An 11-month-old boy is brought to a pediatrician by his parents for evaluation of vomiting and watery diarrhea over the last day. The mother informs the pediatrician that the boy had consumed an apple bought from a fruit vendor on the previous day, but that otherwise there has been no recent change in his diet. There is no history of blood in the stool, flatulence, irritability, or poor appetite. There is no history of recurrent or chronic diarrhea or any other gastrointestinal symptoms. On physical examination, his temperature is 37.6°C (99.6°F), pulse is 120/min, respirations are 24/min, and blood pressure is 92/60 mm Hg. General examination reveals a playful infant with normal skin turgor and no sunken eyes. The pediatrician explains to the parents that he most likely has acute gastroenteritis and that no specific medication is indicated at present. He also instructs the parents about his diet during the illness and reviews the danger signs of dehydration. He suggests a follow-up evaluation after 48 hours or earlier if any complications arise. Which of the following dietary recommendations did the pediatrician make?
Q172
A 28-year-old gravida 1 para 1 woman is being seen in the hospital for breast tenderness. She reports that both breasts are swollen and tender. She is also having difficulty getting her newborn to latch. The patient gave birth 4 days ago by uncomplicated vaginal delivery. During her pregnancy, the patient developed gestational diabetes but was otherwise healthy. She took folate and insulin. She attended all her pre-natal appointments. Upon examination, the patient has a low grade fever, but all other vital signs are stable. Bilateral breasts appear engorged and are tender to palpation. There is no erythema, warmth, or induration. A lactation nurse is brought in to assist the patient and her newborn with more effective breastfeeding positions. The patient says a neighbor told her that breastmilk actually lacks in nutrients, and she asks what the best option is for the health of her newborn. Which of the following components is breastmilk a poor source of?
Q173
A clinical study is studying new genetic gene-based therapies for children and adults with sickle cell disease. The patients were informed that they were divided into two age groups since younger patients suffer from different complications of the disease. The pediatric group is more likely to suffer from which of the complications?
I. Splenic sequestration
II. Avascular necrosis
III. Pulmonary hypertension
IV. Acute chest syndrome
V. Nephropathy
Q174
A 4-month-old girl is brought to the physician because she has been regurgitating and vomiting 10–15 minutes after feeding for the past 3 weeks. She is breastfed and formula-fed. She was born at 38 weeks' gestation and weighed 2966 g (6 lb 9 oz). She currently weighs 5878 g (12 lb 15 oz). She appears healthy. Vital signs are within normal limits. Examination shows a soft and nontender abdomen and no organomegaly. Which of the following is the most appropriate next best step in management?
Q175
A 2-year-old boy is brought to the emergency department by his mother because of progressive fatigue, abdominal pain, and loss of appetite over the past 3 days. He was treated in the emergency department once in the past year for swelling of his hands and feet. He was adopted as a baby from Sudan and his family history is unknown. He does not take any medication. He is lethargic. His temperature is 37.5°C (99.5°F), pulse is 141/min, respirations are 25/min, and blood pressure is 68/40 mm Hg. Examination shows pale, dry mucous membranes and scleral icterus. Laboratory studies show:
Hemoglobin 7.1 g/dL
Mean corpuscular volume 93 fL
Reticulocyte count 11%
Serum
Lactate dehydrogenase 194 IU/L
Total bilirubin 6.4 mg/dL
Direct bilirubin 0.5 mg/dL
Haptoglobin 21 mg/dL (N = 41–165)
Further evaluation of this patient is most likely to show which of the following findings?
Q176
A 3-month-old boy is brought to the physician by his parents for the evaluation of a rash on his scalp and forehead. The parents report that the rash has been present for several weeks. They state that the rash is sometimes red and scaly, especially when it is cold. The patient was born at 36 weeks' gestation and has generally been healthy since. His father has psoriasis. The patient appears comfortable. Examination shows several erythematous patches on the scalp, forehead, and along the hairline. Some patches are covered by greasy yellow scales. Which of the following is the most likely diagnosis?
