A 3-year-old is brought to the pediatrician by his mother. She is concerned that he appears fatigued all the time. She also mentions that he struggles to get out of his seat after eating his meals and that he waddles when he walks now. The child was born at 39 weeks via spontaneous vaginal delivery. He is up to date on all his vaccines and meeting all developmental goals. A maternal uncle had similar symptoms that started in early childhood. He has a heart rate of 90/min, respiratory rate of 22/min, blood pressure of 110/65 mm Hg, and temperature of 37.0°C (98.6°F). The child appears lethargic. He was much more active during his previous well-child visit. Upon examination, the child has thick calves and uses his hands to support himself as he stands up from a sitting position. His reflexes are decreased bilaterally. Lab studies show elevated creatinine phosphokinase (CPK) and lactate dehydrogenase (LDH). Which of the following is the most likely cause of this patient's condition?
Q182
A 2-week-old newborn girl is brought to the physician for a follow-up examination after the initial newborn examination showed asymmetry of the legs. She was born at term to a 26-year-old woman, gravida 3, para 2. Pregnancy was complicated by a breech presentation and treated with an emergency lower-segment transverse cesarean section. The newborn's head circumference is 35 cm (13.7 in). She is at the 60th percentile for length and 75th percentile for weight. Cardiac examination shows no abnormalities. The spine and overlying skin do not indicate significant abnormalities. Abduction of the right hip after cupping the pelvis and flexing the right hip and knee causes a palpable clunk. The feet exhibit no deformities. Ultrasonography of the hip revealed a 50° angle between the lines along the bone acetabulum and the ilium. Which of the following is the most appropriate next step in management?
Q183
A 2-week-old newborn is brought to the physician because of worsening feeding difficulty since birth. Examination shows a grade 2/6 harsh holosystolic murmur, heard most clearly at the left lower sternal border, and a soft mid-diastolic rumble over the cardiac apex. Echocardiography shows shunting of blood through the ventricular septum during systole. The patient undergoes surgery for closure of the defect. Which of the following sets of changes are expected after successful repair of this cardiac defect?
Left atrial pressure | Left ventricular pressure | Right ventricular pressure
Q184
A 4-year-old girl is brought to the physician by her mother for a follow-up examination. She has a history of recurrent asthma attacks. The mother reports that her daughter has also had mild abdominal pain for the past 2 weeks. The patient's current medications include daily inhaled fluticasone and inhaled albuterol as needed. She appears well. Her temperature is 37°C (98.6°F), pulse is 100/min, and blood pressure is 130/85 mm Hg. The lungs are clear to auscultation. Cardiac examination shows no murmurs, rubs, or gallops. Abdominal examination shows a left-sided, nontender, smooth abdominal mass that does not cross the midline. The remainder of the examination shows no abnormalities. A complete blood count and serum concentrations of electrolytes, urea nitrogen, and creatinine are within the reference range. Which of the following is the most likely diagnosis?
Q185
An otherwise healthy 15-year-old boy comes to the physician for a routine health maintenance examination. He feels well and is doing well in school. He has no history of serious illness. Vital signs are within normal limits. The lungs are clear to auscultation. Cardiac auscultation shows no murmur, but a wide-split S2 that does not change with respiration. If left untreated, this patient is at increased risk for which of the following complications?
Q186
A 6-year-old boy presents to his pediatrician’s office for muscle weakness. The patient is accompanied by his mother who states that he has difficulty running and walking up the stairs. The mother has noticed mild weakness when the patient attempts to sit up from a supine position since he was 4-years-old. Medical history is significant for fractures involving the arms and legs secondary to falling. On physical exam, the child does not appear to be in distress and is conversational. He has a waddling gait along with lumbar lordosis and bilateral calf enlargement. The patient uses his hands to push himself into an upright position when arising from the floor. He has absent patellar and ankle-jerk reflexes. Which of the following is the best next step to confirm the diagnosis?
Q187
A 6-year-old boy is brought to the physician because of inability to concentrate and difficulties completing assignments at school. His mother says that he frequently interrupts others during conversations at home and that his teachers often reprimand him for talking excessively in school. He refuses to play with the other children and often has physical altercations with his classmates. He can jump up and down but he cannot hop on one foot. He eats without assistance but has difficulty using silverware. He cannot follow three-step directions. There is no family history of serious illness. Examination shows a small head, wide-spaced eyes, and short palpebral fissures. His upper lip is thin and flat. He has a sunken nasal bridge and a small jaw. There is a 3/6 pansystolic murmur heard along the left lower sternal border. Which of the following is the most likely cause of these findings?
