Pediatric Dr. Ali

Question 1

A 10-year-old girl with known peanut allergy accidentally consumes a cookie containing peanuts at a school picnic. Within minutes, she develops hives on her face, wheezing, throat tightness, and difficulty breathing. Her oxygen saturation is 92% on room air, respiratory rate is 28/min, and she has visible swelling of lips and tongue.
Which of the following best explains the pharmacologic mechanism by which epinephrine treats this condition?

A) Epinephrine blocks histamine receptors, preventing mast cell mediators from causing bronchoconstriction
B) Epinephrine stimulates alpha-1 receptors causing vasoconstriction and beta-2 receptors causing bronchodilation
C) Epinephrine prevents further IgE-mediated mast cell degranulation by stabilizing cell membranes
D) Epinephrine primarily works through its anti-inflammatory effects on prostaglandin synthesis
E) Epinephrine antagonizes leukotrienes, the primary mediators of anaphylactic reactions

Answer 1

B

Question 2

A 15-year-old girl presents with an itchy, red, blistered rash on both earlobes that developed approximately 48 hours after wearing new inexpensive earrings. She has no systemic symptoms or other rashes elsewhere on her body.
Which of the following best characterizes the immunologic mechanism of this reaction?

A) Type I hypersensitivity with IgE-mediated mast cell degranulation
B) Type II hypersensitivity with antibody-dependent cytotoxicity
C) Type III hypersensitivity with immune complex deposition
D) Type IV hypersensitivity with T cell-mediated delayed reaction
E) Type V hypersensitivity with stimulating autoantibodies

Answer 2

D

Question 3

A 3-year-old boy presents with a history of 4 episodes of otitis media, 2 episodes of pneumonia, persistent skin candidiasis despite treatment, and ongoing sinus infections in the past year. His growth parameters are normal, and he has no significant family history of immune disorders.
Which of the following is the most appropriate initial diagnostic approach?
A) Immediate bone marrow biopsy to evaluate stem cell function
B) Quantitative immunoglobulin levels and lymphocyte subset analysis
C) Genetic testing for all known primary immunodeficiency mutations
D) Empiric treatment with broad-spectrum antibiotics and reassessment in 3 months
E) Skin testing for environmental allergies as the likely underlying cause

Answer 3

B

Question 4

A 12-year-old girl presents with several months of progressive fatigue, easy bruising, abdominal discomfort, early satiety, and intermittent bone pain in her lower back and hips. Physical examination reveals pallor, significant splenomegaly, and mild hepatomegaly. Her maternal grandfather had similar symptoms requiring hospitalization.
Which of the following is the most likely diagnosis?
A) Acute lymphoblastic leukemia
B) Gaucher disease
C) Niemann-Pick disease
D) Thalassemia major
E) Juvenile idiopathic arthritis with systemic features

Answer 4

B

Question 5

A 6-month-old girl presents with multiple respiratory tract infections, chronic diarrhea unresponsive to treatment, and poor weight gain despite adequate feeding. She is below the 3rd percentile for weight and height with delayed motor milestones. Laboratory results show markedly low lymphocyte count, absent T cells, very low B cells, and undetectable immunoglobulin levels.
What is the most definitive treatment for this condition?
A) Lifelong prophylactic antibiotics
B) Monthly intravenous immunoglobulin (IVIG) therapy
C) Hematopoietic stem cell transplantation
D) Enzyme replacement therapy
E) Thymus transplantation alone

Answer 5

C

Question 6

A 14-year-old boy, previously healthy and active in basketball, presents with progressive dull pain in the left lower thigh and swelling around the knee for two months. The pain is worse at night and unrelieved by rest or over-the-counter analgesics. X-ray reveals a mixed lytic and sclerotic lesion in the metaphyseal region of the distal femur with periosteal elevation (Codman triangle).
Which of the following is the most likely diagnosis?
A) Ewing sarcoma
B) Osteosarcoma
C) Osteomyelitis
D) Osteoid osteoma
E) Giant cell tumor

