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Terminal complement deficiency — MRCPCH TAS MCQ

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HardImmunologyTerminal complement deficiencyMRCPCH TAS

A 12-year-old has a second episode of meningococcal sepsis. Immunoglobulins, lymphocyte subsets and neutrophil oxidative burst are normal. Which immune defect is most likely?

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Correct answer: D — Terminal complement pathway deficiency

Recurrent invasive Neisseria infection with otherwise normal immune testing suggests terminal complement deficiency involving C5-C9. BTK mutation would cause recurrent sinopulmonary infections with low immunoglobulins. The pearl is that complement testing is important after recurrent meningococcal disease.

Reference: Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi; UKHSA Green Book