A 4-hour-old male newborn has perioral discoloration for the past several minutes. Oxygen by nasal cannula does not improve the cyanosis. He was delivered by cesarean delivery at 37 weeks' gestation to a 38-year-old woman, gravida 3, para 2. Apgar scores were 8 and 9 at 1 and 5 minutes, respectively. The mother has type 2 diabetes mellitus that was well-controlled during the pregnancy. She has not received any immunizations since her childhood. The newborn's temperature is 37.1°C (98.8°F), pulse is 170/min, respirations are 55/min, and blood pressure is 80/60 mm Hg. Pulse oximetry shows an oxygen saturation of 85%. Cardiopulmonary examination shows a 2/6 holosystolic murmur along the lower left sternal border. The abdomen is soft and non-tender. Echocardiography shows pulmonary arteries arising from the posterior left ventricle, and the aorta rising anteriorly from the right ventricle. Which of the following is the most appropriate next step in the management of this patient?
Q142
A 10-year-old boy is brought to a family physician by his mother with a history of recurrent headaches. The headaches are moderate-to-severe in intensity, unilateral, mostly affecting the left side, and pulsatile in nature. Past medical history is significant for mild intellectual disability and complex partial seizures that sometimes progress to secondary generalized seizures. He was adopted at the age of 7 days. His birth history and family history are not available. His developmental milestones were slightly delayed. There is no history of fever or head trauma. His vital signs are within normal limits. His height and weight are at the 67th and 54th percentile for his age. Physical examination reveals an area of bluish discoloration on his left eyelid and cheek. The rest of the examination is within normal limits. A computed tomography (CT) scan of his head is shown in the exhibit. Which of the following additional clinical findings is most likely to be present?
Q143
A 1-week-old baby is brought to the pediatrician’s office for a routine checkup. On examination, she is observed to have microcephaly with a prominent occiput. She also has clenched fists and rocker-bottom feet with prominent calcanei. A cardiac murmur is evident on auscultation. Based on the clinical findings, a diagnosis of nondisjunction of chromosome 18 is suspected. The pediatrician orders a karyotype for confirmation. He goes on to explain to the mother that her child will face severe growth difficulties. Even if her daughter progresses beyond a few months, she will not be able to reach developmental milestones at the appropriate age. In addition to the above, which of the following is most likely a consequence of this genetic disturbance?
Q144
An 8-year-old child with “elfin” facial features is very friendly with strangers. He has a history of mild mental retardation, and a hemizygous deletion on chromosome 7q11.23, that includes a portion of the elastin gene. Which of the following is most likely true in this patient?
Q145
A 15-year-old boy is brought to the physician by his mother for a well-child examination. He recently stopped attending his swim classes. The patient is at the 97th percentile for height and the 50th percentile for weight. Examination shows decreased facial hair, bilateral breast enlargement, and long extremities. Genital examination shows scant pubic hair, small testes, and a normal-sized penis. Further evaluation is most likely to show which of the following karyotypes?
Q146
A 5-year-old girl is brought to the emergency department by her mother with seizures. The blood glucose is 94 mg/dl and the serum calcium is 5.3 mg/dl; however, the PTH levels are low. The medical history includes a delay in achieving developmental milestones. Her mother also says she needs frequent hospital visits due to recurrent bouts with the flu. The cardiovascular examination is within normal limits. What is the most likely cause underlying this presentation?
Q147
A 14-year-old boy is brought to the physician because of increasing swelling of his legs and generalized fatigue for 1 month. During this period he has also had a productive cough and shortness of breath. He has been unable to carry out his daily activities. He has a history of recurrent respiratory tract infections and chronic nasal congestion since childhood. He has a 3-month history of foul-smelling and greasy stools. He is at 4th percentile for height and weight. His temperature is 37°C (98.6°F), pulse is 112/min, respirations are 23/min, and blood pressure is 104/64 mm Hg. Examination shows clubbing of his fingers and scoliosis. There is 2+ pitting edema of the lower extremities. Jugular venous distention is present. Inspiratory crackles are heard in the thorax. Cardiac examination shows a loud S2. The abdomen is mildly distended and the liver is palpated 2 cm below the right costal margin. Hepato-jugular reflux is present. Which of the following is the most likely diagnosis?