Answer 6

B

Question 7

An 8-year-old girl presents with fatigue, weight loss, and skin hyperpigmentation. She was recently diagnosed with autoimmune adrenalitis (Addison’s disease) and has a history of hypoparathyroidism. Her younger brother has Type 1 diabetes mellitus. Genetic testing reveals a mutation in the AIRE gene.
Which of the following best explains the pathophysiologic mechanism of her condition?
A) Defective peripheral tolerance with failure of regulatory T cells
B) Defective central tolerance with failure to eliminate self-reactive T cells in the thymus
C) Excessive production of autoantibodies by hyperactive B cells
D) Molecular mimicry between microbial antigens and self-antigens
E) Impaired clearance of immune complexes leading to tissue damage

Answer 7

B

Question 8

Two children with acute lymphoblastic leukemia (ALL) are compared: Sofia, a 5-year-old from Germany who receives prompt diagnosis and comprehensive treatment, and Deka, a 6-year-old from rural Somalia who experiences delayed diagnosis and limited therapeutic options.
Which factor most significantly contributes to the disparity in their expected outcomes?
A) Genetic differences in leukemia subtypes between European and African populations
B) Variations in nutritional status affecting chemotherapy metabolism
C) Access to timely diagnosis, specialized care, and supportive services
D) Differences in environmental exposures leading to more aggressive disease
E) Variations in immune system development affecting treatment response

Answer 8

C

Question 9

A 6-year-old boy presents with 5 days of mild nasal discharge, occasional dry cough, and low-grade fever (37.8°C). He continues to eat, drink, and play normally. Several children in his class have been absent with similar symptoms.
Which phase of pertussis infection does this presentation most likely represent?
A) Incubation phase
B) Catarrhal phase
C) Paroxysmal phase
D) Convalescent phase
E) Post-infectious phase

Answer 9

B

Question 10

A 5-year-old boy presents with frequent bruising and prolonged bleeding after minor injuries. His maternal uncle had a diagnosed bleeding disorder. Laboratory evaluation shows normal bleeding time, normal platelet count, normal prothrombin time (PT), prolonged activated partial thromboplastin time (aPTT), and normal fibrinogen level.
Which of the following is the most likely diagnosis?
A) Von Willebrand disease
B) Hemophilia A
C) Immune thrombocytopenic purpura
D) Vitamin K deficiency
E) Disseminated intravascular coagulation

Answer 10

B

Question 11

A 2-day-old term infant born to an Rh-negative mother who did not receive Rh immunoglobulin prophylaxis during pregnancy develops jaundice, pallor, lethargy, hepatosplenomegaly, and generalized edema. Laboratory findings include severe anemia, elevated indirect bilirubin, and a positive direct Coombs test.
Which of the following best explains the pathophysiology of this condition?
A) Congenital absence of bilirubin-conjugating enzymes
B) Maternal IgG antibodies crossing the placenta and destroying fetal Rh-positive erythrocytes
C) Congenital infection causing bone marrow suppression
D) Inherited red cell membrane defect leading to hemolysis
E) Excessive breakdown of fetal hemoglobin after birth

Answer 11

B

Question 12

A 9-month-old infant presents with chronic diarrhea, failure to thrive, and recurrent respiratory infections. Physical examination reveals oral thrush and generalized lymphadenopathy. Laboratory studies show low immunoglobulin levels and absent CD3+ T cells.
Which of the following is the most likely diagnosis?
A) Wiskott-Aldrich syndrome
B) Severe combined immunodeficiency (SCID)
C) X-linked agammaglobulinemia
D) Chronic granulomatous disease
E) Cystic fibrosis

Answer 12

C

Question 13

A 7-year-old boy presents with a 6-month history of recurrent abdominal pain, intermittent non-bloody diarrhea, and recent onset of swelling in his knees and ankles. Physical examination reveals growth failure, pallor, and tender joints with effusions. Laboratory studies show microcytic anemia, elevated ESR, and positive anti-tissue transglutaminase antibodies.
Which of the following is the most likely diagnosis?
A) Juvenile idiopathic arthritis
B) Inflammatory bowel disease
C) Celiac disease
D) Henoch-Schönlein purpura
E) Familial Mediterranean fever

Answer 13

C

Question 14

A 3-month-old previously healthy male infant presents with sudden onset of respiratory distress while feeding. He has tachypnea, intercostal retractions, and decreased breath sounds on the left side. Chest X-ray reveals a shift of the mediastinum to the right with a hyperinflated left hemithorax.
Which of the following is the most likely diagnosis?
A) Foreign body aspiration
B) Congenital lobar emphysema
C) Pneumothorax
D) Bronchiolitis
E) Congenital diaphragmatic hernia

