A 10-month-old infant with failure to thrive and recurrent sinopulmonary infections has bulky, foul-smelling, greasy stools. Sweat chloride testing reveals a chloride concentration of 75 mEq/L (normal < 30 mEq/L). What is the underlying genetic defect?
Answer and explanation
Correct answer: C. Mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene
- Step 1: A sweat chloride concentration >= 60 mEq/L confirms the diagnosis of cystic fibrosis.
- Step 2: Cystic fibrosis is an autosomal recessive disease caused by mutations in the CFTR gene on chromosome 7, which encodes an ATP-binding chloride channel.
- Step 3: Defective chloride transport leads to thick, viscous secretions in lungs and pancreatic duct obstruction.
Answer
Mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.
Practise more General Pediatrics and Neonatal Medicine.
Free questions with an explanation for every one, and full timed Lebanese Medical Colloquium (Colloquium Liban) mock tests.
More General Pediatrics and Neonatal Medicine questions
- A 2-year-old boy presents with sudden barking cough, inspiratory stridor, and hoarseness that worsens at night. He is afebrile and in mild r…
- A 4-year-old child presents with high fever (39.8°C), severe sore throat, difficulty swallowing, drooling, and sits upright leaning forward…
- A 3-year-old boy presents with 6 days of persistent high fever, bilateral non-purulent conjunctival injection, cracked red lips, strawberry…
- A 6-month-old infant presents during winter with rhinorrhea, low-grade fever, tachypnea, expiratory wheezing, and bilateral subcostal retrac…
- A 3-week-old full-term male presents with forceful non-bilious projectile vomiting after every feed. He is ravenously hungry. Physical exami…
- What classic serum electrolyte abnormality is produced by persistent severe vomiting in infantile hypertrophic pyloric stenosis?