Q148
A 6-year-old male presents to the pediatrician with seizures. His mother reports that the patient has had two seizures lasting about 30 seconds each over the last three days. She reports that the patient has previously had seizures a few times per year since he was 12 months of age. The patient’s past medical history is otherwise notable for intellectual disability. He rolled over at 14 months of age and walked at 24 months of age. The patient’s mother denies any family history of epilepsy or other neurologic diseases. The patient is in the 3rd percentile for height and the 15th percentile for weight. On physical exam, he has a happy demeanor with frequent smiling. The patient has strabismus and an ataxic gait accompanied by flapping of the hands. He responds intermittently to questions with one-word answers. This patient is most likely to have which of the following genetic abnormalities?
Q149
A 4-month-old male infant is brought to the physician by his father because of swelling of his left hemiscrotum. He has otherwise been healthy and is gaining weight appropriately. Physical examination shows a nontender left scrotal mass that transilluminates. The mass increases in size when the boy cries but is easily reducible. Which of the following is the most likely underlying cause of this patient's findings?
Q150
An inconsolable mother brings her 2-year-old son to the emergency room after finding a large amount of bright red blood in his diaper, an hour ago. She states that for the past week her son has been having crying fits while curling his legs towards his chest in a fetal position. His crying resolves either after vomiting or passing fecal material. Currently, the child is in no apparent distress. Physical examination with palpation in the gastric region demonstrates no acute findings. X-ray of the abdominal area demonstrates no acute findings. His current temperature is 36.5°C (97.8°F), heart rate is 93/min, blood pressure is 100/64 mm Hg, and respiratory rate is 26/min. His weight is 10.8 kg (24.0 lb), and height is 88.9 cm (35.0 in). Laboratory tests show the following:
RBC count 5 million/mm3
Hematocrit 36%
Hemoglobin 12 g/dL
WBC count 6,000/mm3
Mean corpuscular volume 78 fL
What is the most likely underlying embryological cause predisposing to this condition?
Congenital defects US Medical PG Practice Questions and MCQs
Question 141: A 4-hour-old male newborn has perioral discoloration for the past several minutes. Oxygen by nasal cannula does not improve the cyanosis. He was delivered by cesarean delivery at 37 weeks' gestation to a 38-year-old woman, gravida 3, para 2. Apgar scores were 8 and 9 at 1 and 5 minutes, respectively. The mother has type 2 diabetes mellitus that was well-controlled during the pregnancy. She has not received any immunizations since her childhood. The newborn's temperature is 37.1°C (98.8°F), pulse is 170/min, respirations are 55/min, and blood pressure is 80/60 mm Hg. Pulse oximetry shows an oxygen saturation of 85%. Cardiopulmonary examination shows a 2/6 holosystolic murmur along the lower left sternal border. The abdomen is soft and non-tender. Echocardiography shows pulmonary arteries arising from the posterior left ventricle, and the aorta rising anteriorly from the right ventricle. Which of the following is the most appropriate next step in the management of this patient?
A. Indomethacin administration
B. Surgical repair
C. Obtain a CT Angiography
D. Reassurance
E. Prostaglandin E1 administration (Correct Answer)
Explanation: ***Prostaglandin E1 administration***
- The echocardiogram findings of **pulmonary arteries arising from the posterior left ventricle** and the **aorta rising anteriorly from the right ventricle** are characteristic of **transposition of the great arteries (TGA)**.
- In TGA, **prostaglandin E1** is crucial to maintain patency of the **ductus arteriosus**, which provides a mixing site for oxygenated and deoxygenated blood, improving systemic oxygenation.
*Indomethacin administration*
- **Indomethacin** is used to **close** a patent ductus arteriosus, which would be detrimental in a patient with TGA as ductal patency is required for survival.
