Pediatric gastrointestinal infections US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Pediatric gastrointestinal infections. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Pediatric gastrointestinal infections US Medical PG Question 1: A 62-year-old man presents to the emergency department with confusion. The patient’s wife states that her husband has become more somnolent over the past several days and now is very confused. The patient has no complaints himself, but is answering questions inappropriately. The patient has a past medical history of diabetes and hypertension. His temperature is 98.3°F (36.8°C), blood pressure is 127/85 mmHg, pulse is 138/min, respirations are 14/min, and oxygen saturation is 99% on room air. Physical exam is notable for a confused man with dry mucous membranes. Initial laboratory studies are ordered as seen below.
Serum:
Na+: 135 mEq/L
Cl-: 100 mEq/L
K+: 3.0 mEq/L
HCO3-: 23 mEq/L
BUN: 30 mg/dL
Glucose: 1,299 mg/dL
Creatinine: 1.5 mg/dL
Ca2+: 10.2 mg/dL
Which of the following is the most appropriate initial treatment for this patient?
- A. Insulin, normal saline, and potassium (Correct Answer)
- B. Normal saline and potassium
- C. Insulin and potassium
- D. Insulin
- E. Insulin and normal saline
Pediatric gastrointestinal infections Explanation: ***Insulin, normal saline, and potassium***
- This patient is presenting with **hyperosmolar hyperglycemic state (HHS)**, characterized by severe hyperglycemia (glucose 1299 mg/dL), dehydration (dry mucous membranes, high BUN and creatinine), and altered mental status. The initial treatment involves intravenous fluids to correct dehydration, insulin to lower blood glucose, and potassium supplementation due to potential shifts as insulin is administered.
- **Normal saline** addresses the severe dehydration, **insulin** corrects hyperglycemia, and **potassium supplementation** prevents hypokalemia, which is common during HHS treatment as glucose and potassium shift intracellularly.
*Normal saline and potassium*
- While **normal saline** and **potassium** are crucial for rehydration and electrolyte balance, omitting **insulin** would fail to address the core problem of severe hyperglycemia in HHS.
- Without insulin, blood glucose levels will remain dangerously high, leading to persistent osmotic diuresis and worsening dehydration.
*Insulin and potassium*
- Administering **insulin** without addressing the profound **dehydration** with intravenous fluids can lead to **hypovolemic shock** as insulin further drives glucose and water into cells.
- Rehydration is the priority in HHS management before or concurrent with insulin administration.
*Insulin*
- Giving only **insulin** would be detrimental, as the patient is severely dehydrated and hypokalemic (K+ 3.0 mEq/L, and will drop further with insulin).
- This approach would exacerbate dehydration and could cause life-threatening arrhythmias due to severe hypokalemia.
*Insulin and normal saline*
- While addressing hyperglycemia and dehydration, omitting **potassium supplementation** is dangerous because insulin drives potassium into cells, potentially causing severe **hypokalemia** and cardiac arrhythmias.
- The patient already has a low-normal potassium level, which will likely drop further with insulin treatment.
Pediatric gastrointestinal infections US Medical PG Question 2: A 21-year-old male presents after several days of flatulence and greasy, foul-smelling diarrhea. The patient reports symptoms of nausea and abdominal cramps followed by sudden diarrhea. He says that his symptoms started after he came back from a camping trip. When asked about his camping activities, he reports that his friend collected water from a stream, but he did not boil or chemically treat the water. His temperature is 98.6°F (37°C), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 122/98 mm Hg. Stool is sent for microscopy which returns positive for motile protozoans. Which of the following antibiotics should be started in this patient?
- A. Vancomycin
- B. Erythromycin
- C. Cephalexin
- D. Ciprofloxacin
- E. Metronidazole (Correct Answer)
Pediatric gastrointestinal infections Explanation: ***Metronidazole***
- This patient's symptoms (greasy, foul-smelling diarrhea, flatulence) after consuming untreated stream water are highly suggestive of **Giardiasis**, caused by *Giardia lamblia*.
