Mitochondrial inheritance — MRCPCH TAS MCQ

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ModerateGeneticsMitochondrial inheritanceMRCPCH TAS

A 9-year-old girl has exercise intolerance, sensorineural deafness and recurrent lactic acidosis. Her mother and maternal aunt have milder hearing impairment. What is the most likely inheritance pattern?

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Correct answer: B — Mitochondrial inheritance

Mitochondrial DNA is transmitted through the oocyte, so affected mothers can transmit disease to children of either sex. X-linked recessive disease would preferentially affect males and would not usually show maternal-line transmission in both sexes. Heteroplasmy explains why severity may vary between relatives.

Reference: Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi; Lissauer's Illustrated Textbook of Paediatrics