Q177
A 1-month-old boy is brought in by his mother for episodes of “not breathing.” She reports noticing that the patient will occasionally stop breathing while he’s sleeping, and that these episodes have been occurring more frequently. The patient was born at 32 weeks due to placental insufficiency. He was in the neonatal intensive care unit for 1 day to be placed on a respirator. During prenatal testing, it was revealed that the mother was not immune to rubella, but she otherwise had an uncomplicated pregnancy. She has no medical conditions and took only prenatal vitamins. The patient has a 3-year-old sister who is healthy. His father has a “heart condition.” The patient’s temperature is 98°F (36.7°C), blood pressure is 91/55 mmHg, pulse is 207/min, and respirations are 50/min with an oxygen saturation of 97% on room air. Physical examination is notable for pale conjunctiva. Labs are obtained, as shown below:
Leukocyte count: 10,000/mm^3 with normal differential
Hemoglobin: 8.2 g/dL
Hematocrit: 28%
Mean corpuscular volume (MCV): 100 um^3
Platelet count: 300,000/mm^3
Reticulocyte count: 0.8% (normal range: 2-6%)
Lactate dehydrogenase: 120 U/L (normal range: 100-250 U/L)
A peripheral smear reveals normocytic and normochromic red blood cells. Which of the following is a mechanism for the patient’s most likely diagnosis?
Q178
An 11-month-old boy presents with the recent loss of appetite and inability to gain weight. His diet consists mainly of cow’s milk and fruits. Family history is unremarkable. Physical examination shows conjunctival pallor. Laboratory findings are significant for the following:
Hemoglobin 9.1 g/dL
Mean corpuscular volume 75 μm3
Mean corpuscular hemoglobin 20 pg/cell
Red cell distribution width 18%
The patient is presumptively diagnosed with iron deficiency anemia (IDA) and ferrous sulfate syrup is prescribed. Which of the following laboratory values would most likely change 1st in response to this treatment?
Q179
A 10-month-old infant is brought in by his parents because he is vomiting and not passing stool. His parents say he has vomited multiple times over the past couple of hours, but the most recent vomit was green. The patient has no significant past medical history. On physical examination, the patient is irritable and crying. On palpation in the periumbilical region, an abdominal mass is present. Emergency laparotomy is performed, which shows a part of the patient’s intestine folded into the section adjacent to it. Which of the following is the most likely diagnosis for this patient?
Q180
A 3-year-old boy is brought to the physician by his mother for the evaluation of delay in attaining developmental milestones. He could sit upright by 14 months and has not been able to walk without support. He can build a tower of 3 blocks and cannot use utensils to feed himself. He speaks in unclear 2-word phrases and cannot draw a circle yet. His mother has noticed him hitting his head against the wall on multiple occasions. He is at 20th percentile for height and at 50th percentile for weight. Vitals signs are within normal limits. Examination shows multiple lacerations of his lips and tongue. There are multiple healing wounds over his fingers. Neurological examination shows increased muscle tone in all extremities. Laboratory studies show:
Hemoglobin 10.1 g/dL
Mean corpuscular volume 103 μm3
Serum
Na+ 142 mEq/L
Cl- 101 mEq/:
K+ 4.1 mEq/L
Creatinine 1.6 mg/dL
Uric acid 12.3 mg/dL
Which of the following is the most likely cause of this patient's findings?
Growth/Development US Medical PG Practice Questions and MCQs
Question 171: An 11-month-old boy is brought to a pediatrician by his parents for evaluation of vomiting and watery diarrhea over the last day. The mother informs the pediatrician that the boy had consumed an apple bought from a fruit vendor on the previous day, but that otherwise there has been no recent change in his diet. There is no history of blood in the stool, flatulence, irritability, or poor appetite. There is no history of recurrent or chronic diarrhea or any other gastrointestinal symptoms. On physical examination, his temperature is 37.6°C (99.6°F), pulse is 120/min, respirations are 24/min, and blood pressure is 92/60 mm Hg. General examination reveals a playful infant with normal skin turgor and no sunken eyes. The pediatrician explains to the parents that he most likely has acute gastroenteritis and that no specific medication is indicated at present. He also instructs the parents about his diet during the illness and reviews the danger signs of dehydration. He suggests a follow-up evaluation after 48 hours or earlier if any complications arise. Which of the following dietary recommendations did the pediatrician make?