- **Metronidazole** is the first-line antibiotic for treating Giardiasis due to its efficacy against anaerobic parasites and protozoa.
*Vancomycin*
- **Vancomycin** is primarily used for serious gram-positive bacterial infections, particularly **methicillin-resistant *Staphylococcus aureus* (MRSA)** and *Clostridioides difficile* colitis.
- It has no activity against protozoal infections like Giardiasis.
*Erythromycin*
- **Erythromycin** is a macrolide antibiotic effective against a range of bacterial infections, including atypical pneumonia and certain sexually transmitted infections.
- It is not effective against protozoal parasites.
*Cephalexin*
- **Cephalexin** is a first-generation cephalosporin antibiotic used to treat bacterial infections such as skin and soft tissue infections, strep throat, and urinary tract infections.
- It does not have activity against protozoans.
*Ciprofloxacin*
- **Ciprofloxacin** is a fluoroquinolone antibiotic used for various bacterial infections, including urinary tract infections, gastrointestinal infections (e.g., traveler's diarrhea caused by bacteria), and respiratory tract infections.
- While effective against many bacteria, it is not the primary treatment for protozoal infections like Giardiasis.
Pediatric gastrointestinal infections US Medical PG Question 3: A 2-year-old male presents to the emergency department with fatigue and lethargy. Upon presentation, the patient is found to be severely dehydrated. The patient's mother says that he has been having non-bloody diarrhea for a day. She also says that the patient has not received any vaccinations after 6 months and currently attends a daycare center. Which of the following organisms is most likely responsible for the symptoms seen in this child?
- A. Campylobacter jejuni
- B. Norovirus
- C. Shigella
- D. Salmonella
- E. Rotavirus (Correct Answer)
Pediatric gastrointestinal infections Explanation: ***Rotavirus***
- The presentation of severe **dehydration** due to **non-bloody diarrhea** in an **unvaccinated** 2-year-old attending daycare is highly characteristic of **rotavirus gastro-enteritis**.
- Rotavirus is a common cause of severe infantile diarrhea and is notable for causing **epidemics in daycare settings** due to its easy transmission and high infectivity.
*Campylobacter jejuni*
- This typically causes **bloody diarrhea**, which is not seen in the patient's presentation.
- While it can occur in children, the sudden onset of severe dehydration with non-bloody diarrhea is less typical for *Campylobacter*.
*Norovirus*
- Norovirus is a common cause of **gastroenteritis** with vomiting and diarrhea in children and adults.
- However, rotavirus more commonly leads to **severe dehydration** requiring hospitalization in very young children, especially in unvaccinated populations.
*Shigella*
- *Shigella* infections commonly cause **dysentery**, characterized by **bloody stools**, fever, and cramps, which is not present in this case.
- While *Shigella* can cause severe illness, the history of non-bloody diarrhea makes it less likely.
*Salmonella*
- *Salmonella* gastroenteritis often presents with **fever**, **abdominal cramps**, and **bloody or non-bloody diarrhea**.
- However, it is less commonly associated with the rapid onset of severe dehydration in this age group compared to rotavirus, particularly with no mention of fever or other systemic symptoms.
Pediatric gastrointestinal infections US Medical PG Question 4: A mother brings her 4-year-old boy to the physician, as the boy has a 7-day history of foul-smelling diarrhea, abdominal cramps, and fever. The mother adds that he has been vomiting as well, and she is very much worried. The child is in daycare, and the mother endorses sick contacts with both family and friends. The boy has not been vaccinated as the parents do not think it is necessary. On physical exam, the child appears dehydrated. Stool examination is negative for blood cells, pus, and ova or parasites. What is the most likely diagnosis?
- A. Rotavirus infection (Correct Answer)
- B. Cryptosporidiosis
- C. Irritable bowel syndrome
- D. C. difficile colitis
- E. Norovirus infection
Pediatric gastrointestinal infections Explanation: ***Rotavirus infection***
- The classic presentation of **foul-smelling diarrhea**, vomiting, abdominal cramps, and fever in an **unvaccinated child** attending daycare strongly suggests rotavirus. This virus is a common cause of **severe gastroenteritis** in young children.