- Closing the ductus arteriosus in TGA would severely restrict blood mixing and worsen cyanosis.
*Surgical repair*
- While surgery (arterial switch operation) is the definitive treatment for TGA, it is not the *immediate* next step for a cyanotic neonate.
- **Stabilization** with prostaglandin E1 to improve oxygenation is required before proceeding with surgery.
*Obtain a CT Angiography*
- An **echocardiogram** has already definitively diagnosed the cardiac anomaly (TGA).
- A CT angiography is not typically required for initial diagnosis or acute management of TGA and would expose the neonate to unnecessary radiation.
*Reassurance*
- The newborn has significant **cyanosis (85% oxygen saturation)** and a serious congenital heart defect (TGA), requiring immediate medical intervention.
- Reassurance is inappropriate given the critical condition of the neonate and the need for urgent treatment.
Question 142: A 10-year-old boy is brought to a family physician by his mother with a history of recurrent headaches. The headaches are moderate-to-severe in intensity, unilateral, mostly affecting the left side, and pulsatile in nature. Past medical history is significant for mild intellectual disability and complex partial seizures that sometimes progress to secondary generalized seizures. He was adopted at the age of 7 days. His birth history and family history are not available. His developmental milestones were slightly delayed. There is no history of fever or head trauma. His vital signs are within normal limits. His height and weight are at the 67th and 54th percentile for his age. Physical examination reveals an area of bluish discoloration on his left eyelid and cheek. The rest of the examination is within normal limits. A computed tomography (CT) scan of his head is shown in the exhibit. Which of the following additional clinical findings is most likely to be present?
A. Glaucoma (Correct Answer)
B. Ash leaf spots
C. Charcot-Bouchard aneurysm
D. Café-au-lait spots
E. Iris hamartoma
Explanation: ***Glaucoma***
- The clinical presentation, including recurrent headaches, complex partial seizures, developmental delay, and a **bluish discoloration on the left eyelid and cheek (facial port-wine stain)**, along with the CT scan showing **cortical calcifications**, is highly suggestive of **Sturge-Weber syndrome**.
- **Glaucoma** is a common ocular manifestation of Sturge-Weber syndrome, particularly on the ipsilateral side of the facial port-wine stain, due to abnormal episcleral vasculature.
*Ash leaf spots*
- **Ash leaf spots** are hypopigmented macules characteristic of **Tuberous Sclerosis Complex**, which also manifests with seizures and intellectual disability but not typically with a facial port-wine stain or cortical calcifications in this pattern.
- While both Sturge-Weber and Tuberous Sclerosis are **neurocutaneous syndromes**, their specific diagnostic features differ.
*Charcot-Bouchard aneurysm*
- **Charcot-Bouchard aneurysms** are small aneurysms that occur in the brain's small penetrating arteries, typically associated with **chronic hypertension**, and can cause **intracerebral hemorrhage**.
- They are not related to the clinical picture of a facial port-wine stain, seizures, or developmental delay seen in this patient.
*Café-au-lait spots*
- **Café-au-lait spots** are hyperpigmented macules and are a hallmark feature of **Neurofibromatosis Type 1 (NF1)**, which is also associated with seizures and developmental delays.
- However, NF1 does not typically present with the facial port-wine stain or the specific cortical calcifications seen in Sturge-Weber syndrome.
*Iris hamartoma*
- **Iris hamartomas**, also known as **Lisch nodules**, are characteristic ocular findings in **Neurofibromatosis Type 1 (NF1)**.
- While NF1 can involve seizures and developmental delays, it does not present with a facial port-wine stain or the typical brain calcifications of Sturge-Weber syndrome.
Question 143: A 1-week-old baby is brought to the pediatrician’s office for a routine checkup. On examination, she is observed to have microcephaly with a prominent occiput. She also has clenched fists and rocker-bottom feet with prominent calcanei. A cardiac murmur is evident on auscultation. Based on the clinical findings, a diagnosis of nondisjunction of chromosome 18 is suspected. The pediatrician orders a karyotype for confirmation. He goes on to explain to the mother that her child will face severe growth difficulties. Even if her daughter progresses beyond a few months, she will not be able to reach developmental milestones at the appropriate age. In addition to the above, which of the following is most likely a consequence of this genetic disturbance?