A. Plenty of juices and carbonated sodas
B. Age-appropriate diet (Correct Answer)
C. Diluted formula milk
D. Lactose-free diet
E. BRAT diet
Explanation: ***Age-appropriate diet***
- For **mild acute gastroenteritis** without significant dehydration, the latest recommendations advise continuing **age-appropriate feeding** to support nutritional requirements and promote gut recovery.
- This approach helps to prevent malnutrition and does not prolong the course of diarrhea.
*Plenty of juices and carbonated sodas*
- **High sugar content** in juices and sodas can worsen diarrhea due to their **osmotic effect**, drawing more water into the intestine.
- These beverages also lack essential **electrolytes** needed for rehydration.
*Diluted formula milk*
- Diluting formula can lead to **insufficient caloric intake** and nutritional deficiencies, which is generally not recommended for mild gastroenteritis.
- Undiluted formula is usually well-tolerated, as most infants with acute gastroenteritis do not develop significant **lactose intolerance**.
*Lactose-free diet*
- Routine use of **lactose-free diets** is generally not recommended unless there is strong evidence of **secondary lactase deficiency**, which typically presents with increased flatulence, bloating, and worsening diarrhea.
- The majority of children with acute gastroenteritis can tolerate their usual milk intake.
*BRAT diet*
- The **B**ananas, **R**ice, **A**pplesauce, **T**oast (BRAT) diet is **nutritionally restrictive**, providing inadequate protein and fat, which can hinder recovery and growth in infants.
- Current guidelines no longer recommend the BRAT diet for acute gastroenteritis.
Question 172: A 28-year-old gravida 1 para 1 woman is being seen in the hospital for breast tenderness. She reports that both breasts are swollen and tender. She is also having difficulty getting her newborn to latch. The patient gave birth 4 days ago by uncomplicated vaginal delivery. During her pregnancy, the patient developed gestational diabetes but was otherwise healthy. She took folate and insulin. She attended all her pre-natal appointments. Upon examination, the patient has a low grade fever, but all other vital signs are stable. Bilateral breasts appear engorged and are tender to palpation. There is no erythema, warmth, or induration. A lactation nurse is brought in to assist the patient and her newborn with more effective breastfeeding positions. The patient says a neighbor told her that breastmilk actually lacks in nutrients, and she asks what the best option is for the health of her newborn. Which of the following components is breastmilk a poor source of?
A. Whey protein
B. Vitamin D (Correct Answer)
C. Lysozymes
D. Phosphorus
E. Immunoglobulin A
Explanation: ***Vitamin D***
- **Breast milk** is naturally a **poor source of vitamin D**, making supplementation necessary for breastfed infants to prevent **rickets** and ensure adequate bone development.
- While small amounts of vitamin D are present, they are often insufficient to meet the infant's requirements, especially if maternal vitamin D levels are also low.
*Whey protein*
- **Whey protein** is a major component of breast milk, contributing to its digestibility and providing essential **amino acids** for infant growth.
- It is specifically rich in **alpha-lactalbumin**, which has both nutritional and antimicrobial properties.
*Lysozymes*
- **Lysozymes** are abundant in breast milk and play a crucial role in the infant's innate **immune defense** by breaking down bacterial cell walls.
- These enzymes help protect against gastrointestinal infections and contribute to the establishment of healthy gut flora.
*Phosphorus*
- **Phosphorus** is an essential mineral found in sufficient quantities in **breast milk**, crucial for **bone mineralization**, energy metabolism, and cell function.
- Its concentration is carefully regulated to meet the needs of the growing infant without overloading immature kidneys.
*Immunoglobulin A*
- **Secretory IgA (sIgA)** is the predominant **immunoglobulin** in breast milk, providing passive immunity by coating the infant's intestinal tract and preventing pathogen attachment.
- It is crucial for protecting the infant from various infections, especially those affecting the gastrointestinal and respiratory systems.
Question 173: A clinical study is studying new genetic gene-based therapies for children and adults with sickle cell disease. The patients were informed that they were divided into two age groups since younger patients suffer from different complications of the disease. The pediatric group is more likely to suffer from which of the complications?
I. Splenic sequestration
II. Avascular necrosis
III. Pulmonary hypertension
IV. Acute chest syndrome
V. Nephropathy
A. III, IV
B. I, II
C. I, II, IV
D. I, IV (Correct Answer)
E. I, IV, V
Explanation: ***I, IV***
- **Splenic sequestration crisis** is common in infants and young children with sickle cell disease because the spleen is still functional and can acutely pool red blood cells, leading to severe anemia and hypovolemic shock.