- The absence of bacterial or parasitic indicators in the stool (blood cells, pus, ova/parasites) further narrows the diagnosis to a **viral cause**, with rotavirus being highly prevalent in this age group, especially without vaccination.
*Cryptosporidiosis*
- While it causes **watery diarrhea** and abdominal cramps, it is typically associated with **contaminated water sources** and often produces **oocysts** detectable in stool, which were not found in this case.
- The symptoms in the child are more classic for a common viral gastroenteritis rather than a parasitic infection, especially given the **absence of parasitic elements** on examination.
*Irritable bowel syndrome*
- **IBS** is a chronic functional gastrointestinal disorder and rarely presents acutely with fever and vomiting in a 4-year-old.
- Its diagnosis involves specific **Rome IV criteria** related to chronic abdominal pain and changes in bowel habits, which are not met by the acute presentation here.
*C. difficile colitis*
- **C. difficile colitis** typically follows **antibiotic use** or is acquired in healthcare settings and commonly causes **bloody diarrhea** and significant abdominal pain.
- The diarrhea is usually more profuse and the stool may contain **leukocytes** or be positive for C. difficile toxin, neither of which is indicated in the patient's presentation.
*Norovirus infection*
- Norovirus causes acute gastroenteritis with **vomiting** and **diarrhea**, but the diarrhea is often less foul-smelling and of shorter duration than described.
- While possible, the classic triad of **foul-smelling diarrhea, vomiting, and fever** in an unvaccinated child with sick contacts more strongly points to rotavirus, which tends to cause more severe and prolonged symptoms in young, unvaccinated children.
Pediatric gastrointestinal infections US Medical PG Question 5: An 8-year old boy is brought to the emergency department because he has been lethargic and has had several episodes of nausea and vomiting for the past day. He has also had increased thirst over the past two months. He has lost 5.4 kg (11.9 lbs) during this time. He is otherwise healthy and has no history of serious illness. His temperature is 37.5 °C (99.5 °F), blood pressure is 95/68 mm Hg, pulse is 110/min, and respirations are 30/min. He is somnolent and slightly confused. His mucous membranes are dry. Laboratory studies show:
Hemoglobin 16.2 g/dL
Leukocyte count 9,500/mm3
Platelet count 380,000/mm3
Serum
Na+ 130 mEq/L
K+ 5.5 mEq/L
Cl- 99 mEq/L
HCO3- 16 mEq/L
Creatinine 1.2 mg/dL
Glucose 570 mg/dL
Ketones positive
Blood gases, arterial
pH 7.25
pCO2 21 mm Hg
Which of the following is the most appropriate next step in management?
- A. Intravenous hydration with 0.45% normal saline and insulin
- B. Intravenous hydration with 5% dextrose solution and 0.45% normal saline
- C. Intravenous sodium bicarbonate
- D. Intravenous hydration with 0.9% normal saline and insulin (Correct Answer)
- E. Intravenous hydration with 0.9% normal saline and potassium chloride
Pediatric gastrointestinal infections Explanation: ***Intravenous hydration with 0.9% normal saline and insulin***
- This patient presents with **diabetic ketoacidosis (DKA)**, characterized by hyperglycemia (glucose 570 mg/dL), metabolic acidosis (pH 7.25, HCO3- 16 mEq/L, ketones positive), and dehydration (dry mucous membranes, increased thirst, weight loss).
- Initial management of DKA involves aggressive **volume expansion** with **0.9% normal saline** to restore perfusion and reduce hyperglycemia; subsequently, **insulin infusion** is started to correct hyperglycemia and halt ketogenesis.
*Intravenous hydration with 0.45% normal saline and insulin*
- While insulin is crucial, **0.45% normal saline (hypotonic saline)** is generally not the initial fluid of choice for DKA due to the risk of exacerbating cerebral edema, especially in children.
- **Isotonic saline (0.9% normal saline)** is preferred for initial resuscitation to rapidly restore extracellular fluid volume.