A. Supravalvular aortic stenosis
B. Alzheimer’s disease
C. Macroglossia
D. Cutis aplasia
E. Death within the first year of life (Correct Answer)
Explanation: ***Death within the first year of life***
- This patient has Trisomy 18, also known as Edwards syndrome, which is characterized by a high mortality rate, with **90-95% of affected infants dying within the first year** due to severe congenital anomalies, especially cardiac defects.
- **Rocker-bottom feet**, **clenched fists with overlapping fingers**, **microcephaly with a prominent occiput**, and **congenital heart defects** (such as ventricular septal defects or patent ductus arteriosus) are classic features of Trisomy 18.
*Cutis aplasia*
- **Cutis aplasia** (a congenital absence of skin) is a characteristic symptom of **Trisomy 13 (Patau syndrome)**, not Trisomy 18.
- While both are chromosomal abnormalities, their specific phenotypic presentations differ, making cutis aplasia less likely in this case.
*Macroglossia*
- **Macroglossia** (an enlarged tongue) is a common feature of **Down syndrome (Trisomy 21)**.
- It is not typically associated with Trisomy 18, which presents with distinct facial and oral features.
*Alzheimer’s disease*
- Individuals with **Down syndrome (Trisomy 21)** have an increased risk of developing **early-onset Alzheimer's disease**, often by middle age.
- This is due to the triplication of the **APP gene**, located on chromosome 21, which is involved in amyloid-beta plaque formation.
*Supravalvular aortic stenosis*
- **Supravalvular aortic stenosis** (narrowing of the aorta above the aortic valve) is a characteristic cardiac finding in **Williams syndrome**, a microdeletion syndrome involving chromosome 7.
- Williams syndrome is also associated with elfin facies, intellectual disability, and a friendly personality, none of which align with this patient's presentation.
Question 144: An 8-year-old child with “elfin” facial features is very friendly with strangers. He has a history of mild mental retardation, and a hemizygous deletion on chromosome 7q11.23, that includes a portion of the elastin gene. Which of the following is most likely true in this patient?
A. Vitamin D supplementation is recommended
B. Symptoms may develop secondary to left ventricular outflow tract obstruction (Correct Answer)
C. This patient is less likely to experience angina
D. Holosystolic murmur heard at the apex with radiation to the axilla
E. Carpopedal spasm induced by sphygmomanometer inflation
Explanation: ***Symptoms may develop secondary to left ventricular outflow tract obstruction***
* The clinical description of **elfin facies**, extreme friendliness, mild mental retardation, and a deletion on **chromosome 7q11.23** (involving the **elastin gene**) are classic features of **Williams syndrome**.
* **Supravalvular aortic stenosis (SVAS)**, a form of left ventricular outflow tract obstruction, is a common and serious cardiac anomaly in Williams syndrome due to the elastin gene deletion.
*Vitamin D supplementation is recommended*
* Patients with Williams syndrome often experience **hypercalcemia** in infancy, making vitamin D supplementation generally contraindicated rather than recommended.
* This hypercalcemia usually resolves spontaneously in later childhood.
*This patient is less likely to experience angina*
* Due to the high prevalence of **supravalvular aortic stenosis** and other vascular abnormalities in Williams syndrome, these patients are actually **more likely** to experience cardiovascular symptoms, including **angina**, especially with physical exertion.
* Stenosis can lead to increased myocardial oxygen demand, potentially causing angina.
*Holosystolic murmur heard at the apex with radiation to the axilla*
* A holosystolic murmur at the apex radiating to the axilla is characteristic of **mitral regurgitation**, which is not the primary or most common cardiac anomaly in Williams syndrome.