- **Acute chest syndrome** occurs across all ages but is particularly prevalent in pediatric patients, often triggered by infection or vaso-occlusion in the pulmonary vasculature.
*III, IV*
- While acute chest syndrome (IV) is common in children, **pulmonary hypertension** (III) is typically a complication that develops over decades in adults with sickle cell disease, due to chronic pulmonary vascular damage.
- This option incorrectly groups a chronic adult complication with an acute pediatric one, overlooking other more prevalent pediatric issues.
*I, II*
- **Splenic sequestration** (I) is indeed a pediatric complication, but **avascular necrosis** (II) usually develops over time, making it more common in adolescents and adults due to repetitive micro-infarctions in bone.
- This option misses acute chest syndrome, a highly significant and frequent pediatric complication.
*I, II, IV*
- While Splenic sequestration (I) and Acute Chest Syndrome (IV) are common in pediatric patients, **avascular necrosis** (II) is typically seen in older children, adolescents, and adults.
- Including avascular necrosis makes this option less accurate for *younger* pediatric groups, where acute complications dominate.
*I, IV, V*
- **Splenic sequestration** (I) and **Acute Chest Syndrome** (IV) are indeed pediatric complications, but **nephropathy** (V), including chronic kidney disease and proteinuria, generally develops later in life due to chronic renal ischemia and damage.
- This option incorrectly includes a chronic adult complication as a primary pediatric issue.
Question 174: A 4-month-old girl is brought to the physician because she has been regurgitating and vomiting 10–15 minutes after feeding for the past 3 weeks. She is breastfed and formula-fed. She was born at 38 weeks' gestation and weighed 2966 g (6 lb 9 oz). She currently weighs 5878 g (12 lb 15 oz). She appears healthy. Vital signs are within normal limits. Examination shows a soft and nontender abdomen and no organomegaly. Which of the following is the most appropriate next best step in management?
A. Upper endoscopy
B. Ultrasound of the abdomen
C. Esophageal pH monitoring
D. Positioning therapy (Correct Answer)
E. Pantoprazole therapy
Explanation: ***Positioning therapy***
- This infant is thriving, as evidenced by her significant weight gain, despite her regurgitation and vomiting. Her examination is also benign. These features make **gastroesophageal reflux (GER)**, a physiological process, the most likely diagnosis.
- **Positioning therapy** (e.g., keeping the infant upright during and after feeds) is a first-line, conservative management strategy for GER in infants who are otherwise healthy and gaining weight well.
*Upper endoscopy*
- **Upper endoscopy** is an invasive procedure and is typically reserved for evaluating patients with suspected complicated gastroesophageal reflux disease (GERD), such as those with **poor weight gain**, **hematemesis**, or **esophagitis**, none of which are seen here.
- It would not be the initial step in a thriving infant with symptoms consistent with uncomplicated GER.
*Ultrasound of the abdomen*
- An **abdominal ultrasound** is primarily used to diagnose **pyloric stenosis** in infants, which typically presents with **projectile, non-bilious vomiting** and **poor weight gain** or weight loss, usually between 3 and 6 weeks of age.
- This infant's symptoms are different in character (regurgitation/vomiting 10-15 minutes after feeding, not projectile) and she is gaining weight well, making pyloric stenosis less likely.
*Esophageal pH monitoring*
- **Esophageal pH monitoring** is used to quantify acid reflux episodes and is typically reserved for infants with atypical symptoms, suspected **complicated GERD**, or those who have failed empirical therapy.
- It is not indicated as a primary diagnostic or management step in a healthy, thriving infant with typical GER symptoms.
*Pantoprazole therapy*
- **Proton pump inhibitors (PPIs)** like pantoprazole are used to treat **GERD** by reducing stomach acid production, especially in cases with evidence of **esophagitis** or significant symptoms impacting growth or comfort.
- Given this infant is thriving and has no signs of complications, acid-suppressing medication is not appropriate as the initial management step; conservative measures should be tried first.