Q188
A 28-year-old pregnant female presents for a prenatal check-up at 20 weeks gestation, which includes routine screening ultrasound. Fetal ultrasound demonstrates bilateral multicystic dysplastic kidneys. Her pregnancy has been complicated by persistent oligohydramnios. The child requires significant pulmonary support upon delivery. Which of the following clinical findings is most likely present in this child as a result of these abnormalities?
Q189
A 9-year-old girl is brought to her pediatrician by her mother for the evaluation of recent-onset seizures. She has had 2 episodes of generalized tonic-clonic seizures in the past 3 days. Each episode lasted for 1–2 minutes and aborted spontaneously. There is no history of fever, headache, altered behavior, diarrhea, vomiting, or previous seizure episodes. Past medical history is unremarkable. Physical examination reveals: blood pressure 102/64 mm Hg, heart rate 89/min, respiratory rate 16/min, and temperature 37.0°C (98.6°F). She looks anxious but oriented to time and space. Multiple flat hyperpigmented spots are present over her body, each more than 5 mm in diameter. Axillary freckling is present. Cranial nerves are intact. Muscle strength is normal in all 4 limbs with a normal sensory examination. Gait is normal. An eye examination is shown in the exhibit. What is the most likely diagnosis?
Q190
A 4-year-old boy is brought to the pediatrician’s office for a flu-like episode. His father tells the physician that his child has fallen ill several times over the past few months. He also has occasional bouts of night sweats and loss of appetite. He has lost 5 lbs (2.3 kg) in the last 6 months. At the pediatrician’s office, his temperature is 38.9°C (102°F), pulse is 105/min and respiration rate is 18/min. On physical examination, the pediatrician observes a flattened facial profile, prominent epicanthal folds, and a single palmar crease. There are petechiae on the arms and legs. Blood count shows pancytopenia. Bone marrow aspiration is diagnostic for ALL (acute lymphoblastic leukemia), but all cells also show a trisomy. Children with similar genetic anomalies are at an increased risk of developing which of the following neurological conditions as they grow older?
Congenital defects US Medical PG Practice Questions and MCQs
Question 181: A 3-year-old is brought to the pediatrician by his mother. She is concerned that he appears fatigued all the time. She also mentions that he struggles to get out of his seat after eating his meals and that he waddles when he walks now. The child was born at 39 weeks via spontaneous vaginal delivery. He is up to date on all his vaccines and meeting all developmental goals. A maternal uncle had similar symptoms that started in early childhood. He has a heart rate of 90/min, respiratory rate of 22/min, blood pressure of 110/65 mm Hg, and temperature of 37.0°C (98.6°F). The child appears lethargic. He was much more active during his previous well-child visit. Upon examination, the child has thick calves and uses his hands to support himself as he stands up from a sitting position. His reflexes are decreased bilaterally. Lab studies show elevated creatinine phosphokinase (CPK) and lactate dehydrogenase (LDH). Which of the following is the most likely cause of this patient's condition?
A. Mutation in WT gene
B. Nonsense mutation in DMD gene (Correct Answer)
C. Missense mutation in DMD gene
D. Nonsense mutation in DMPK gene
E. Missense mutation in β-thalassemia gene
Explanation: ***Nonsense mutation in DMD gene***
- The patient's symptoms, including **fatigue**, difficulty standing (**Gowers sign**), **waddling gait**, **pseudohypertrophy of calves**, and **decreased reflexes**, are classic for **Duchenne muscular dystrophy (DMD)**.
- **Elevated CPK and LDH** are indicative of muscle damage, consistent with DMD. A **nonsense mutation in the DMD gene** leads to a truncated, non-functional **dystrophin protein**, causing this severe, X-linked recessive condition.
*Mutation in WT gene*
- A mutation in the **WT1 gene** is primarily associated with **Wilms tumor**, a kidney cancer, and occasionally with genitourinary abnormalities, but not with generalized muscle weakness and dystrophy.
