10 USMLE Pediatrics and Genetics Questions with Answers and Explanations (Set 1)

These 10 USMLE pediatrics and genetics practice questions cover newborn and childhood conditions that repeat on the exam: tracheoesophageal fistula, craniopharyngioma, Turner syndrome, Lesch-Nyhan syndrome, von Gierke disease, hemolytic uremic syndrome, cystic fibrosis, iron deficiency in premature infants and retinoblastoma. Each question includes the correct answer and an explanation.

Written by Dr. Ray Makar, MD, author of the Repeated USMLE Questions eBook series.

Prefer video? Watch daily USMLE case questions on MedFocus by Dr. Ray on YouTube.

How to use this page: read the question, pick your answer, then tap Show Answer and Explanation.

Questions

Question 1. A 1-day-old full-term baby of a 23-year old mother who was delivered yesterday by normal vaginal delivery is coughing, choking, and ejecting the formula from his nose and mouth. He also turns blue during feeding. What is the primary diagnosis of this boy?

A- Imperforate anus
B- Pyloric stenosis
C- Tetralogy of Fallot
D- Tracheoesophageal fistula
E- Tracheomalacia

A newborn with coughing, choking, and cyanosis during feeding is classic for tracheoesophageal fistula (TEF). Milk coming out of the nose and mouth suggests that swallowed feeds cannot pass normally into the stomach. The symptoms occur immediately after birth and during feeds, which is typical for TEF (often with esophageal atresia).
Imperforate anus presents with failure to pass meconium and abdominal distension, not feeding-related cyanosis. Pyloric stenosis occurs at 2–8 weeks of age with projectile, non-bilious vomiting. Tetralogy of Fallot causes cyanosis, but not specifically during feeding with choking. Tracheomalacia causes stridor and breathing difficulty, not milk regurgitation through the nose.
The correct answer is D
Key takeaway:👉 Coughing, choking, and cyanosis during feeding in a newborn = tracheoesophageal fistula.

 

Question 2. A 6-year-old girl is brought to her pediatrician by her mother for consultation. She said that her daughter is frequently bumping into chairs while walking or playing. On examination, she is found to have bitemporal hemianopia. CT scan shows calcification in the pituitary fossa. What is the most likely diagnosis of this condition?

A- Choriocarcinoma
B- Craniopharyngioma
C- Gangliocytoma
D- Germinoma
E- Teratoma

This child’s symptoms are classic for craniopharyngioma.
Bitemporal hemianopia indicates compression of the optic chiasm, which lies just above the pituitary.
Calcification in the pituitary (sellar/suprasellar) region on CT is a hallmark finding of craniopharyngioma.
It is one of the most common suprasellar tumors in children.
It arises from Rathke’s pouch remnants and often has cystic and calcified components.
Why not the others?
Choriocarcinoma, germinoma, and teratoma are germ cell tumors and are less commonly associated with calcified pituitary masses in young children.
Gangliocytoma is rare and usually presents with hormone hypersecretion rather than visual field defects.
The correct answer is B
Key takeaway:Child + bitemporal hemianopia + calcified sellar/suprasellar mass = Craniopharyngioma.

 

Question 3. A 34-year old woman delivered a girl at her 37-week gestational age through a normal delivery two hours ago. Examination of the newborn girl reveals pink skin, red reflex in both eyes, high arched palate, webbed neck, swollen hands and feet and widely spaced nipples. Heart and lungs auscultation is unremarkable except for a systolic murmur below the left scapula. Which of the following congenital heart diseases is most likely found in this patient?

A- Atrial septal defect
B- Ventricular septal defect
C- Coarctation of the aorta
D- Tetralogy of Fallot
E- Transposition of great vessels

This presentation is typical for Turner’s syndrome. Coarctation of the aorta is the most common congenital heart disease seen in this condition.
The correct answer is C
To see the previous question Go Here

 

Question 4. A 4-year-old boy is brought to his physician by his mother. She is worried and tells you that her son is weak and not growing properly. He chews his fingers and lips constantly and seems to enjoy it. On examination, there is marked loss of tissues on his fingers and lips. His serum and urine levels of uric acid are both high. What is the most likely diagnosis of this condition?

A- Gaucher disease
B- Hurler syndrome
C- Lesch-Nyhan syndrome
D- Galactosemia
E- Tay-sachs disease

This is a typical presentation of Lesch-Nyhan syndrome which is caused by hypoxanthine-guanine phosphoribosyltransferase (HGPRT) enzyme deficiency. Elevated serum and urine uric acid concentrations accompanied by self-mutilating behaviors are diagnostic of this condition.
The correct answer is C

 

Question 5. A 2-month-old child is brought to the clinic by his parents with a complaint of failure to thrive. During an examination, the baby suffers a seizure. Test of stat serum chemistries indicates hyperlipidemia, severe hypoglycemia, ketosis, and lactic acidosis. Hepatomegaly is also confirmed by both physical examination and CT scan. Which of the following conditions is the child suffering from based on these findings?