* The characteristic murmur in Williams syndrome due to supravalvular aortic stenosis is typically a **systolic ejection murmur** heard best in the right upper sternal border, often radiating to the neck.
*Carpopedal spasm induced by sphygmomanometer inflation*
* **Carpopedal spasm** induced by sphygmomanometer inflation (Trousseau's sign) is indicative of **hypocalcemia**.
* Patients with Williams syndrome typically experience **hypercalcemia**, not hypocalcemia, particularly during infancy.
Question 145: A 15-year-old boy is brought to the physician by his mother for a well-child examination. He recently stopped attending his swim classes. The patient is at the 97th percentile for height and the 50th percentile for weight. Examination shows decreased facial hair, bilateral breast enlargement, and long extremities. Genital examination shows scant pubic hair, small testes, and a normal-sized penis. Further evaluation is most likely to show which of the following karyotypes?
A. 45,XO/46,XX
B. 45,XO
C. 47,XYY
D. 46,XX/46,XY
E. 47,XXY (Correct Answer)
Explanation: ***47,XXY***
- The patient's presentation with **tall stature**, **gynecomastia**, **small testes**, and **scant pubic hair** is characteristic of **Klinefelter syndrome**, which is caused by a **47,XXY karyotype**.
- **Hypogonadism** in Klinefelter syndrome leads to **decreased testosterone production**, explaining the lack of facial hair and undeveloped secondary sexual characteristics.
*45,XO/46,XX*
- This mosaic karyotype is associated with **Turner syndrome**, which primarily affects females and presents with features like **short stature**, **gonadal dysgenesis**, and **webbed neck**.
- Males with this karyotype are rare and would not exhibit the typical features described, such as **gynecomastia** and eunuchoid body habitus.
*45,XO*
- This is the classic karyotype for **Turner syndrome**, which is exclusively found in phenotypic females.
- Individuals with 45,XO present with **short stature**, **streak gonads**, and a lack of secondary sexual characteristics, none of which align with the male patient's symptoms.
*47,XYY*
- Individuals with **XYY syndrome** (Jacob syndrome) are typically **tall** but usually have **normal sexual development** and **fertility**.
- This karyotype does not explain the **gynecomastia**, **small testes**, or **decreased facial hair** seen in the patient.
*46,XX/46,XY*
- This karyotype indicates **gonadal mosaicism**, also known as **ovotesticular disorder of sex development (DSD)** or **chimerism**, where an individual has both ovarian and testicular tissue.
- While it can present with ambiguous genitalia and mixed secondary sexual characteristics, the specific constellation of **tall stature**, **gynecomastia**, and **small testes** is more indicative of Klinefelter syndrome.
Question 146: A 5-year-old girl is brought to the emergency department by her mother with seizures. The blood glucose is 94 mg/dl and the serum calcium is 5.3 mg/dl; however, the PTH levels are low. The medical history includes a delay in achieving developmental milestones. Her mother also says she needs frequent hospital visits due to recurrent bouts with the flu. The cardiovascular examination is within normal limits. What is the most likely cause underlying this presentation?
A. Deletion of the chromosome 22q11 (Correct Answer)
B. Mutation in the WAS gene
C. B cell development failure
D. B cell maturation failure
E. Lysosomal trafficking regulator gene defect
Explanation: ***Deletion of the chromosome 22q11***
- The combination of **hypocalcemia with low PTH** (due to **parathyroid hypoplasia**), recurrent infections (due to **thymic hypoplasia** leading to T-cell deficiency), and developmental delay is classic for **DiGeorge syndrome**.
- **DiGeorge syndrome** is caused by a **microdeletion on chromosome 22q11.2**, affecting the development of structures derived from the **third and fourth pharyngeal pouches**.
*Mutation in the WAS gene*
- A mutation in the **WAS gene** causes **Wiskott-Aldrich syndrome**, characterized by **thrombocytopenia**, **eczema**, and **recurrent infections**.
- It does not directly explain the **hypocalcemia with low PTH** or developmental delay present in this patient.