- This gene is involved in renal and gonadal development, not directly in muscle function.
*Missense mutation in DMD gene*
- While a missense mutation in the DMD gene would affect dystrophin, it typically leads to a less severe phenotype like **Becker muscular dystrophy**, which has a later onset and milder symptoms.
- The severe, early-onset presentation with marked muscle weakness and pseudohypertrophy is more characteristic of the complete absence or severe dysfunction of dystrophin, usually caused by a nonsense or frameshift mutation.
*Nonsense mutation in DMPK gene*
- A nonsense mutation in the **DMPK gene** is associated with **myotonic dystrophy type 1**, which presents with **myotonia** (delayed muscle relaxation), muscle wasting, and often affects multiple systems (e.g., cataracts, cardiac conduction defects).
- The patient's symptoms of progressive muscle weakness and pseudohypertrophy are not typical for myotonic dystrophy type 1.
*Missense mutation in β-thalassemia gene*
- A missense mutation in the **β-thalassemia gene** (HBB gene) leads to **beta-thalassemia**, a **hemoglobinopathy** characterized by **anemia**, **fatigue**, and often **splenomegaly**, but not primary muscular weakness, Gowers sign, or calf pseudohypertrophy.
- The laboratory findings of elevated CPK and LDH point to muscle damage, not hematological issues.
Question 182: A 2-week-old newborn girl is brought to the physician for a follow-up examination after the initial newborn examination showed asymmetry of the legs. She was born at term to a 26-year-old woman, gravida 3, para 2. Pregnancy was complicated by a breech presentation and treated with an emergency lower-segment transverse cesarean section. The newborn's head circumference is 35 cm (13.7 in). She is at the 60th percentile for length and 75th percentile for weight. Cardiac examination shows no abnormalities. The spine and overlying skin do not indicate significant abnormalities. Abduction of the right hip after cupping the pelvis and flexing the right hip and knee causes a palpable clunk. The feet exhibit no deformities. Ultrasonography of the hip revealed a 50° angle between the lines along the bone acetabulum and the ilium. Which of the following is the most appropriate next step in management?
A. Obtain an X-ray of the right hip
B. Treat using a harness (Correct Answer)
C. Immobilize the hips with a spica cast
D. Obtain an MRI of the right hip
E. Reassure the mother and schedule follow-up appointment in 4 weeks
Explanation: ***Treat using a harness***
- The presence of a **palpable clunk** during hip abduction (Ortolani sign) indicates **developmental dysplasia of the hip (DDH)**, specifically a dislocated hip that can be reduced.
- Given the patient's age (2 weeks old) and the ultrasound finding (alpha angle of 50° indicating mild dysplasia), a **Pavlik harness** is the most appropriate initial treatment to maintain the hip in a flexed and abducted position, promoting proper acetabular development.
*Obtain an X-ray of the right hip*
- **X-rays** are not reliable for diagnosing DDH in newborns and infants under 4-6 months because their bones are largely cartilaginous and not yet ossified.
- **Ultrasound** is the imaging modality of choice for infants in this age group, which has already been performed in this case.
*Immobilize the hips with a spica cast*
- A **spica cast** is typically reserved for older infants (usually >6 months) or cases of DDH that have failed Pavlik harness treatment or involve more severe, irreducible dislocations.
- It is an overly aggressive and unnecessary intervention for a 2-week-old with a reducible hip.
*Obtain an MRI of the right hip*
- **MRI** is generally not indicated as a first-line diagnostic or follow-up tool for routine DDH management in newborns due to the need for sedation and higher cost.
- Its use is usually limited to complex cases, pre-operative planning, or when other imaging modalities are inconclusive.
*Reassure the mother and schedule follow-up appointment in 4 weeks*
- The presence of a **positive Ortolani sign** and an abnormal hip ultrasound definitively indicates DDH, requiring immediate intervention.
- Delaying treatment can lead to worsening dysplasia, making non-surgical management less effective and potentially necessitating more invasive procedures.
Question 183: A 2-week-old newborn is brought to the physician because of worsening feeding difficulty since birth. Examination shows a grade 2/6 harsh holosystolic murmur, heard most clearly at the left lower sternal border, and a soft mid-diastolic rumble over the cardiac apex. Echocardiography shows shunting of blood through the ventricular septum during systole. The patient undergoes surgery for closure of the defect. Which of the following sets of changes are expected after successful repair of this cardiac defect?