A- Gaucher disease
B- Niemann-Pick disease
C- Pompe disease
D- Von Gierke disease

Also known as glycogen storage disease type 1, Von Gierke disease, is a condition where the body is unable to break down glycogen, which is a form of glucose (sugar) that is stored in muscles and liver. Glycogen is broken down into glucose to give more energy through glycogenolysis. The condition is marked by low blood sugar, slow growth rate, weak muscles, enlarged liver, heat intolerance, etc.
The correct answer is D

 

Question 6. A 3-year-old boy is brought to the emergency room by his mother for vomiting and bloody diarrhea for 4 days. She also noticed low urinary output in the past 2 days. He had no similar attacks in the past and his medical and family histories are unremarkable. On examination, his vital signs are within normal limits, no signs of dehydration, no abdominal tenderness or organomegaly and no rashes or any skin manifestations of hemorrhage or internal disease. Laboratory tests reveal mild anemia, thrombocytopenia and abundant reticulocytes and schistocytes. Urinalysis reveals red blood cells with no casts. Kidney function tests reveal marked increase in serum urea and creatinine. Coagulation profile is normal. Stool Shiga toxin test is positive for Shiga toxin 2. What is the most likely diagnosis?

A- Idiopathic thrombocytopenic purpura
B- Thrombocytopenic thrombotic purpura
C- Henoch-Schonlein purpura
D- Hemolytic uremic syndrome
E- Renal stones

The triad of hemolytic anemia, acute kidney failure and thrombocytopenia is characteristic of hemolytic uremic syndrome. Also, positive Shiga toxin is confirmatory for diagnosis of HUS.
The correct answer is D

 

Question 7. As physicians, we need to know some definitions in Genetics, which are related directly to our practice and guide us to diagnose and treat many genetic disorders. These items include genome, genotype, phenotype, genetic code, gene expression, etc. Which one of the following choices describes the definition of a phenotype?

A- Genetic history of an organism
B- DNA structure that determines the expression of a trait
C- An observable physical or biochemical trait on an organism
D- Physical location of a trait on a DNA molecule

Phenotype is the observable physical or biochemical features that seen on an organism featuring the expression of genotype.
The correct answer is C

 

Question 8. A 9-month-old boy is brought to the pediatrician for persistent cough, poor weight gain, and several bouts of pneumonitis. Upon taking history from his mother, she mentions that her boy had been also having foul-smelling and very large stools for a few months. Which of the following diagnostic techniques will help to provide the correct diagnosis of this condition?

A- TB skin test
B- CT of the chest
C- Serum immunoglobulins
D- Sweat chloride test

Keeping the symptoms of the baby in mind, this is most likely a case of cystic fibrosis, which generally presents during infancy with poor growth and recurrent respiratory and/or intestinal disorders. The sweat chloride test is one of the most common diagnostic tests used to evaluate a patient if you suspect cystic fibrosis. Cystic fibrosis impacts the manner in which chloride moves in and out of cells. As sweat contains chloride in the form of sodium chloride, sweat chloride test is used as the standard method for diagnosing cystic fibrosis.
The correct answer is D

 

Question 9. A 3-month-old girl is brought to the clinic due to weakness and pallor for one week. History claims that she was born after premature delivery. She is normal in development and growth. She is breastfed and her immunizations are up to date. What is the most appropriate treatment?

A- Milk formula instead of breastfeeding
B- Iron supplement
C- Vitamin C supplement
D- Vitamin D supplement

Iron supplementation in the form of iron-fortified formula or oral ferrous sulfate is recommended to prevent anemia especially in premature infants. Breastfeeding is still recommended for its benefits. Vitamin C should be added to diet at 6-month of age. Vitamin D is used in cases of deficiency and in certain cases later in life.
The correct answer is B

 

Question 10. A 4-month-old boy is brought to the pediatrician by his parents who are concerned about a white dot on his right eye. Examination reveals a white pupillary reflex in his right eye. Imaging studies confirm the presence of a large tumor in the right eye that does not involve the optic nerve. It is diagnosed as the most common intraocular malignant tumor. What is the chromosomal abnormality that could be present in this case?

A- Deletion of a gene on the affected chromosome
B- Duplication of a gene on the affected chromosome
C- Missing of a chromosome
D- Presence of an extra chromosome
E- Replication of a chromosome

This is most likely a case of retinoblastoma. Familial cases of retinoblastoma are associated with deletion of Rb gene on chromosome 13. These patients are also at risk of developing osteosarcoma as well.
The correct answer is A

 

High-yield points from this set

  • Choking, coughing and cyanosis with the first feeds = tracheoesophageal fistula.
  • A child with bitemporal hemianopia and a calcified sellar mass = craniopharyngioma.
  • Webbed neck, lymphedema and widely spaced nipples = Turner syndrome; coarctation of the aorta is common.
  • Self-mutilation and high uric acid = Lesch-Nyhan syndrome (HGPRT deficiency).
  • Severe fasting hypoglycemia, lactic acidosis and hepatomegaly = von Gierke disease (glucose-6-phosphatase deficiency).
  • Bloody diarrhea followed by anemia with schistocytes, low platelets and kidney failure = HUS (Shiga toxin).
  • Phenotype = the observable traits produced by genotype plus environment.
  • Recurrent lung infections, poor growth and greasy stools = cystic fibrosis; sweat chloride test.
  • Premature breastfed infants need iron supplements.
  • White pupillary reflex (leukocoria) in an infant = retinoblastoma (RB1 gene deletion on chromosome 13).

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