Question 175: A 2-year-old boy is brought to the emergency department by his mother because of progressive fatigue, abdominal pain, and loss of appetite over the past 3 days. He was treated in the emergency department once in the past year for swelling of his hands and feet. He was adopted as a baby from Sudan and his family history is unknown. He does not take any medication. He is lethargic. His temperature is 37.5°C (99.5°F), pulse is 141/min, respirations are 25/min, and blood pressure is 68/40 mm Hg. Examination shows pale, dry mucous membranes and scleral icterus. Laboratory studies show:
Hemoglobin 7.1 g/dL
Mean corpuscular volume 93 fL
Reticulocyte count 11%
Serum
Lactate dehydrogenase 194 IU/L
Total bilirubin 6.4 mg/dL
Direct bilirubin 0.5 mg/dL
Haptoglobin 21 mg/dL (N = 41–165)
Further evaluation of this patient is most likely to show which of the following findings?
A. Splenomegaly on ultrasound (Correct Answer)
B. Low ferritin level in serum
C. Hypocellular bone marrow on biopsy
D. Anti-erythrocyte antibodies on Coombs test
E. Pale stool on rectal examination
Explanation: ***Splenomegaly on ultrasound***
- The clinical picture of **anemia** (Hb 7.1 g/dL), **jaundice** (scleral icterus, total bilirubin 6.4 mg/dL with indirect predominance), **elevated LDH**, and **low haptoglobin** points to **hemolytic anemia**. The high reticulocyte count (11%) indicates a robust bone marrow response to red blood cell destruction.
- The history of **swelling of hands and feet** in a 2-year-old child from **Sudan** is highly suggestive of **sickle cell disease** (dactylitis is an early manifestation). In sickle cell disease, the **spleen** is often enlarged due to **red blood cell sequestration** and chronic hemolysis, especially in childhood, before repeated infarctions lead to autosplenectomy.
*Low ferritin level in serum*
- **Ferritin** is an **acute phase reactant** and a measure of **iron stores**. In chronic hemolytic conditions like sickle cell disease, patients often experience **iron overload** due to repeated transfusions or increased absorption from chronic red cell turnover.
- Therefore, a **low ferritin level** is unlikely in this scenario; **elevated ferritin** is more probable.
*Hypocellular bone marrow on biopsy*
- The **reticulocyte count is 11%**, which is **markedly elevated**. This indicates a **hypercellular bone marrow** that is actively producing red blood cells to compensate for the ongoing hemolysis.
- **Hypocellular bone marrow** would be seen in conditions like aplastic anemia, which is characterized by **pancytopenia** and a **low reticulocyte count**.
*Anti-erythrocyte antibodies on Coombs test*
- The symptoms are consistent with **sickle cell disease**, a **non-immune hemolytic anemia**.
- **Anti-erythrocyte antibodies** are found in **autoimmune hemolytic anemia**, where the Coombs test would be positive. This is not suggested by the patient's presentation.
*Pale stool on rectal examination*
- **Pale stools** (acholic stools) are indicative of **biliary obstruction** or **cholestasis**, where bilirubin is prevented from reaching the intestines and being converted to urobilinogen, which gives stool its brown color.
- This patient has **indirect hyperbilirubinemia**, which suggests **increased bilirubin production** from hemolysis, not impaired excretion into the bile duct. **Scleral icterus** is also consistent with hemolysis.
Question 176: A 3-month-old boy is brought to the physician by his parents for the evaluation of a rash on his scalp and forehead. The parents report that the rash has been present for several weeks. They state that the rash is sometimes red and scaly, especially when it is cold. The patient was born at 36 weeks' gestation and has generally been healthy since. His father has psoriasis. The patient appears comfortable. Examination shows several erythematous patches on the scalp, forehead, and along the hairline. Some patches are covered by greasy yellow scales. Which of the following is the most likely diagnosis?
A. Erythroderma
B. Atopic dermatitis
C. Seborrheic dermatitis (Correct Answer)
D. Allergic contact dermatitis
E. Seborrheic keratosis
Explanation: ***Seborrheic dermatitis***
- The presentation of **erythematous patches** with **greasy yellow scales** on the scalp and face in an infant is characteristic of **cradle cap**, which is infantile seborrheic dermatitis.
