal ultrasound***
- An abdominal ultrasound is the **next best diagnostic test** for this patient, as the clinical presentation (sudden onset of severe, intermittent abdominal pain, bilious vomiting, **currant jelly stool**, and a palpable **sausage-shaped mass in the right lower quadrant**) is highly suggestive of **intussusception**.
- Ultrasound is **non-invasive**, provides real-time imaging, and can confirm the diagnosis by visualizing the characteristic **"target sign" or "donut sign"**, indicating one segment of the bowel telescoping into another.
*Peripheral blood culture*
- A peripheral blood culture would be considered if there were strong signs of **sepsis or bacteremia**, such as fever, lethargy, or other systemic inflammatory responses, which are not the primary concern here.
- While infection could cause abdominal pain, the classic signs of intussusception (currant jelly stool, palpable mass) point away from an initial bacterial infection requiring blood cultures.
*Exploratory laparotomy*
- Exploratory laparotomy is a surgical procedure and would be considered an **intervention or treatment**, not the initial diagnostic test, especially when less invasive options are available.
- It is typically reserved for cases where non-invasive diagnostics are inconclusive or when there are signs of **perforation or peritonitis** requiring immediate surgical intervention.
*Kidney, ureter, bladder radiograph*
- A KUB radiograph might show signs of obstruction like dilated bowel loops or absence of gas in the colon, but it is **not definitive for intussusception** and has low sensitivity for diagnosing it.
- It would not provide the detailed soft tissue visualization necessary to confirm the telescoping of the bowel that an ultrasound would.
*Complete blood count with differential*
- A CBC with differential would provide information about the patient's **hemoglobin, white blood cell count**, and platelet count, which can indicate infection or anemia.
- While it may show elevated white blood cells in response to inflammation or ischemia, it is a **non-specific test** and would not definitively diagnose intussusception.
Question 34: A 5-month-old male presents to the pediatrician with his mother for a well visit. The patient was born at 35 weeks gestation to a 30-year-old gravida 2 via vaginal delivery. The pregnancy and labor were uncomplicated. The patient required no resuscitation after delivery and was discharged from the hospital on day two of life. His mother now reports that the patient has been exclusively breastfed since birth, and she says that feedings have been going well, and that the patient appears satisfied afterwards. The patient feeds for 30 minutes every two hours and urinates 8-10 times per day. The patient’s mother reports that she eats a varied diet that includes animal products, but she worries that the patient is not meeting his nutritional needs with breastmilk alone. The patient’s height and weight at birth were in the 15th and 20th percentile, respectively. His height and weight are now in the 20th and 25th percentile, respectively. His temperature is 98.1°F (36.7°C), blood pressure is 58/46 mmHg, pulse is 128/min, and respirations are 34/min. On physical exam, the patient appears well-developed and well-nourished. He has mild conjunctival pallor.
Which of the following is the most appropriate guidance regarding this patient’s nutritional needs?
A. Add cow's milk to his diet
B. Supplement his diet with formula
C. No changes are necessary to his diet
D. Supplement his diet with iron and vitamin D (Correct Answer)
E. Add pureed foods to his diet
Explanation: ***Supplement his diet with iron and vitamin D***
- This 5-month-old infant, exclusively breastfed, requires **iron supplementation** because maternal iron stores are depleted by 4-6 months, and breast milk is a poor source of iron. Additionally, **Vitamin D supplementation** is crucial for all exclusively breastfed infants to prevent rickets.
- The presence of mild **conjunctival pallor** further suggests possible iron deficiency.
*Add cow's milk to his diet*
- **Cow's milk** should not be introduced before 12 months of age as it contains high protein and mineral content that can stress an infant's immature kidneys and can lead to **gastrointestinal bleeding**, insufficient iron absorption, and **iron-deficiency anemia**.
- It also has a low iron content and lacks the essential fatty acids necessary for proper infant development.
*Supplement his diet with formula*
- While formula contains iron and vitamin D, the mother reports that the baby is feeding well and appears satisfied, with appropriate weight gain (20th to 25th percentile) and frequent wet diapers, indicating **adequate nutrition from breast milk alone**.
- **Exclusive breastfeeding** is recommended for the first 6 months of life when feasible, and there is no clear indication that breast milk alone is insufficient for overall caloric and macronutrient needs here yet.