Left atrial pressure | Left ventricular pressure | Right ventricular pressure
A. ↓ ↑ no change
B. ↑ ↑ ↑
C. ↓ ↑ ↓ (Correct Answer)
D. ↓ ↓ ↓
E. ↑ ↑ ↓
Explanation: ***↓ ↑ ↓***
- With a successful repair of a **ventricular septal defect (VSD)**, the **left-to-right shunting** of blood decreases significantly or resolves. This directly leads to a **reduction in the volume overload** on the left atrium and left ventricle.
- Consequently, the **left atrial pressure will decrease** because less blood is returning from the pulmonary circulation, which was previously overloaded due to the shunt. The **right ventricular pressure will also decrease** as it no longer receives blood shunted from the left ventricle, reducing the pressure burden on the pulmonary circulation. The **left ventricular pressure, however, will increase** due to the increased afterload from the systemic circulation, as blood is no longer shunted to the lower-pressure pulmonary circulation, leading to a greater resistance to ejection.
*↓ ↑ no change*
- While left atrial pressure would decrease and left ventricular pressure would increase, it is unlikely for **right ventricular pressure to remain unchanged** given the significant change in blood flow dynamics.
- The initial **left-to-right shunt** in VSD directly increases pulmonary blood flow, leading to higher pressures in the right ventricle. Repair of the VSD would alleviate this chronic overload, thereby reducing right ventricular pressure.
*↑ ↑ ↑*
- This option suggests an increase in all three pressures, which is inconsistent with the physiological outcome of a successful VSD repair.
- A decrease in left-to-right shunting would lead to a reduction in volume load on the left atrium and right ventricle, thereby **decreasing their pressures**, not increasing them.
*↓ ↓ ↓*
- While left atrial and right ventricular pressures are expected to decrease, the **left ventricular pressure is expected to increase** after VSD repair.
- The closure of the defect eliminates a low-resistance outflow path, forcing the left ventricle to eject blood against the higher systemic vascular resistance, thus increasing its pressure.
*↑ ↑ ↓*
- This option incorrectly predicts an increase in left atrial and left ventricular pressures, and a decrease in right ventricular pressure.
- Post-repair, the **left atrial pressure should decrease** due to reduced pulmonary venous return, and while right ventricular pressure correctly decreases, the overall pattern is inconsistent with the physiological changes.
Question 184: A 4-year-old girl is brought to the physician by her mother for a follow-up examination. She has a history of recurrent asthma attacks. The mother reports that her daughter has also had mild abdominal pain for the past 2 weeks. The patient's current medications include daily inhaled fluticasone and inhaled albuterol as needed. She appears well. Her temperature is 37°C (98.6°F), pulse is 100/min, and blood pressure is 130/85 mm Hg. The lungs are clear to auscultation. Cardiac examination shows no murmurs, rubs, or gallops. Abdominal examination shows a left-sided, nontender, smooth abdominal mass that does not cross the midline. The remainder of the examination shows no abnormalities. A complete blood count and serum concentrations of electrolytes, urea nitrogen, and creatinine are within the reference range. Which of the following is the most likely diagnosis?
A. Polycystic kidney disease
B. Neuroblastoma
C. Wilms' tumor (Correct Answer)
D. Renal cell carcinoma
E. Lymphoma
Explanation: ***Wilms' tumor***
- The presence of a **nontender, smooth abdominal mass** in a 4-year-old child, along with possible abdominal pain, is highly suggestive of a **Wilms' tumor (nephroblastoma)**.
- This tumor is the most common primary renal malignancy in children, typically presenting as an asymptomatic abdominal mass. The elevated blood pressure may be due to **renin secretion** by the tumor.
*Polycystic kidney disease*
- While it can present with enlarged kidneys and abdominal masses, it is usually bilateral and associated with **renal dysfunction** (abnormal BUN and creatinine), which are normal in this patient.
- **Autosomal recessive polycystic kidney disease** can present in childhood but often has more severe systemic manifestations and bilateral large kidneys.
*Neuroblastoma*
- This tumor typically presents as a **hard, irregular mass** that often **crosses the midline** and can be associated with systemic symptoms like fever, weight loss, and bone pain.