Answer 14

C

Question 15

A 4-year-old girl presents with 24 hours of high fever (40°C), severe headache, vomiting, and neck stiffness. Physical examination reveals photophobia, positive Kernig’s and Brudzinski’s signs, and a petechial rash on her trunk and extremities. Her immunizations are up to date except for the meningococcal vaccine.
Which of the following is the most appropriate initial management?
A) Lumbar puncture after neuroimaging
B) Immediate administration of antibiotics followed by lumbar puncture
C) Antipyretics and observation for 24 hours
D) Antiviral therapy with acyclovir
E) Corticosteroids alone

Answer 15

B

Question 16

A 16-year-old girl presents with 3 months of progressive fatigue, 10 kg weight loss despite normal appetite, heat intolerance, difficulty sleeping, and tremors. Physical examination reveals tachycardia, mild exophthalmos, and a diffusely enlarged thyroid gland without nodules.
Which of the following laboratory findings would most likely confirm the diagnosis?
A) Elevated TSH, normal free T4
B) Low TSH, elevated free T4
C) Elevated TSH, low free T4
D) Normal TSH, elevated free T3 only
E) Low TSH, low free T4

Answer 16

B

Question 17

A 6-week-old male infant presents with progressively worsening non-bilious projectile vomiting after feeds. He is hungry after vomiting and eager to feed again. Physical examination reveals visible peristaltic waves across the upper abdomen and a palpable olive-shaped mass in the right upper quadrant.
Which of the following is the most appropriate next step in management?
A) Upper GI contrast study
B) Trial of thickened feeds and positioning
C) Surgical consultation for pyloromyotomy
D) Endoscopy to rule out esophageal stricture
E) Initiation of proton pump inhibitor therapy

Answer 17

C

Question 18

A 5-year-old boy presents with acute onset of right hip pain and refusal to bear weight. He has a low-grade fever (38.1°C) and appears otherwise well. Physical examination reveals limited and painful internal rotation of the right hip. Laboratory studies show mildly elevated white blood cell count and C-reactive protein.
Which of the following is the most likely diagnosis?
A) Septic arthritis
B) Transient synovitis
C) Legg-Calvé-Perthes disease
D) Slipped capital femoral epiphysis
E) Osteomyelitis

Answer 18

B

Question 19

A term newborn presents with ambiguous genitalia, including a small phallus, incomplete labioscrotal fusion, and a single urogenital opening. The infant appears otherwise healthy. Initial laboratory studies reveal elevated 17-hydroxyprogesterone levels.
Which of the following is the most likely diagnosis?
A) 5-alpha reductase deficiency
B) Androgen insensitivity syndrome
C) Congenital adrenal hyperplasia due to 21-hydroxylase deficiency
D) Turner syndrome
E) Mixed gonadal dysgenesis

Answer 19

C

Question 20

A 7-year-old boy presents with a 6-month history of recurrent epistaxis, easy bruising, and prolonged bleeding after minor injuries. Physical examination is unremarkable except for scattered petechiae on the lower extremities. Laboratory studies show normal hemoglobin, white blood cell count, and prolonged bleeding time with normal PT and PTT.
Which of the following is the most likely diagnosis?
A) Hemophilia A
B) Von Willebrand disease
C) Immune thrombocytopenic purpura
D) Bernard-Soulier syndrome
E) Factor VII deficiency

Answer 20

C

Question 21

A 9-month-old female infant presents with hypotonia, developmental delay, and failure to achieve age-appropriate motor milestones. She has almond-shaped eyes, a single palmar crease, and a protruding tongue. Cardiac evaluation reveals an atrioventricular septal defect.
Which of the following genetic abnormalities is most likely responsible for this presentation?
A) Trisomy 21
B) Trisomy 18
C) Trisomy 13
D) Turner syndrome (45,X)
E) Fragile X syndrome