*B cell development failure*
- **B-cell development failure**, as seen in conditions like **X-linked agammaglobulinemia**, leads to recurrent bacterial infections due to absent antibodies.
- However, it does not account for the **hypocalcemia** or developmental delay observed.
*B cell maturation failure*
- **B-cell maturation failure** results in impaired antibody production and recurrent infections but typically does not present with **hypocalcemia and low PTH** or developmental delay.
- Conditions like **Common Variable Immunodeficiency (CVID)** involve mature B cells failing to differentiate into plasma cells.
*Lysosomal trafficking regulator gene defect*
- A defect in the **lysosomal trafficking regulator gene (LYST)** is associated with **Chediak-Higashi syndrome**, which involves impaired lysosomal function, leading to immunodeficiency, **partial albinism**, and neurological abnormalities.
- This condition does not typically present with **hypocalcemia** or the specific constellation of symptoms seen in this case.
Question 147: A 14-year-old boy is brought to the physician because of increasing swelling of his legs and generalized fatigue for 1 month. During this period he has also had a productive cough and shortness of breath. He has been unable to carry out his daily activities. He has a history of recurrent respiratory tract infections and chronic nasal congestion since childhood. He has a 3-month history of foul-smelling and greasy stools. He is at 4th percentile for height and weight. His temperature is 37°C (98.6°F), pulse is 112/min, respirations are 23/min, and blood pressure is 104/64 mm Hg. Examination shows clubbing of his fingers and scoliosis. There is 2+ pitting edema of the lower extremities. Jugular venous distention is present. Inspiratory crackles are heard in the thorax. Cardiac examination shows a loud S2. The abdomen is mildly distended and the liver is palpated 2 cm below the right costal margin. Hepato-jugular reflux is present. Which of the following is the most likely diagnosis?
A. Goodpasture syndrome
B. Hypertrophic cardiomyopathy
C. Cystic fibrosis (Correct Answer)
D. Minimal change disease
E. Protein malnutrition
Explanation: ***Cystic fibrosis***
- Chronic respiratory symptoms (productive cough, recurrent infections, crackles, shortness of breath), malabsorption (foul-smelling, greasy stools, poor growth), and signs of right-sided heart failure (edema, JVD, hepatomegaly, loud S2 indicating **pulmonary hypertension**) are all classic manifestations of **cystic fibrosis**.
- The combination of **respiratory, gastrointestinal, and cardiac involvement** in a child with a history of chronic respiratory issues and poor growth strongly points to this diagnosis.
*Goodpasture syndrome*
- Characterized by rapidly progressive **glomerulonephritis** and **pulmonary hemorrhage**, presenting with hemoptysis and renal dysfunction.
- While it affects lungs, it does not typically cause chronic respiratory infections, malabsorption, or right-sided heart failure in this manner.
*Hypertrophic cardiomyopathy*
- Primarily a genetic disorder causing thickening of the heart muscle, leading to **diastolic dysfunction** and outflow obstruction.
- It would not explain the chronic respiratory infections, malabsorption, or the systemic edema and JVD suggestive of right heart failure secondary to chronic lung disease.
*Minimal change disease*
- A cause of **nephrotic syndrome** in children, characterized by proteinuria, hypoalbuminemia, and edema.
- While it causes significant edema, it does not explain the chronic respiratory symptoms, malabsorption, or the clear signs of cardiac and pulmonary involvement.
*Protein malnutrition*
- Can cause **edema** due to low oncotic pressure (kwashiorkor), and may lead to poor growth and increased susceptibility to infections.
- However, it would not directly cause the specific chronic respiratory symptoms, productive cough, or the obstructive lung disease often indicated by signs of pulmonary hypertension.