*No changes are necessary to his diet*
- This is incorrect because, despite adequate breastfeeding, **exclusive breastfed infants** like this one require supplementation with **iron and vitamin D** to meet their micronutrient needs.
- The mild conjunctival pallor also suggests a potential, or impending, deficiency that warrants intervention.
*Add pureed foods to his diet*
- The current recommendations suggest introducing solid foods, including pureed foods, around **6 months of age**, when the infant shows signs of developmental readiness.
- While the infant is close to 6 months, introducing solids at 5 months is typically not necessary if growth is appropriate and specific micronutrient deficiencies (like iron and vitamin D) can be addressed through supplementation.
Question 35: A 3-year-old girl is brought to the emergency department because of an inability to walk for a few days. The patient’s mother says that the child was lying on the bed and must have fallen onto the carpeted floor. She lives at home with her mother and her 3-month-old brother. When the patient is directly asked what happened, she looks down at the floor and does not answer. Past medical history is noncontributory. Physical examination shows that the patient seems nervous and has noticeable pain upon palpation of the right thigh. A green-colored bruise is also noted on the child’s left arm. Radiographs of the right lower extremity show a femur fracture. Which of the following is the next best step in management?
A. Check copper levels.
B. Run a serum venereal disease research laboratory (VDRL) test.
C. Collagen biochemical testing
D. Obtain a complete skeletal survey to detect other bony injuries and report child abuse case. (Correct Answer)
E. Check vitamin D levels.
Explanation: ***Obtain a complete skeletal survey to detect other bony injuries and report child abuse case.***
- This patient's presentation with a **femur fracture** from a seemingly minor fall onto a carpeted floor, combined with observable **bruising in different stages of healing** (green = older) and the child's **withdrawn behavior**, strongly suggests **non-accidental trauma (child abuse)**.
- A **skeletal survey** is crucial to identify other occult fractures or signs of previous abuse in children under 5 years with suspected abuse.
- **Mandatory reporting** to child protective services is legally required when child abuse is suspected.
- Classic red flags include: **inconsistent mechanism of injury**, femur fractures in non-ambulatory/young children, **bruises of different ages**, and **behavioral changes**.
*Check copper levels.*
- **Menkes disease** (copper deficiency) can cause bone fragility, metaphyseal spurring, and pathologic fractures, but this is a **rare X-linked genetic disorder** that typically presents in infancy with neurologic deterioration and characteristic "kinky hair."
- Does not explain the **bruising pattern** and **behavioral findings** suggestive of abuse.
- This would be a consideration only after ruling out abuse.
*Run a serum venereal disease research laboratory (VDRL) test.*
- **Congenital syphilis** can manifest as **osteochondritis** and **periostitis** (particularly affecting long bones), but typically presents in early infancy with other features like hepatosplenomegaly, rash, snuffles, and saddle nose deformity.
- An isolated femur fracture with bruising in a 3-year-old without other stigmata of syphilis makes this diagnosis unlikely.
- There are no other features to suggest syphilitic infection in this patient.
*Collagen biochemical testing*
- **Osteogenesis imperfecta** causes **brittle bones** due to type I collagen defects, leading to **recurrent fractures** with minimal trauma.
- However, this condition typically presents with a **family history**, **blue sclerae**, **early hearing loss**, and **dentinogenesis imperfecta** in some cases.
- The presence of **bruising of different ages** and the child's **fearful, withdrawn behavior** point more strongly to abuse than a genetic collagen disorder.
- Collagen testing may be considered later if skeletal survey reveals findings consistent with a bone disorder.
*Check vitamin D levels.*
- **Vitamin D deficiency** causes **rickets** in children, characterized by **bowing of legs**, **widening of wrists and ankles**, **rachitic rosary**, and **delayed closure of fontanelles**.
- While rickets can predispose to fractures due to weakened bones, the patient's age, the specific clinical presentation, and particularly the **bruising** and **behavioral findings** make child abuse a far more immediate concern than nutritional deficiency.
- Vitamin D testing could be performed as part of a comprehensive metabolic bone workup if indicated after the abuse evaluation.