- While it originates from neural crest cells and can present in the retroperitoneum, its characteristic features (firm, irregular, crossing midline) differ from the described smooth, left-sided mass.
*Renal cell carcinoma*
- This is primarily a **tumor of adults**, and it is exceedingly rare in young children.
- It usually presents with a triad of **hematuria, flank pain, and palpable mass**, though this full triad is uncommon.
*Lymphoma*
- Abdominal lymphoma often presents with **generalized lymphadenopathy**, constitutional symptoms (fever, weight loss), and a rapidly growing, often ill-defined mass.
- A primary renal lymphoma presenting as a solitary, smooth, nontender mass in a 4-year-old is highly improbable.
Question 185: An otherwise healthy 15-year-old boy comes to the physician for a routine health maintenance examination. He feels well and is doing well in school. He has no history of serious illness. Vital signs are within normal limits. The lungs are clear to auscultation. Cardiac auscultation shows no murmur, but a wide-split S2 that does not change with respiration. If left untreated, this patient is at increased risk for which of the following complications?
A. Paradoxical embolism (Correct Answer)
B. Infective endocarditis
C. Cerebral aneurysm
D. Left ventricular hypertrophy
E. Sudden cardiac death
Explanation: ***Paradoxical embolism***
- The wide, fixed splitting of S2 is highly suggestive of an **atrial septal defect (ASD)**. An ASD allows for the passage of emboli from the venous circulation to the arterial circulation, bypassing the pulmonary filter, leading to **paradoxical embolism** (e.g., stroke).
- In ASD, the continuous shunt of blood from the left atrium to the right atrium leads to increased right ventricular stroke volume, causing prolonged ejection and delayed closure of the pulmonic valve, resulting in a **fixed split S2** that does not vary with respiration.
*Infective endocarditis*
- While certain congenital heart defects increase the risk of infective endocarditis, isolated **atrial septal defect (ASD)** is not typically associated with a significantly elevated risk for infective endocarditis unless there are other associated defects or complications.
- The **low-pressure shunt** through an ASD does not create turbulent flow patterns that commonly predispose to endocardial damage and subsequent infection.
*Cerebral aneurysm*
- There is no direct association between the presence of an **atrial septal defect (ASD)** and an increased risk of developing cerebral aneurysms.
- Cerebral aneurysms are often linked to systemic conditions like **hypertension**, **atherosclerosis**, or specific genetic disorders, none of which are indicated here.
*Left ventricular hypertrophy*
- In an uncomplicated **atrial septal defect (ASD)**, the shunt is from the left atrium to the right atrium, leading to right ventricular volume overload, not left ventricular hypertrophy.
- **Left ventricular hypertrophy** would typically be seen in conditions that increase left ventricular afterload (e.g., aortic stenosis, hypertension) or preload (e.g., mitral regurgitation), which are not suggested by the findings.
*Sudden cardiac death*
- While some congenital heart defects can lead to **sudden cardiac death**, an isolated, uncomplicated **atrial septal defect (ASD)** in an otherwise healthy adolescent usually does not directly predispose to this outcome.
- Sudden cardiac death is more commonly associated with conditions like **hypertrophic cardiomyopathy**, **long QT syndrome**, or severe structural heart disease, which are not indicated by the clinical presentation.
Question 186: A 6-year-old boy presents to his pediatrician’s office for muscle weakness. The patient is accompanied by his mother who states that he has difficulty running and walking up the stairs. The mother has noticed mild weakness when the patient attempts to sit up from a supine position since he was 4-years-old. Medical history is significant for fractures involving the arms and legs secondary to falling. On physical exam, the child does not appear to be in distress and is conversational. He has a waddling gait along with lumbar lordosis and bilateral calf enlargement. The patient uses his hands to push himself into an upright position when arising from the floor. He has absent patellar and ankle-jerk reflexes. Which of the following is the best next step to confirm the diagnosis?
A. Serum creatine kinase level (Correct Answer)
B. Muscle biopsy
C. Electromyogram
D. Electrocardiogram
E. Genetic testing
Explanation: ***Serum creatine kinase level***
- **Serum creatine kinase (CK)** is the best initial test to confirm the diagnosis of **Duchenne muscular dystrophy (DMD)** in a patient with characteristic clinical features.