Question 148: A 6-year-old male presents to the pediatrician with seizures. His mother reports that the patient has had two seizures lasting about 30 seconds each over the last three days. She reports that the patient has previously had seizures a few times per year since he was 12 months of age. The patient’s past medical history is otherwise notable for intellectual disability. He rolled over at 14 months of age and walked at 24 months of age. The patient’s mother denies any family history of epilepsy or other neurologic diseases. The patient is in the 3rd percentile for height and the 15th percentile for weight. On physical exam, he has a happy demeanor with frequent smiling. The patient has strabismus and an ataxic gait accompanied by flapping of the hands. He responds intermittently to questions with one-word answers. This patient is most likely to have which of the following genetic abnormalities?
A. Chromosomal macrodeletion on chromosome 5
B. Maternal uniparental disomy of chromosome 15
C. Imprinting defect on chromosome 11
D. Trinucleotide repeat disorder
E. Paternal uniparental disomy of chromosome 15 (Correct Answer)
Explanation: ***Paternal uniparental disomy of chromosome 15***
- The patient's presentation with **intellectual disability**, **seizures**, developmental delay (rolling over at 14 months, walking at 24 months), **ataxic gait**, **happy demeanor** with frequent smiling, and hand flapping are classic features of **Angelman syndrome**.
- **Angelman syndrome** requires loss of function of the maternal UBE3A gene on chromosome 15, which is paternally imprinted (meaning only the maternal copy is active).
- **Paternal uniparental disomy** means both copies of chromosome 15 come from the father, resulting in no functional maternal UBE3A gene, causing Angelman syndrome.
- Other causes include maternal deletion of 15q11-q13 (most common), imprinting defects, and UBE3A mutations.
*Maternal uniparental disomy of chromosome 15*
- This causes **Prader-Willi syndrome**, not Angelman syndrome.
- When both chromosome 15s come from the mother, there is no paternal contribution, and paternally expressed genes are lost.
- Prader-Willi presents with **neonatal hypotonia**, **feeding difficulties**, later **hyperphagia** and **obesity**, which are not seen in this patient.
*Imprinting defect on chromosome 11*
- This is associated with **Beckwith-Wiedemann syndrome**, which presents with **macroglossia**, **omphalocele**, **hemihyperplasia**, and increased tumor risk.
- The clinical presentation is distinctly different from this patient's features.
*Trinucleotide repeat disorder*
- Includes conditions such as **Fragile X syndrome**, **Huntington's disease**, and **Myotonic dystrophy**.
- Fragile X syndrome can cause intellectual disability and seizures but typically presents with **macroorchidism** (in post-pubertal males), long face, large ears, and **autistic features** rather than the happy demeanor seen here.
*Chromosomal macrodeletion on chromosome 5*
- This is characteristic of **Cri du Chat syndrome** (5p deletion).
- Presents with a distinctive **cat-like cry**, **microcephaly**, widely spaced eyes, and severe intellectual disability, which do not match this patient's presentation.
Question 149: A 4-month-old male infant is brought to the physician by his father because of swelling of his left hemiscrotum. He has otherwise been healthy and is gaining weight appropriately. Physical examination shows a nontender left scrotal mass that transilluminates. The mass increases in size when the boy cries but is easily reducible. Which of the following is the most likely underlying cause of this patient's findings?
A. Lack of testicular fixation
B. Sperm collection in epididymal duct
C. Dilation of pampiniform plexus
D. Patent processus vaginalis (Correct Answer)
E. Germ cell neoplasia
Explanation: ***Patent processus vaginalis***
- A **patent processus vaginalis** allows peritoneal fluid to flow into the scrotum, causing a **hydrocele** that **transilluminates** and a potential **indirect inguinal hernia** if abdominal contents protrude.
- The mass increasing with crying and being easily reducible, alongside transillumination, are classic signs of an **indirect inguinal hernia** or a **communicating hydrocele**, both stemming from a patent processus vaginalis.
*Lack of testicular fixation*
- This condition is associated with **testicular torsion**, which typically presents with sudden onset of severe scrotal pain, testicular tenderness, and lack of transillumination.
- The patient's symptoms (non-tender, transilluminating, reducible mass) are not consistent with **testicular torsion**.
*Sperm collection in epididymal duct*
- This describes a **spermatocele**, which is rare in infants and typically presents as a non-tender, firm cyst proximal to the testis, often not reducible or fluctuating with crying.