Question 36: A 9-year-old boy is brought to the physician because of short stature. He has always had short stature around the 35th percentile on the growth curve. Over the past year, he has dropped further on the curve, despite maintaining the same diet. He has a history of low birth weight. The vital signs include: respiration rate 18/min, pulse 85/min, and blood pressure 110/65 mm Hg. His conjunctiva and nail beds are pale. Several hyperpigmented and hypopigmented patches are seen on the back. Chest inspection reveals pectus carinatum and prominent knobs of bone at most costochondral junctions. The thumbs are short, and he has bow legs. There are also petechiae on the lower limbs. The remainder of the physical exam shows no abnormalities. The laboratory results are as follows:
Hemoglobin 8.2 g/dL
Mean corpuscular volume 105 μm3
Platelet count 35,000/mm3
Serum
Na+ 131 mEq/L
K+ 2.8 mEq/L
Cl- 105 mEq/L
Phosphorus (inorganic) 2.5 mg/dL (3.0–4.5 mg/dL)
Arterial blood gas analysis on room air:
pH 7.30
PCO2 33 mm Hg
HCO3− 17 mEq/L
Urine
pH 5.0
Glucose 2+
Ketones Negative
Which of the following is the most likely diagnosis?
A. Rickets
B. Diamond-Blackfan anemia
C. Renal tubular acidosis type 1
D. Neurofibromatosis type 1
E. Fanconi anemia (Correct Answer)
Explanation: ***Fanconi anemia***
- This condition presents with **short stature**, bone abnormalities (pectus carinatum, prominent costochondral junctions, short thumbs, bow legs), **pancytopenia** (anemia with macrocytosis, thrombocytopenia), and **skin pigmentary changes** (hyperpigmented and hypopigmented patches).
- The abnormal lab findings like **hypokalemia**, **hypophosphatemia**, **metabolic acidosis** with **renal glucose excretion**, and low urine pH can be attributed to **renal tubular dysfunction**, a known feature of Fanconi anemia.
*Rickets*
- While rickets shares some skeletal deformities like **pectus carinatum** and **bow legs**, it primarily involves **vitamin D deficiency** leading to impaired bone mineralization.
- Rickets typically does not explain the **pancytopenia**, **skin pigmentary changes**, or the **renal tubular dysfunction** (hypokalemia, glucose in urine) seen in this patient.
*Diamond-Blackfan anemia*
- This condition is characterized by **pure red cell aplasia**, leading to anemia, but it generally spares other cell lines, unlike the **pancytopenia** observed here (low platelets).
- It does not account for the extensive and diverse range of **skeletal abnormalities**, **skin pigmentary changes**, or **renal tubular dysfunction**.
*Renal tubular acidosis type 1*
- This condition can explain the **metabolic acidosis** (low pH, low HCO3-) and **hypokalemia**, and may contribute to **short stature** due to chronic acidosis.
- However, it does not explain the **pancytopenia** (low hemoglobin and platelets), the **macrocytic anemia**, the **skin pigmentary changes**, or the specific **skeletal abnormalities** like short thumbs and pectus carinatum.
*Neurofibromatosis type 1*
- This genetic disorder is characterized by **café-au-lait spots**, neurofibromas, and often **axillary or inguinal freckling**.
- It does not present with **pancytopenia**, **renal tubular dysfunction**, or the specific congenital **skeletal anomalies** (short thumbs, pectus carinatum) seen in this patient.
Question 37: A 3-year-old is brought in to the pediatrician's office for a routine checkup. Her parents report that they noticed some regression in their daughter's behavior. She seemed to be progressing well during the first 18 months of her life. She had started saying words such as 'I', 'you' and 'mama' and she was linking words together. She also learned to follow simple instructions. However, over the past few months, they have noticed that she has been forgetting some of the things that she had previously learned and has had difficulty walking. On examination, the physician observes an apparently healthy girl who refuses to make eye contact and only slowly responds to her name. She is observed to wring her hands repeatedly in her lap. Which of the following genetic patterns of inheritance is responsible for this behavioral regression?
A. X-linked dominant (Correct Answer)
B. Autosomal dominant
C. Chromosomal trisomy
D. X-linked recessive
E. Autosomal recessive
Explanation: ***X-linked dominant***
- The clinical presentation of a previously thriving girl with **developmental regression**, **loss of acquired skills**, **hand-wringing stereotypies**, and **loss of eye contact** is highly suggestive of **Rett syndrome**.