Answer 21

A

Question 22

A 4-year-old boy presents with his third episode of pneumonia in the past year. He has a history of chronic productive cough, recurrent sinusitis, and failure to thrive despite a good appetite. Physical examination reveals digital clubbing and scattered crackles throughout both lung fields.
Which of the following tests would be most diagnostic?
A) Sweat chloride test
B) Tuberculin skin test
C) Alpha-1 antitrypsin level
D) HIV antibody test
E) Bronchoscopy with bronchoalveolar lavage

Answer 22

A

Question 23

A 15-year-old boy presents with sudden onset of severe left testicular pain and swelling for 2 hours. He denies trauma, fever, or urinary symptoms. Physical examination reveals a high-riding, tender left testicle with an absent cremasteric reflex.
Which of the following is the most appropriate next step in management?
A) Urinalysis and urine culture
B) Color Doppler ultrasound of the scrotum
C) Immediate surgical exploration
D) Trial of analgesics and elevation
E) Antibiotics for presumed epididymitis

Answer 23

C

Question 24

A previously healthy 3-year-old girl presents with acute onset of ataxia, nystagmus, and slurred speech following a viral illness 2 weeks ago. She has no fever, headache, or altered mental status. Neurological examination confirms cerebellar signs without focal deficits.
Which of the following is the most likely diagnosis?
A) Brain tumor
B) Acute cerebellar ataxia
C) Guillain-Barré syndrome
D) Acute disseminated encephalomyelitis
E) Toxic ingestion

Answer 24

B

Question 25

A 2-day-old term male infant presents with bilious vomiting, abdominal distension, and failure to pass meconium. Abdominal X-ray shows dilated loops of bowel with air-fluid levels. Contrast enema reveals a microcolon with a transition zone. Which of the following is the most likely diagnosis? A) Pyloric stenosis B) Duodenal atresia C) Malrotation with volvulus D) Hirschsprung disease E) Meconium ileus

Answer 25

D

Question 26

A 10-year-old girl with a known peanut allergy accidentally eats a peanut-containing cookie during a school picnic. Within minutes, she develops hives on her face, wheezing, throat tightness, and difficulty breathing. She has an epinephrine auto-injector but has never used it. Her respiratory rate is 28/min, oxygen saturation is 92% on room air, and she has lip and tongue swelling. What is the next best step in management? A) Administer diphenhydramine and observe B) Provide high-flow oxygen and wait for hypotension to develop C) Administer intramuscular epinephrine immediately D) Start intravenous corticosteroids

Answer 26

C

Question 27

A 15-year-old girl presents with an itchy, red, blistered rash on both earlobes two days after wearing new inexpensive earrings. She has no fever or systemic symptoms. On examination, she has vesicular, erythematous lesions on the earlobes. Which of the following best describes the immunologic mechanism involved? A) Type I hypersensitivity mediated by IgE B) Type II hypersensitivity with antibody-dependent cytotoxicity C) Type III immune complex deposition D) Type IV delayed-type hypersensitivity mediated by T-cells

Answer 27

D

Question 28

A 6-month-old girl has had recurrent respiratory infections, chronic diarrhea, and poor weight gain despite adequate feeding. Examination shows failure to thrive, absent tonsils, and mild respiratory distress. Laboratory evaluation reveals very low lymphocyte counts, absent T cells, and undetectable immunoglobulin levels. What is the most likely diagnosis? A) Wiskott-Aldrich syndrome B) Severe Combined Immunodeficiency (SCID) C) Chronic granulomatous disease D) DiGeorge syndrome

Answer 28

B; SCID involves profound T and B cell deficiency, leading to severe infections and failure to thrive.

Question 29

A 14-year-old previously healthy boy has 2 months of progressive pain and swelling around his left knee, worse at night, and not relieved by rest or NSAIDs. Examination shows localized swelling and tenderness over the distal femur without joint effusion. X-ray shows a mixed lytic-sclerotic lesion with periosteal elevation (Codman triangle). Biopsy confirms a malignant bone tumor. What is the most likely diagnosis? A) Ewing sarcoma B) Osteosarcoma C) Chondrosarcom

Answer 29

B

Question 30

An 8-year-old girl presents with fatigue, weight loss, and skin hyperpigmentation. She was diagnosed with Addison’s disease, and also has hypoparathyroidism. Her brother has type 1 diabetes. Laboratory testing shows high ACTH, low cortisol, and positive anti-adrenal antibodies. Genetic testing finds a mutation in the AIRE gene. Which of the following best explains the pathogenesis of her condition? A) Failure of negative selection in the thymus B) Deficiency of complement proteins C) IgA deficiency leading to mucosal autoimmunity D) Impaired B cell receptor editing