*Intravenous hydration with 5% dextrose solution and 0.45% normal saline*
- **5% dextrose solution** should only be added to intravenous fluids when the blood glucose level falls to around 200-250 mg/dL, to prevent hypoglycemia while continuing insulin to resolve ketosis.
- Administering dextrose initially would worsen the existing severe hyperglycemia.
*Intravenous sodium bicarbonate*
- **Sodium bicarbonate** is generally not recommended for mild to moderate DKA due to potential risks like cerebral edema and metabolic alkalosis, and potential paradoxical worsening of CNS acidosis.
- Bicarbonate therapy is reserved for **severe acidosis (pH < 6.9 or 7.0)** with hemodynamic instability or impaired cardiac contractility, which is not the case here.
*Intravenous hydration with 0.9% normal saline and potassium chloride*
- While **0.9% normal saline** is appropriate, this option lacks **insulin therapy**, which is essential for treating DKA by halting ketogenesis and correcting hyperglycemia.
- Although potassium supplementation will be necessary during DKA treatment (as insulin drives K+ into cells and can cause hypokalemia), the most appropriate **next step** is to initiate both fluid resuscitation and insulin therapy together.
- The patient's current potassium level of 5.5 mEq/L is at the upper limit of normal, but reflects total body potassium depletion; potassium should be added to maintenance fluids once adequate urine output is established.
Pediatric gastrointestinal infections US Medical PG Question 6: A 34-year-old man presents with a 2-day history of loose stools, anorexia, malaise, and abdominal pain. He describes the pain as moderate, cramping in character, and diffusely localized to the periumbilical region. His past medical history is unremarkable. He works as a wildlife photographer and, 1 week ago, he was in the Yucatan peninsula capturing the flora and fauna for a magazine. The vital signs include blood pressure 120/60 mm Hg, heart rate 90/min, respiratory rate 18/min, and body temperature 38.0°C (100.4°F). Physical examination is unremarkable. Which of the following is a characteristic of the microorganism most likely responsible for this patient’s symptoms?
- A. Disabling Gi alpha subunit
- B. Production of lecithinase
- C. Overactivation of guanylate cyclase (Correct Answer)
- D. Inactivation of the 60S ribosomal subunit
- E. Presynaptic vesicle dysregulation
Pediatric gastrointestinal infections Explanation: ***Overactivation of guanylate cyclase***
- The patient's symptoms (loose stools, abdominal cramping, recent travel to the Yucatan Peninsula) are highly suggestive of **traveler's diarrhea**, most commonly caused by **enterotoxigenic E. coli (ETEC)**.
- ETEC produces a **heat-stable toxin (ST)** that binds to the **guanylate cyclase C receptor** on intestinal epithelial cells, leading to **increased intracellular cGMP** and subsequent **chloride and water secretion**.
*Disabling Gi alpha subunit*
- This mechanism is characteristic of **pertussis toxin** (from *Bordetella pertussis*), which **ADP-ribosylates and inactivates the Gi protein**, preventing inhibition of adenylate cyclase.
- Pertussis toxin is associated with **whooping cough**, not gastrointestinal disease or traveler's diarrhea.
- Note: **Cholera toxin** works via a different mechanism—it **activates Gs alpha subunit** to increase cAMP, causing severe watery diarrhea, but the clinical presentation here (mild symptoms, travel to endemic area) favors ETEC over cholera.
*Production of lecithinase*
- **Lecithinase (alpha-toxin)** is a characteristic virulence factor of **Clostridium perfringens**, causing gas gangrene and some food poisoning, not the watery diarrhea described here.
- It acts as a phospholipase, disrupting cell membranes.
*Inactivation of the 60S ribosomal subunit*
- This mechanism is associated with **Shiga toxin** produced by **enterohemorrhagic E. coli (EHEC)** and **Shigella dysenteriae**.
- These typically cause **bloody diarrhea** and **hemolytic uremic syndrome (HUS)**, which are not described in this patient.
*Presynaptic vesicle dysregulation*
- This mechanism is characteristic of **botulinum toxin** (from *Clostridium botulinum*), which **cleaves SNARE proteins** and prevents acetylcholine release, causing flaccid paralysis.
