Inheritance pattern of cystic fibrosis — MRCPCH TAS MCQ

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EasyGeneticsInheritance pattern of cystic fibrosisMRCPCH TAS

A 5-week-old infant has faltering growth, recurrent cough and a positive newborn blood spot screen. Sweat chloride is raised and both parents are clinically well. What is the most likely inheritance pattern?

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Correct answer: A — Autosomal recessive

Cystic fibrosis classically follows autosomal recessive inheritance, so unaffected carrier parents can have an affected child. Autosomal dominant disease would usually show vertical transmission, which is not suggested here. A key pearl is that recurrence risk for future pregnancies is 25% when both parents are carriers.

Reference: RCPCH Theory examination syllabi; Nelson Textbook of Pediatrics; NICE NG78 cystic fibrosis