- Rett syndrome is a classic example of an **X-linked dominant** disorder, primarily affecting girls due to its severe, often lethal, impact in males.
*Autosomal dominant*
- While some neurodevelopmental disorders are autosomal dominant, the specific constellation of symptoms, particularly the **hand-wringing stereotypies** and almost exclusive occurrence in girls with typical male lethality, is not characteristic of typical autosomal dominant inheritance.
- Autosomal dominant disorders affect males and females equally, and severe forms would typically present with a clearer family history or variable expressivity in both sexes.
*Chromosomal trisomy*
- Chromosomal trisomies, such as Trisomy 21 (**Down syndrome**), typically present with congenital anomalies and global developmental delay evident from early infancy, rather than a period of normal development followed by significant regression.
- They also have distinct physical features not described in this case, and while some developmental plateaus can occur, the rapid regression of learned skills and specific motor stereotypies are less characteristic.
*X-linked recessive*
- **X-linked recessive** disorders predominantly affect males (e.g., Duchenne muscular dystrophy, fragile X syndrome), with females usually being carriers and often asymptomatic or having milder symptoms.
- The severe, progressive nature of the neurological regression and the almost exclusive manifestation in girls with Rett syndrome argue against an X-linked recessive inheritance pattern.
*Autosomal recessive*
- **Autosomal recessive** disorders affect males and females equally and often involve metabolic or storage disorders that can cause developmental regression (e.g., Tay-Sachs disease, lysosomal storage disorders).
- However, the specific **hand-wringing movements** and the high prevalence in females with Rett syndrome are not typical features of most autosomal recessive neurodegenerative conditions, which often have different ages of onset and specific neurological findings.
Question 38: A 10-year-old boy is brought to the physician by his parents for a follow-up examination. He has had a short stature since birth and underwent diagnostic testing. Genetic analyses showed a gain of function mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. He has met all developmental milestones. He is at the 10th percentile for height and 90th percentile for weight. Which of the following additional findings is most likely on physical examination?
A. Frontal bossing (Correct Answer)
B. Absent collar bones
C. Long extremities
D. Blue sclerae
E. Small genitalia
Explanation: ***Frontal bossing***
- A gain of function mutation in the **FGFR3 gene** is characteristic of **achondroplasia**, which is a common cause of short stature.
- **Frontal bossing** (prominent forehead) and midface hypoplasia are classical craniofacial features seen in individuals with achondroplasia.
*Absent collar bones*
- **Absent or hypoplastic clavicles** (collar bones) are a hallmark feature of **cleidocranial dysostosis**, a genetic disorder caused by mutations in the *RUNX2* gene, not typically associated with FGFR3 mutations.
- This condition also presents with delayed closure of fontanelles and dental anomalies, which are not suggested by the patient's presentation.
*Long extremities*
- Patients with achondroplasia characteristically have **rhizomelic short stature**, meaning the **proximal limbs** (femur and humerus) are disproportionately shorter than the trunk, leading to short extremities overall, not long ones.
- Long extremities are characteristic of conditions like **Marfan syndrome**, which has distinct genetic and clinical features.
*Blue sclerae*
- **Blue sclerae** are a common finding in **osteogenesis imperfecta**, a genetic disorder characterized by bone fragility due to defects in type I collagen synthesis.
- This condition is not caused by FGFR3 mutations and typically presents with recurrent fractures and other connective tissue abnormalities.
*Small genitalia*
- **Micropenis** (small genitalia) can be associated with various endocrine disorders, such as **hypogonadism** or congenital adrenal hyperplasia, or certain genetic syndromes.
- It is not a characteristic feature of achondroplasia or FGFR3-related skeletal dysplasias.
Question 39: A 10-year-old boy presents to his pediatrician for a well child appointment. The patient has been doing well in school. He plays on a club basketball team and is also a member of the chess club. He has many friends and is very happy. His parents currently have no concerns for him. His temperature is 99.5°F (37.5°C), blood pressure is 127/68 mmHg, pulse is 85/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you note a tall, muscular young boy. He is in the 99th percentile for weight and height. Cardiopulmonary exam is within normal limits. The patient's abdomen is obese, non-tender, and non-distended. Neurological exam is grossly non-focal. Testicular exam is notable for a right-sided testicular mass. Musculoskeletal exam reveals a normal range of motion and 5/5 strength in his upper and lower extremities. Dermatologic exam reveals acne and facial hair on the patient's face. Which of the following is the most likely underlying diagnosis in this patient?