- The involvement of the **forehead** and **hairline** further supports this diagnosis, as these are common areas for seborrheic dermatitis in infants.
*Erythroderma*
- **Erythroderma** (exfoliative dermatitis) is characterized by generalized redness and scaling affecting more than **90% of the body surface area**.
- This patient's rash is localized to the scalp and face, which is inconsistent with the diffuse nature of erythroderma.
*Atopic dermatitis*
- **Atopic dermatitis** typically presents with intensely **pruritic** (itchy) eczematous lesions, which are often dry and red.
- While it can affect the face and scalp in infants, the description of **greasy yellow scales** is more characteristic of seborrheic dermatitis, and **pruritus** is not highlighted as a prominent symptom.
*Allergic contact dermatitis*
- **Allergic contact dermatitis** results from an immune reaction to contact with an allergen, often presenting with **intensely pruritic**, well-demarcated eczematous lesions, sometimes with **vesicles** or **bullae**.
- There is no mention of exposure to a new product or an itchy rash in this case, and the appearance with greasy scales is not typical.
*Seborrheic keratosis*
- **Seborrheic keratoses** are benign epidermal tumors that typically appear as **waxy, 'stuck-on' lesions**, usually in older adults, and are rarely seen in infants.
- The description of **erythematous patches** with **greasy scales** in an infant does not fit the characteristics of seborrheic keratoses.
Question 177: A 1-month-old boy is brought in by his mother for episodes of “not breathing.” She reports noticing that the patient will occasionally stop breathing while he’s sleeping, and that these episodes have been occurring more frequently. The patient was born at 32 weeks due to placental insufficiency. He was in the neonatal intensive care unit for 1 day to be placed on a respirator. During prenatal testing, it was revealed that the mother was not immune to rubella, but she otherwise had an uncomplicated pregnancy. She has no medical conditions and took only prenatal vitamins. The patient has a 3-year-old sister who is healthy. His father has a “heart condition.” The patient’s temperature is 98°F (36.7°C), blood pressure is 91/55 mmHg, pulse is 207/min, and respirations are 50/min with an oxygen saturation of 97% on room air. Physical examination is notable for pale conjunctiva. Labs are obtained, as shown below:
Leukocyte count: 10,000/mm^3 with normal differential
Hemoglobin: 8.2 g/dL
Hematocrit: 28%
Mean corpuscular volume (MCV): 100 um^3
Platelet count: 300,000/mm^3
Reticulocyte count: 0.8% (normal range: 2-6%)
Lactate dehydrogenase: 120 U/L (normal range: 100-250 U/L)
A peripheral smear reveals normocytic and normochromic red blood cells. Which of the following is a mechanism for the patient’s most likely diagnosis?
A. Red blood cell membrane defect
B. Minor blood group incompatibility
C. Hemoglobinopathy
D. Impaired erythropoietin production (Correct Answer)
E. Congenital infection
Explanation: ***Impaired erythropoietin production***
- This patient presents with **anemia of prematurity**, indicated by **normocytic, normochromic anemia** with a **low reticulocyte count** in a premature infant.
- The primary mechanism for **anemia of prematurity** is a blunted erythropoietin response to early anemia, leading to **impaired red blood cell production**.
*Red blood cell membrane defect*
- Conditions like **hereditary spherocytosis** or **elliptocytosis** involve red blood cell membrane defects, which typically lead to **hemolytic anemia** with elevated reticulocyte count.
- The patient's **low reticulocyte count** and normal LDH (lactate dehydrogenase is a marker of hemolysis) make a primary membrane defect less likely.
*Minor blood group incompatibility*
- **Minor blood group incompatibilities** (e.g., ABO, Kell, Duffy) typically cause **hemolytic disease of the newborn**, characterized by **elevated reticulocyte count**, **hyperbilirubinemia**, and signs of hemolysis.
- The patient exhibits no signs of hemolysis, such as elevated bilirubin or LDH, and has a normal reticulocyte count.
*Hemoglobinopathy*
- **Hemoglobinopathies** (e.g., sickle cell anemia, thalassemia) involve structural or quantitative defects in hemoglobin, often leading to **microcytic** or **hemolytic anemias** with **elevated reticulocyte counts** or specific red blood cell morphologies.