- It is not involved in bacterial gastroenteritis causing diarrhea.
Pediatric gastrointestinal infections US Medical PG Question 7: An 18-month-old boy is brought to the physician by his parents for the evaluation of passing large amounts of dark red blood from his rectum for 2 days. His parents noticed that he has also had several episodes of dark stools over the past 3 weeks. The parents report that their child has been sleeping more and has been more pale than usual over the past 24 hours. The boy's appetite has been normal and he has not vomited. He is at the 50th percentile for height and 50th percentile for weight. His temperature is 37°C (98.6°F), pulse is 135/min, respirations are 38/min, and blood pressure is 90/50 mm Hg. Examination shows pale conjunctivae. The abdomen is soft and nontender. There is a small amount of dark red blood in the diaper. Laboratory studies show:
Hemoglobin 9.5 g/dL
Hematocrit 30%
Mean corpuscular volume 68 μm3
Leukocyte count 7,200/mm3
Platelet count 300,000/mm3
Which of the following is most likely to confirm the diagnosis?
- A. Colonoscopy
- B. Water-soluble contrast enema
- C. Technetium-99m pertechnetate scan (Correct Answer)
- D. Esophagogastroduodenoscopy
- E. Plain abdominal x-ray
Pediatric gastrointestinal infections Explanation: **Technetium-99m pertechnetate scan**
- The presentation of painless **dark red rectal bleeding** in a toddler, coupled with signs of **anemia** (pale conjunctivae, hemoglobin 9.5 g/dL, MCV 68 μm³), strongly suggests a **Meckel's diverticulum** with ectopic gastric mucosa.
- A **Technetium-99m pertechnetate scan** specifically detects **ectopic gastric mucosa**, which is the most common cause of bleeding in a Meckel's diverticulum, making it the definitive diagnostic test.
*Colonoscopy*
- While useful for evaluating lower gastrointestinal bleeding, a **colonoscopy** is less likely to detect a Meckel's diverticulum, which often lies beyond the reach of a standard colonoscope.
- It involves more invasive preparation and carries higher risks for a young child compared to a nuclear scan for this specific suspicion.
*Water-soluble contrast enema*
- A **water-soluble contrast enema** is primarily used to diagnose conditions like intussusception or colonic obstructions by visualizing the bowel lumen.
- It is unlikely to visualize a Meckel's diverticulum or identify the bleeding source directly, especially one involving ectopic gastric mucosa.
*Esophagogastroduodenoscopy*
- An **esophagogastroduodenoscopy (EGD)** evaluates the upper gastrointestinal tract (esophagus, stomach, duodenum).
- The symptom of **dark red rectal bleeding** indicates a lower GI source, making an EGD a less appropriate initial diagnostic step.
*Plain abdominal x-ray*
- A **plain abdominal x-ray** is useful for identifying bowel obstruction, perforation, or foreign bodies, but it does not directly visualize or diagnose causes of GI bleeding like a Meckel's diverticulum.
- It provides limited information regarding the source of internal bleeding or the presence of anomalous tissue.
Pediatric gastrointestinal infections US Medical PG Question 8: A 3-year-old girl is brought to the emergency room because of a 5-day history of high fever and fatigue. During this time she has been crying more than usual and eating less. Her mother says that the child has also complained about pain in her arms and legs for the past 3 days. She was born at term and has been otherwise healthy. She appears ill. Her temperature is 39.5°C (103.1°F), pulse is 128/min, and blood pressure is 96/52 mm Hg. The lungs are clear to auscultation. A grade 3/6 systolic murmur is heard at the apex. There is mild tenderness to palpation of the left upper quadrant with no guarding or rebound. The spleen is palpated 3 cm below the left costal margin. There is no redness or swelling of the joints. Laboratory studies show:
Hemoglobin 11.8 g/dL
Leukocyte count 16,300/mm3
Platelet count 220,000/mm3
Erythrocyte sedimentation rate 50 mm/h
Serum
Glucose 96 mg/dL
Creatinine 1.7 mg/dL
Total bilirubin 0.4 mg/dL
AST 18 U/L
ALT 20 U/L
Urine
Protein 2+
RBC casts rare
RBC 10/hpf
WBC 1–2/hpf
Which of the following is the most appropriate next step in management?