- Spermatoceles are more common in older males and often do not transilluminate as clearly as hydroceles.
*Dilation of pampiniform plexus*
- This refers to a **varicocele**, which is a collection of dilated veins in the scrotum, typically described as a "bag of worms" and usually does not transilluminate.
- Varicoceles are rare in infants and more commonly present in adolescents and adults.
*Germ cell neoplasia*
- **Testicular tumors** in infants are very rare and would typically present as a firm, non-tender, non-transilluminating mass that is not reducible.
- While swelling is a symptom, the other characteristics (transillumination, reducibility, increase with crying) are not typical for a neoplastic process.
Question 150: An inconsolable mother brings her 2-year-old son to the emergency room after finding a large amount of bright red blood in his diaper, an hour ago. She states that for the past week her son has been having crying fits while curling his legs towards his chest in a fetal position. His crying resolves either after vomiting or passing fecal material. Currently, the child is in no apparent distress. Physical examination with palpation in the gastric region demonstrates no acute findings. X-ray of the abdominal area demonstrates no acute findings. His current temperature is 36.5°C (97.8°F), heart rate is 93/min, blood pressure is 100/64 mm Hg, and respiratory rate is 26/min. His weight is 10.8 kg (24.0 lb), and height is 88.9 cm (35.0 in). Laboratory tests show the following:
RBC count 5 million/mm3
Hematocrit 36%
Hemoglobin 12 g/dL
WBC count 6,000/mm3
Mean corpuscular volume 78 fL
What is the most likely underlying embryological cause predisposing to this condition?
A. Failure of the vitelline duct to close (Correct Answer)
B. Failure of the vitelline duct to open
C. Elevated anti-mitochondrial antibodies
D. Problem with bilirubin conjugation
E. Problem with bilirubin uptake
Explanation: ***Failure of the vitelline duct to close***
- The clinical presentation of a 2-year-old with recurrent episodes of abdominal pain, crying spells (curling legs to chest), and the passage of bright red blood in the diaper is highly suggestive of **intussusception**. This can be transiently relieved when the "curled" bowel straightens itself out, or gas/fecal matter is passed. The presence of **bright red blood** (often referred to as **currant jelly stools** when mixed with mucus) further supports this diagnosis, indicating ischemic bowel.
- In children, intussusception is often idiopathic, but in a small percentage of cases, especially in older infants and children, an **anatomical lead point** can cause it. The most common anatomical lead point is a **Meckel's diverticulum**, which results from the **incomplete obliteration of the vitelline duct** (also known as the omphalomesenteric duct) during embryological development. The diverticulum can act as a foreign body that then telescopes into the adjacent bowel, causing intussusception.
*Failure of the vitelline duct to open*
- The vitelline duct should normally regress and disappear. Therefore, a "failure to open" is not a recognized embryological anomaly or pathology.
- Problems related to the vitelline duct involve either its **incomplete closure** (leading to Meckel's diverticulum, vitelline cysts, or fistulas) or other abnormal remnants, not a failure to open.
*Elevated anti-mitochondrial uptake*
- This option refers to **anti-mitochondrial antibodies (AMAs)**, which are characteristic markers for **primary biliary cholangitis (PBC)**, an autoimmune disease primarily affecting the liver.
- PBC is an adult-onset condition and is not associated with intussusception or the gastrointestinal symptoms described in the child.
*Problem with bilirubin conjugation*
- Issues with **bilirubin conjugation** primarily manifest as different types of **jaundice** (e.g., Crigler-Najjar syndrome, Gilbert's syndrome) due to the accumulation of unconjugated bilirubin.
- These conditions do not cause abdominal pain, intussusception, or bloody stools.
*Problem with bilirubin uptake*
- Problems with **bilirubin uptake** by hepatocytes also lead to **unconjugated hyperbilirubinemia** and jaundice.
- This condition is unrelated to acute abdominal emergencies like intussusception or gastrointestinal bleeding.