Answer 30

A

Question 31

A 5-year-old girl in a high-income country is diagnosed with acute lymphoblastic leukemia (ALL) and begins chemotherapy soon after. Another 6-year-old girl in a low-income country presents with the same symptoms but is misdiagnosed twice, delaying treatment. What is the most important factor contributing to the difference in outcomes between these two patients? A) Differences in leukemia subtypes B) Variation in parental education C) Access to timely diagnosis and specialized care D) Differences in environmental exposures

Answer 31

C

Question 32

A 2-day-old term newborn has jaundice, pallor, lethargy, and hepatosplenomegaly. He was born to an Rh-negative mother who did not receive Rh immunoglobulin prophylaxis. Labs show severe anemia, elevated indirect bilirubin, and a positive direct Coombs test. What is the most likely diagnosis? A) Physiologic jaundice of the newborn B) ABO incompatibility C) Rh hemolytic disease of the newborn D) G6PD deficiency

Answer 32

C; Rh incompatibility can cause severe hemolysis, anemia, jaundice, and hydrops fetalis if untreated.

Question 33

A 6-month-old infant has persistent productive cough, poor weight gain despite feeding, and frequent foul-smelling bulky stools. On exam, there is mild digital clubbing. Sweat chloride test is elevated. Which of the following best describes the underlying pathophysiology? A) Abnormal ciliary motility B) Deficiency of alpha-1 antitrypsin C) Defective chloride channels D) Immunoglobulin deficiency

Answer 33

C; Cystic fibrosis is caused by defective CFTR chloride channels leading to thick mucus and organ dysfunction.

Question 34

A premature male infant born at 28 weeks develops respiratory distress shortly after birth, with tachypnea, nasal flaring, and grunting. Chest X-ray shows diffuse ground-glass opacities and air bronchograms. What is the most likely cause? A) Pulmonary hypoplasia B) Bronchopulmonary dysplasia C) Surfactant deficiency D) Congenital diaphragmatic hernia

Answer 34

C: Neonatal RDS results from inadequate surfactant production by immature type II pneumocytes in preterm infants

Question 35

A medical student asks about a fetal vessel that allows blood to bypass the pulmonary circulation by connecting the pulmonary artery to the aorta. Which of the following structures serves this function? A) Foramen ovale B) Ductus venosus C) Ductus arteriosus D) Sinus venosus

Answer 35

C; The ductus areriosus connects the pulmonary artery to the aorta, allowing right-to-left shunting before birth.

Question 36

A 10-year-old girl has abdominal pain, bloating, weight loss, intermittent fever, and night sweats for several weeks. On exam, there are palpable mesenteric lymph nodes but no hepatosplenomegaly. Which of the following is the most likely diagnosis? A) Wilms tumor B) Non-Hodgkin lymphoma C) Neuroblastoma D) Ovarian teratoma

Answer 36

B

Question 37

A 7-year-old boy has fatigue, pallor, frequent nosebleeds, and easy bruising over the past few weeks. Examination shows multiple petechiae, hepatosplenomegaly, and pallor. There is no significant family history. Which of the following is the most likely diagnosis? A) Immune thrombocytopenic purpura B) Acute lymphoblastic leukemia C) Aplastic anemia D) von Willebrand disease

Answer 37

B

Question 38

A 6-month-old girl is brought in for poor feeding, irritability, and delayed milestones. Parents notice a “mousy” odor from her sweat and urine. She has fair skin and hair, despite dark-skinned parents. Blood testing shows elevated phenylalanine. What is the best next step in management? A) Start a diet low in phenylalanine B) Begin vitamin B12 supplementation C) Give oral iron D) Reassure parents that this will resolve

Answer 38

A

Question 39

A 6-year-old boy has 3 weeks of early morning vomiting and clumsiness while walking. Exam reveals truncal ataxia and dysmetria. MRI shows a midline cerebellar mass with hydrocephalus. Biopsy shows small round blue cells forming Homer Wright pseudorosettes. What is the most likely diagnosis? A) Pilocytic astrocytoma B) Ependymoma C) Medulloblastoma D) Craniopharyngioma