- A. Obtain a transesophageal echocardiography
- B. Administer intravenous vancomycin
- C. Obtain a renal biopsy
- D. Measure rheumatoid factors
- E. Obtain 3 sets of blood cultures (Correct Answer)
Pediatric gastrointestinal infections Explanation: ***Obtain 3 sets of blood cultures***
- The patient presents with **fever, new murmur**, and **splenomegaly**, in addition to elevated ESR and proteinuria. These findings are highly suggestive of **infective endocarditis**, which requires urgent diagnosis via blood cultures.
- Blood cultures are essential to identify the causative organism for targeted antibiotic therapy and confirm the diagnosis of endocarditis.
*Obtain a transesophageal echocardiography*
- While echocardiography is crucial for diagnosing endocarditis, **blood cultures should be obtained first** to identify the pathogen before initiating empiric antibiotics.
- Transesophageal echocardiography (TEE) provides superior visualization of vegetations compared to transthoracic echo (TTE) but is usually performed after positive blood cultures or if TTE is inconclusive.
*Administer intravenous vancomycin*
- Administering antibiotics prior to obtaining blood cultures can **sterilize the blood**, making it difficult to identify the causative organism and select effective definitive treatment.
- Empiric antibiotic therapy, such as vancomycin, is typically initiated after blood cultures are drawn, especially if the patient is severely ill and infective endocarditis is highly suspected.
*Obtain a renal biopsy*
- The patient has elevated creatinine and proteinuria with RBC casts, suggesting **glomerulonephritis**, which can be a complication of infective endocarditis or other systemic diseases.
- However, a renal biopsy is an invasive procedure and generally not the initial step in management for a sick child with suspected endocarditis, as the primary concern is the cardiac infection.
*Measure rheumatoid factors*
- Rheumatoid factors are associated with **rheumatoid arthritis** and other autoimmune conditions, which do not fully explain the constellation of symptoms (fever, new murmur, splenomegaly, elevated ESR, renal involvement) seen in this patient.
- While some autoimmune conditions can cause similar symptoms, the acute presentation with fever and a new murmur points more strongly towards an infectious etiology like endocarditis.
Pediatric gastrointestinal infections US Medical PG Question 9: A 12-year-old boy is brought in by his mother to the emergency department. He has had abdominal pain, fever, nausea, vomiting, and loss of appetite since yesterday. At first, the mother believed it was just a "stomach flu," but she is growing concerned about his progressive decline. Vitals include: T 102.3 F, HR 110 bpm, BP 120/89 mmHg, RR 16, O2 Sat 100%. Abdominal exam is notable for pain over the right lower quadrant. What is the next best step in management in addition to IV hydration and analgesia?
- A. Upright and supine abdominal radiographs
- B. Abdominal MRI with gadolinium contrast
- C. Abdominal CT scan with IV contrast
- D. Right lower quadrant ultrasound (Correct Answer)
- E. Abdominal CT scan with IV and PO contrast
Pediatric gastrointestinal infections Explanation: ***Right lower quadrant ultrasound***
- In a 12-year-old boy with suspected **appendicitis**, **ultrasound** is the preferred initial imaging modality due to its **lack of radiation** and high diagnostic accuracy in this population.
- It effectively identifies an inflamed **appendix**, periappendiceal fluid, and other relevant findings while avoiding radiation exposure, which is particularly important in children.
*Upright and supine abdominal radiographs*
- **Plain abdominal X-rays** are generally not useful for diagnosing appendicitis as they often do not visualize the appendix directly.
- While they can rule out other causes of abdominal pain like **bowel obstruction** or **perforation** (free air), they lack the sensitivity and specificity for appendicitis.
*Abdominal MRI with gadolinium contrast*
- **MRI** is an excellent alternative to CT, especially in pregnant patients, but it is **less readily available** and consumes more time than ultrasound in an emergent setting for a pediatric patient.