A. Leydig cell tumor (Correct Answer)
B. Normal development in the setting of obesity
C. Pituitary adenoma
D. Precocious puberty
E. Sertoli cell tumor
Explanation: ***Leydig cell tumor***
- The presence of a **right-sided testicular mass** along with signs of **precocious puberty** (acne, facial hair, tall/muscular build) in a 10-year-old boy is highly suggestive of a **Leydig cell tumor**.
- These tumors produce **androgens**, leading to premature secondary sexual characteristics and an accelerated growth spurt.
*Normal development in the setting of obesity*
- While obesity can sometimes be associated with earlier puberty in girls, it is less directly linked to the specific combination of **unilateral testicular mass** and precocious pubertal signs in boys.
- The presence of a **testicular mass** makes "normal development" an unlikely explanation.
*Pituitary adenoma*
- A pituitary adenoma could cause **precocious puberty** via increased gonadotropin release, but it would not explain the **unilateral testicular mass**.
- Such an adenoma would typically present with more generalized signs of increased hormone production without a palpable testicular mass.
*Precocious puberty*
- This patient *does* exhibit signs of **precocious puberty**, but it describes the *symptom complex* rather than the specific underlying cause.
- The question asks for the **most likely underlying diagnosis**, and a Leydig cell tumor is a specific cause that fits all presented findings, including the testicular mass.
*Sertoli cell tumor*
- Sertoli cell tumors can occur in children and may present as a **testicular mass**, but they are often associated with **feminizing effects** (e.g., gynecomastia) due to estrogen production, which is not seen here.
- While some can produce androgens, Leydig cell tumors are more classically associated with the robust virilization observed in this case.
Question 40: A 5-year-old child presents with lower-extremity edema for the past 4 days. Three weeks ago, he experienced several days of cough and fever that was treated with acetaminophen. His medical history is unremarkable; he was born after an uneventful term pregnancy. His vaccinations are up to date. At presentation, his blood pressure is 81/42 mm Hg, and heart rate is 111/min. The child is playful and in no acute distress. Physical examination is remarkable only for ocular 'puffiness' and lower-extremity edema. Chest auscultation is clear, and there are no abnormalities during abdominal inspection. A urinalysis shows the presence of proteinuria, but there is no hematuria. What is the most appropriate treatment for this patient?
A. Oral prednisone (Correct Answer)
B. Plasmapheresis
C. Oral azathioprine
D. No treatment is required
E. Intravenous cyclophosphamide
Explanation: ***Oral prednisone***
- This patient's presentation with **edema**, **proteinuria** without hematuria, and a history of a recent **upper respiratory infection** is classic for **minimal change disease (MCD)**. MCD is the most common cause of nephrotic syndrome in children.
- **Corticosteroids**, such as oral prednisone, are the cornerstone of treatment for MCD, leading to remission in over 90% of cases.
*Plasmapheresis*
- **Plasmapheresis** is a blood purification procedure used in conditions like **Goodpasture's syndrome**, **myasthenia gravis**, or severe cases of **glomerulonephritis** not responsive to other therapies.
- It is not indicated as a primary treatment for **minimal change disease** given its high response rate to corticosteroids.
*Oral azathioprine*
- **Azathioprine** is an **immunosuppressant** used in some autoimmune diseases or as a steroid-sparing agent in steroid-dependent or frequently relapsing nephrotic syndrome.
- It is typically not used as first-line therapy for the initial presentation of **minimal change disease**.
*No treatment is required*
- This patient is exhibiting symptoms of **nephrotic syndrome**, including significant edema and proteinuria, which can lead to complications such as **infections**, **thromboembolism**, and **renal failure**.
- Without treatment, the condition will likely worsen and can lead to severe complications; therefore, treatment is most definitely required.
*Intravenous cyclophosphamide*
- **Cyclophosphamide** is a potent **immunosuppressive agent** reserved for patients with **steroid-resistant** or **frequently relapsing minimal change disease**, or other forms of severe glomerulonephritis.
- It is not the initial treatment of choice for **first-presentation minimal change disease** due to its significant side effects.