Answer 39

C

Question 40

A 5-year-old boy with 2 days of vomiting and watery diarrhea has lethargy, decreased urine output, dry mucous membranes, and delayed capillary refill. Labs show elevated BUN/creatinine ratio and mild hypokalemia. What is the most likely cause of his kidney injury? A) Acute tubular necrosis B) Post-streptococcal glomerulonephritis C) Prerenal azotemia D) Hemolytic uremic syndrome

Answer 40

C

Question 41

An 11-year-old girl with known Henoch-Schönlein purpura nephritis has fatigue, poor appetite, leg swelling, and decreased urine output. Blood pressure is elevated, and labs show eGFR 18 mL/min/1.73m² with persistent proteinuria. What stage of chronic kidney disease does she currently have? A) Stage 2 B) Stage 3a C) Stage 4 D) Stage 5

Answer 41

C;

Question 42

A 7-year-old girl has had 4 relapses of nephrotic syndrome in the past year, each following upper respiratory infections. She presents again with facial swelling and ascites. Lab tests show heavy proteinuria, low serum albumin, and normal renal function. Kidney biopsy shows normal glomeruli on light microscopy, no immune deposits on immunofluorescence, and diffuse podocyte foot process effacement on EM. What is the most likely diagnosis? A) Focal segmental glomerulosclerosis B) Membranous nephropathy C) Minimal change disease D) Membranoproliferative GN

Answer 42

C

Question 43

A 3-year-old boy has poor appetite, weight loss, and a firm right-sided abdominal mass. Imaging confirms a retroperitoneal adrenal mass, with elevated urinary vanillylmandelic acid and bone marrow metastasis. Genetic testing reveals MYCN amplification. What is the most likely diagnosis? A) Wilms tumor B) Neuroblastoma C) Hepatoblastoma D) Rhabdomyosarcoma

Answer 43

B

Question 44

A 2-year-old boy with a history of aniridia, hypospadias, and developmental delay is found to have a painless, firm left-sided flank mass on routine exam. Abdominal imaging shows a renal mass; genetic testing finds a deletion on chromosome 11p13. What is the most likely diagnosis? A) Neuroblastoma B) Renal cell carcinoma C) Wilms tumor associated with WAGR syndrome D) Hepatoblastoma

Answer 44

C

Question 45

A 4-week-old infant has persistent jaundice, poor feeding, irritability, and a petechial rash. The mother had a febrile rash illness during the second trimester. Exam reveals hepatosplenomegaly and periventricular calcifications on head ultrasound. Which of the following pathogens is most likely responsible? A) Herpes simplex virus B) Rubella virus C) Toxoplasma gondii D) Cytomegalovirus

Answer 45

D

Question 46

A 2-year-old boy has had an itchy, dry, red rash on both cheeks since infancy, worse with cold weather and soaps. He often wakes at night scratching. Exam shows erythematous, lichenified plaques on the cheeks and dry skin on the trunk. There is a family history of asthma. What is the most appropriate first-line management? A) Daily systemic corticosteroids B) Daily emollients with low-potency topical corticosteroids C) High-potency topical steroids D) Oral antibiotics

Answer 46

B

Question 47

A 7-year-old girl develops sudden lip and cheek swelling a few hours after a minor dental procedure. She denies itching, pain, or breathing difficulty. Her mother recalls a similar episode with abdominal pain in the past. On exam, there is non-pruritic, non-pitting facial swelling without rash. Which of the following is the most likely underlying mechanism? A) IgE-mediated mast cell degranulation B) Complement C1 esterase inhibitor deficiency C) Type II antibody-mediated cytotoxic reaction D) Type IV T-cell mediated delayed hypersensitivity

Answer 47

B

Question 48

A 7-year-old girl is brought in for a painless, firm, enlarging mass on her left upper arm that developed over 3 weeks. There is no fever, trauma, or systemic symptoms. MRI shows a soft tissue mass, and biopsy reveals small round blue cells of mesenchymal origin. What is the most likely diagnosis? A) Osteosarcoma B) Ewing sarcoma C) Embryonal rhabdomyosarcoma D) Neuroblastoma

Answer 48

C