- Though it provides good soft tissue detail without radiation, its **cost and accessibility** make it less practical as a first-line imaging test for suspected appendicitis in children.
*Abdominal CT scan with IV contrast*
- An **abdominal CT scan with IV contrast** is highly accurate for diagnosing appendicitis, but it involves significant **ionizing radiation**, which should be minimized in pediatric patients.
- It is typically reserved for cases where ultrasound findings are equivocal or other diagnoses are strongly suspected, or when the patient is older or body habitus limits ultrasound utility.
*Abdominal CT scan with IV and PO contrast*
- Adding **oral contrast** to a CT scan significantly increases the time before imaging can be performed, which is not ideal in an acute emergency like suspected appendicitis.
- While it can help delineate bowel loops, the additional contrast and associated delay are usually **unnecessary** for diagnosing appendicitis and further expose the child to radiation.
Pediatric gastrointestinal infections US Medical PG Question 10: An 8-year-old boy presents to his pediatrician accompanied by his father with a complaint of chronic cough. For the past 2 months he has been coughing up yellow, foul-smelling sputum. He has been treated at a local urgent care center for multiple episodes of otitis media, sinusitis, and bronchitis since 2 years of age. His family history is unremarkable. At the pediatrician's office, his temperature is 99.2°F (37.3°C), blood pressure is 110/84 mmHg, pulse is 95/min, and respirations are 20/min. Inspection shows a young boy who coughs occasionally during examination. Pulmonary exam demonstrates diffuse wheezing and crackles bilaterally. Mild clubbing is present on the fingers. The father has brought an electrocardiogram (ECG) from the patient’s last urgent care visit that shows pronounced right axis deviation. Which of the following is the most likely etiology of this patient’s condition?
- A. Failure of neural crest cell migration
- B. Maldevelopment of pharyngeal pouches
- C. Transient bronchoconstriction
- D. Defective maturation of B-lymphocytes
- E. Decreased motility of cilia (Correct Answer)
Pediatric gastrointestinal infections Explanation: ***Decreased motility of cilia***
- The recurrent respiratory infections (**otitis media, sinusitis, bronchitis**), chronic productive cough with **foul-smelling sputum**, and **bronchiectasis** (implied by chronic cough, wheezing, crackles) are highly suggestive of **primary ciliary dyskinesia (PCD)**.
- **Clubbing** and **right axis deviation** (suggesting right ventricular hypertrophy from pulmonary hypertension) are complications of chronic lung disease such as severe bronchiectasis, which is characteristic of PCD.
*Failure of neural crest cell migration*
- This is associated with conditions like **DiGeorge syndrome** or **Hirschsprung disease**, which present with different clinical features (e.g., cardiac defects, hypocalcemia, intestinal obstruction).
- It does not directly explain the recurrent respiratory tract infections and bronchiectasis seen in this patient.
*Maldevelopment of pharyngeal pouches*
- Similar to neural crest cell defects, issues with pharyngeal pouch development (e.g., **DiGeorge syndrome**) affect the immune system and cardiac structures.
- While it can lead to recurrent infections, it typically involves **T-cell deficiencies** and specific cardiac anomalies, rather than chronic suppurative respiratory disease and bronchiectasis as the primary presentation.
*Transient bronchoconstriction*
- This describes conditions like **asthma**, which causes reversible airway narrowing and wheezing.
- However, asthma does not explain the chronic **foul-smelling sputum**, **clubbing**, persistent recurrent infections like otitis media and sinusitis, or the development of bronchiectasis.
*Defective maturation of B-lymphocytes*
- This leads to **immunodeficiencies** primarily affecting **antibody production**, such as **X-linked agammaglobulinemia**.
- While patients would experience recurrent bacterial infections, the specific pattern of chronic sinusitis, otitis, and bronchiectasis with **foul-smelling sputum** (suggesting chronic bacterial colonization and impaired clearance) points more towards a structural or ciliary defect than a purely humoral immune deficiency.
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