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Complement deficiency — RACP Paediatrics MCQ

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HardIDComplement deficiencyRACP Paediatrics

A 6-year-old has had 3 episodes of meningococcal meningitis. Between episodes the child is well. Immunoglobulin levels and lymphocyte subsets are normal. What is the most likely underlying immunodeficiency?

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Correct answer: C — Complement deficiency

Recurrent Neisseria meningitidis infections (meningococcal disease) with normal immunoglobulins and lymphocyte subsets should raise suspicion for a terminal complement pathway deficiency (C5-C9, properdin). Complement screening (CH50 and AP50) should be performed. These patients require meningococcal vaccination with all available serogroups and may need antibiotic prophylaxis.

Reference: RCH Melbourne – 2023 – Immunodeficiency CPG; RACP Paediatric Curriculum – Immunology