- The patient's **normocytic, normochromic anemia** and absent signs of hemolysis do not fit typical presentations of common hemoglobinopathies at this age.
*Congenital infection*
- Certain **congenital infections** (e.g., parvovirus B19, congenital syphilis, rubella) can cause anemia by directly suppressing erythropoiesis or causing hemolysis.
- While the mother was not immune to rubella, there are no other clinical signs of congenital infection, and the **normocytic, normochromic anemia** with low reticulocytes is more characteristic of anemia of prematurity.
Question 178: An 11-month-old boy presents with the recent loss of appetite and inability to gain weight. His diet consists mainly of cow’s milk and fruits. Family history is unremarkable. Physical examination shows conjunctival pallor. Laboratory findings are significant for the following:
Hemoglobin 9.1 g/dL
Mean corpuscular volume 75 μm3
Mean corpuscular hemoglobin 20 pg/cell
Red cell distribution width 18%
The patient is presumptively diagnosed with iron deficiency anemia (IDA) and ferrous sulfate syrup is prescribed. Which of the following laboratory values would most likely change 1st in response to this treatment?
A. ↓ Mentzer index
B. ↑ mean corpuscular hemoglobin
C. ↑ reticulocyte count (Correct Answer)
D. Normalization of hemoglobin
E. ↓ Anisocytosis
Explanation: ***↑ reticulocyte count***
- An increase in the **reticulocyte count** is the earliest sign of a bone marrow response to iron supplementation. Reticulocytes are immature red blood cells, and their production rapidly increases as the bone marrow utilizes available iron to make new healthy red blood cells.
- This typically occurs within **3-7 days** of initiating iron therapy, reflecting effective erythropoiesis before changes in hemoglobin or other red cell indices become apparent.
*↓ Mentzer index*
- The **Mentzer index** is used to differentiate between iron deficiency anemia and thalassemia trait; it is not a direct measure of treatment response.
- A low Mentzer index (MCV/RBC count < 13) suggests thalassemia, while a high index (MCV/RBC count > 13) suggests iron deficiency. This value would not be the first to change post-treatment.
*↑ mean corpuscular hemoglobin*
- **Mean corpuscular hemoglobin (MCH)** reflects the average amount of hemoglobin in a single red blood cell. While it will eventually increase with successful treatment, this change occurs after the reticulocyte count elevation.
- MCH improvement signifies the production of fully hemoglobinized red blood cells, which takes longer than the initial surge in immature red cell release.
*Normalization of hemoglobin*
- **Hemoglobin levels** will gradually rise and normalize with effective iron therapy, typically over several weeks to months.
- This is a later indicator of treatment success, occurring after the initial reticulocytosis.
*↓ Anisocytosis*
- **Anisocytosis** refers to variation in red blood cell size, measured by **red cell distribution width (RDW)**. In iron deficiency anemia, RDW is typically elevated.
- While RDW will eventually decrease as the red blood cell population becomes more uniform with treatment, this change is not the earliest response. The initial production of new red cells can even temporarily increase RDW before it normalizes.
Question 179: A 10-month-old infant is brought in by his parents because he is vomiting and not passing stool. His parents say he has vomited multiple times over the past couple of hours, but the most recent vomit was green. The patient has no significant past medical history. On physical examination, the patient is irritable and crying. On palpation in the periumbilical region, an abdominal mass is present. Emergency laparotomy is performed, which shows a part of the patient’s intestine folded into the section adjacent to it. Which of the following is the most likely diagnosis for this patient?
A. Pyloric stenosis
B. Hirschsprung’s disease
C. Duodenal atresia
D. Intussusception (Correct Answer)
E. Meckel’s diverticulum
Explanation: ***Intussusception***
- This diagnosis is highly suggested by the classic presentation of a 10-month-old infant with **bilious vomiting**, **abdominal pain** (irritability), and an **abdominal mass** in the periumbilical region, coupled with the surgical finding of one part of the intestine telescoping into an adjacent section.
- The sudden onset of symptoms in an otherwise healthy infant, along with **green vomit** (indicating bile) and an acute abdomen, are hallmark signs of this condition.
*Pyloric stenosis*
- This condition typically presents with **non-bilious projectile vomiting** in infants usually between 3 weeks and 6 months of age, with an **olive-shaped mass** in the epigastrium.