- CK levels are typically **markedly elevated** (often 10-100 times the upper limit of normal, reaching 10,000-20,000 U/L or higher) due to ongoing muscle fiber degeneration.
- In the context of this classic clinical presentation (Gower's sign, calf pseudohypertrophy, waddling gait, progressive proximal weakness), a significantly elevated CK effectively confirms the diagnosis.
- This test is **non-invasive, readily available, and cost-effective** as the initial confirmatory step.
*Genetic testing*
- **Genetic testing** for DMD gene mutations (deletions, duplications, or point mutations) is the definitive test and is typically performed **after** an elevated CK level confirms muscle disease.
- While genetic testing identifies the specific mutation and is important for prognosis and genetic counseling, it is not the "next step" - CK testing comes first in the diagnostic algorithm.
- Genetic testing is more expensive and time-consuming than CK measurement.
*Muscle biopsy*
- A **muscle biopsy** showing absent or markedly reduced **dystrophin** on immunohistochemistry was historically the gold standard for diagnosis.
- However, with the availability of **genetic testing**, muscle biopsy is now rarely needed and is generally reserved for cases where genetic testing is inconclusive.
- It is invasive and not the preferred initial confirmatory test.
*Electrocardiogram*
- An **ECG** is important for monitoring **cardiac complications** (cardiomyopathy) in patients with established DMD.
- However, it does not diagnose the primary muscle disorder and would be part of ongoing management rather than initial diagnostic confirmation.
*Electromyogram*
- An **EMG** would show **myopathic changes** (short-duration, low-amplitude, polyphasic motor unit action potentials).
- While this confirms a myopathic process, it is not specific for DMD and does not provide definitive diagnosis.
- EMG is rarely needed when the clinical presentation is classic and CK is markedly elevated.
Question 187: A 6-year-old boy is brought to the physician because of inability to concentrate and difficulties completing assignments at school. His mother says that he frequently interrupts others during conversations at home and that his teachers often reprimand him for talking excessively in school. He refuses to play with the other children and often has physical altercations with his classmates. He can jump up and down but he cannot hop on one foot. He eats without assistance but has difficulty using silverware. He cannot follow three-step directions. There is no family history of serious illness. Examination shows a small head, wide-spaced eyes, and short palpebral fissures. His upper lip is thin and flat. He has a sunken nasal bridge and a small jaw. There is a 3/6 pansystolic murmur heard along the left lower sternal border. Which of the following is the most likely cause of these findings?
A. FMR1 gene mutation
B. Deletion of long arm of chromosome 7
C. Prenatal alcohol exposure (Correct Answer)
D. Nondisjunction of chromosome 21
E. Maternal intake of phenytoin
Explanation: ***Prenatal alcohol exposure***
- The combination of **facial dysmorphology** (small head, wide-spaced eyes, short palpebral fissures, thin upper lip, sunken nasal bridge, small jaw), developmental delays (gross and fine motor, speech, inability to follow multi-step directions), and behavioral issues (inability to concentrate, poor social skills, hyperactivity) is highly suggestive of **Fetal Alcohol Spectrum Disorder (FASD)** caused by prenatal alcohol exposure.
- The presence of a **pansystolic murmur** also points to a possible **congenital heart defect**, which is a common finding in FASD, particularly **ventricular septal defects (VSDs)**.
*FMR1 gene mutation*
- This mutation is associated with **Fragile X syndrome**, which presents with intellectual disability, behavioral problems (e.g., hyperactivity, autism-like features), and characteristic physical features.
- While there is some overlap in symptoms, the **facial dysmorphology** described (small head, thin upper lip, sunken nasal bridge) is not typical for Fragile X syndrome, which often involves a long narrow face, prominent ears, and macroorchidism in males.
*Deletion of long arm of chromosome 7*
- This refers to **Williams syndrome**, characterized by an "elfin" facial appearance (small upturned nose, long philtrum, full lips), intellectual disability, and a distinct personality (overly friendly, excitable).
- While it can present with **cardiovascular problems** (classically supravalvular aortic stenosis), the described facial features and behavioral issues do not precisely match Williams syndrome; for example, the patient's aggression and refusal to play with others are not typical.