- The patient's **bilious vomiting** and the specific finding of intestinal telescoping rule out pyloric stenosis.
*Hirschsprung’s disease*
- This condition usually presents with **failure to pass meconium** in the neonatal period or chronic constipation and abdominal distension in older infants.
- While it involves the intestine, it is a **motility disorder** due to the absence of ganglion cells, not an anatomical telescoping of bowel.
*Duodenal atresia*
- This is a congenital obstruction of the duodenum, typically diagnosed shortly after birth with **bilious vomiting** and a characteristic "**double bubble**" sign on X-ray.
- It would not involve an abdominal mass or the intussusception described.
*Meckel’s diverticulum*
- This condition is a remnant of the vitelline duct and can present with painless rectal bleeding or, less commonly, intestinal obstruction, **volvulus**, or **intussusception** if it acts as a lead point.
- While it can be a rare cause of intussusception, the question directly describes the pathophysiology of intussusception itself rather than a diverticulum causing it.
Question 180: A 3-year-old boy is brought to the physician by his mother for the evaluation of delay in attaining developmental milestones. He could sit upright by 14 months and has not been able to walk without support. He can build a tower of 3 blocks and cannot use utensils to feed himself. He speaks in unclear 2-word phrases and cannot draw a circle yet. His mother has noticed him hitting his head against the wall on multiple occasions. He is at 20th percentile for height and at 50th percentile for weight. Vitals signs are within normal limits. Examination shows multiple lacerations of his lips and tongue. There are multiple healing wounds over his fingers. Neurological examination shows increased muscle tone in all extremities. Laboratory studies show:
Hemoglobin 10.1 g/dL
Mean corpuscular volume 103 μm3
Serum
Na+ 142 mEq/L
Cl- 101 mEq/:
K+ 4.1 mEq/L
Creatinine 1.6 mg/dL
Uric acid 12.3 mg/dL
Which of the following is the most likely cause of this patient's findings?
A. FMR1 gene mutation
B. Branched-chain alpha-ketoacid dehydrogenase complex deficiency
C. MECP2 gene mutation
D. Microdeletion of paternal chromosome 15
E. Hypoxanthine-guanine phosphoribosyltransferase deficiency (Correct Answer)
Explanation: **Hypoxanthine-guanine phosphoribosyltransferase deficiency**
- The combination of **developmental delay**, **self-mutilation** (lacerations of lips/tongue, head-hitting, finger wounds), **hyperuricemia** (uric acid 12.3 mg/dL), and **increased muscle tone** are hallmark features of **Lesch-Nyhan syndrome**, caused by deficiency of **hypoxanthine-guanine phosphoribosyltransferase (HGPRT)**.
- The elevated **mean corpuscular volume (MCV)** suggests **macrocytic anemia**, which can also be seen in Lesch-Nyhan syndrome due to impaired purine metabolism.
*FMR1 gene mutation*
- This mutation causes **Fragile X syndrome**, characterized by intellectual disability, developmental delay, and behavioral issues like hyperactivity or autism-like features.
- However, **self-mutilation** and **hyperuricemia** are not typical features of Fragile X syndrome.
*Branched-chain alpha-ketoacid dehydrogenase complex deficiency*
- This deficiency leads to **Maple Syrup Urine Disease (MSUD)**, presenting with poor feeding, lethargy, seizures, and a characteristic maple syrup odor in urine.
- The clinical presentation, including the absence of a distinct odor and the presence of self-mutilation and hyperuricemia, does not align with MSUD.
*MECP2 gene mutation*
- This mutation is associated with **Rett syndrome**, which primarily affects girls, causing a period of normal development followed by regression, loss of purposeful hand movements, and stereotypic hand-wringing.
- The patient is a boy, and the specific symptoms described, especially hyperuricemia and severe self-mutilation, are not consistent with Rett syndrome.
*Microdeletion of paternal chromosome 15*
- This describes the genetic cause of **Prader-Willi syndrome**, characterized by infantile hypotonia, cryptorchidism, developmental delay, and later in childhood, hyperphagia and obesity.
- While there is developmental delay, the clinical picture here lacks the characteristic features of Prader-Willi syndrome and includes symptoms (self-mutilation, hyperuricemia) not typically seen in this condition.