*Nondisjunction of chromosome 21*
- This causes **Down syndrome**, characterized by intellectual disability, characteristic facial features (upslanting palpebral fissures, epicanthal folds, flat nasal bridge, small ears, single palmar crease), and a high incidence of congenital heart disease (e.g., AVSD).
- The described facial features (small head, wide-spaced eyes, short palpebral fissures, thin upper lip, sunken nasal bridge, small jaw) are inconsistent with the classic presentation of Down syndrome.
*Maternal intake of phenytoin*
- **Fetal hydantoin syndrome** (or fetal phenytoin syndrome) is associated with prenatal phenytoin exposure and can cause growth deficiency, developmental delay, and craniofacial anomalies such as a broad nasal bridge, epicanthal folds, and widely spaced eyes.
- However, the combination of specific facial features (e.g., thin upper lip, sunken nasal bridge, small jaw) and the prominent behavioral and developmental issues, particularly the hyperactivity and severe social difficulties, are more strongly indicative of FASD.
Question 188: A 28-year-old pregnant female presents for a prenatal check-up at 20 weeks gestation, which includes routine screening ultrasound. Fetal ultrasound demonstrates bilateral multicystic dysplastic kidneys. Her pregnancy has been complicated by persistent oligohydramnios. The child requires significant pulmonary support upon delivery. Which of the following clinical findings is most likely present in this child as a result of these abnormalities?
A. Clubbed feet (Correct Answer)
B. Spina bifida occulta
C. Macrosomia
D. Urachal fistula
E. Esophageal atresia
Explanation: ***Clubbed feet***
- **Oligohydramnios**, resulting from **multicystic dysplastic kidneys**, leads to reduced amniotic fluid, restricting fetal movement and causing **Potter sequence abnormalities**, including **clubfoot**.
- The lack of amniotic fluid also impairs lung development, leading to **pulmonary hypoplasia** and the need for significant respiratory support at birth.
*Spina bifida occulta*
- **Spina bifida occulta** is a neural tube defect characterized by incomplete closure of the vertebral column, often with a tuft of hair or dimple on the back, and is not directly related to oligohydramnios or renal issues.
- While it can occur as an isolated finding, it is not a characteristic component of the **Potter sequence**.
*Macrosomia*
- **Macrosomia** refers to a significantly larger-than-average baby, typically associated with conditions like **gestational diabetes**.
- It is not a feature of **Potter sequence**; in fact, chronic intrauterine stresses can sometimes lead to **intrauterine growth restriction (IUGR)** rather than macrosomia.
*Urachal fistula*
- A **urachal fistula** is a persistent connection between the bladder and the umbilicus, allowing urine to drain from the navel.
- While it is a urogenital anomaly, it is a discreet developmental defect and not a typical manifestation of the **Potter sequence** associated with bilateral multicystic dysplastic kidneys and oligohydramnios.
*Esophageal atresia*
- **Esophageal atresia** is a congenital condition where the esophagus does not develop properly, often presenting with polyhydramnios (excess amniotic fluid) due to the fetus's inability to swallow amniotic fluid.
- This is the opposite of the given clinical scenario, which involves **oligohydramnios**.
Question 189: A 9-year-old girl is brought to her pediatrician by her mother for the evaluation of recent-onset seizures. She has had 2 episodes of generalized tonic-clonic seizures in the past 3 days. Each episode lasted for 1–2 minutes and aborted spontaneously. There is no history of fever, headache, altered behavior, diarrhea, vomiting, or previous seizure episodes. Past medical history is unremarkable. Physical examination reveals: blood pressure 102/64 mm Hg, heart rate 89/min, respiratory rate 16/min, and temperature 37.0°C (98.6°F). She looks anxious but oriented to time and space. Multiple flat hyperpigmented spots are present over her body, each more than 5 mm in diameter. Axillary freckling is present. Cranial nerves are intact. Muscle strength is normal in all 4 limbs with a normal sensory examination. Gait is normal. An eye examination is shown in the exhibit. What is the most likely diagnosis?
A. Wilson disease
B. Tuberous sclerosis
C. Sturge-Weber disease
D. Neurofibromatosis type 2
E. Von Recklinghausen disease (Correct Answer)
Explanation: ***Von Recklinghausen disease***
- The combination of **generalized tonic-clonic seizures**, multiple **café-au-lait spots** (>5 mm), **axillary freckling**, and **Lisch nodules** (present in the eye examination as brown spots on the iris) is characteristic of **Neurofibromatosis type 1 (Von Recklinghausen disease)**.
- Seizures in NF1 can result from **cortical dysplasia**, gliomas, or other neurological complications.
*Wilson disease*
- Characterized by **Kayser-Fleischer rings** in the cornea (copper deposits), not Lisch nodules, and typically presents with **hepatic** and **neurological symptoms** (e.g., tremor, dysarthria, dystonia, psychiatric disturbances) not primarily hyperpigmented skin lesions.
- Seizures are less common and not associated with café-au-lait spots or axillary freckling.
*Tuberous sclerosis*
- Characterized by **ash-leaf spots** (hypopigmented macules), facial angiofibromas, shagreen patches, and periungual fibromas, along with neurologic manifestations like seizures and intellectual disability.
- **Café-au-lait spots** and **axillary freckling** are not typical features.
*Sturge-Weber disease*
- Presents with a **port-wine stain** (facial cutaneous angioma) typically in the ophthalmic division of the trigeminal nerve, **leptomeningeal angioma**, and **glaucoma**.
- **Café-au-lait spots**, axillary freckling, and Lisch nodules are not part of its diagnostic criteria.
*Neurofibromatosis type 2*
- Primarily associated with **bilateral vestibular schwannomas**, leading to hearing loss, tinnitus, and balance problems.
- While it can cause skin lesions, they are typically fewer and less prominent than in NF1, and **Lisch nodules** are not a diagnostic criterion, nor is extensive axillary freckling.
Question 190: A 4-year-old boy is brought to the pediatrician’s office for a flu-like episode. His father tells the physician that his child has fallen ill several times over the past few months. He also has occasional bouts of night sweats and loss of appetite. He has lost 5 lbs (2.3 kg) in the last 6 months. At the pediatrician’s office, his temperature is 38.9°C (102°F), pulse is 105/min and respiration rate is 18/min. On physical examination, the pediatrician observes a flattened facial profile, prominent epicanthal folds, and a single palmar crease. There are petechiae on the arms and legs. Blood count shows pancytopenia. Bone marrow aspiration is diagnostic for ALL (acute lymphoblastic leukemia), but all cells also show a trisomy. Children with similar genetic anomalies are at an increased risk of developing which of the following neurological conditions as they grow older?
A. Amyotrophic lateral sclerosis
B. Parkinson’s dementia
C. Pick’s disease
D. Lewy body dementia
E. Alzheimer’s disease (Correct Answer)
Explanation: ***Alzheimer’s disease***
- The patient's features (flattened facial profile, prominent epicanthal folds, single palmar crease) are classic for **Down syndrome (Trisomy 21)**. Individuals with Down syndrome have an increased gene dosage of the **amyloid precursor protein (APP)** gene, located on chromosome 21, leading to an earlier and higher risk of developing **Alzheimer's disease**.
- This increased APP production results in the accumulation of **amyloid-beta plaques**, a hallmark pathology of Alzheimer's disease, often starting in their 40s or 50s.
*Amyotrophic lateral sclerosis*
- **Amyotrophic lateral sclerosis (ALS)** is a progressive neurodegenerative disease affecting motor neurons, not typically associated with Down syndrome.
- While it causes muscle weakness and atrophy, it lacks the specific genetic link to Trisomy 21 and amyloid pathology seen in Alzheimer's.
*Parkinson’s dementia*
- **Parkinson's disease** is characterized by motor symptoms (tremor, rigidity, bradykinesia) and can later develop into dementia.
- It is primarily associated with the accumulation of **alpha-synuclein (Lewy bodies)**, not directly linked to Trisomy 21 or APP gene dosage.
*Pick’s disease*
- **Pick's disease** is a form of frontotemporal dementia characterized by personality changes, behavioral disinhibition, and language difficulties.
- It involves the accumulation of **tau protein aggregates (Pick bodies)** and is not specifically associated with Down syndrome.
*Lewy body dementia*
- **Lewy body dementia (LBD)** presents with fluctuating cognition, visual hallucinations, and parkinsonian features.
- The primary pathology involves **Lewy bodies (alpha-synuclein aggregates)**, which is distinct from the amyloid pathology associated with Down syndrome.
