Counsel a family on recurrent meningococcal disease and a terminal complement deficiency — OSCE

Candidate brief

You have eight minutes to counsel the parents of a fourteen-year-old boy in whom you suspect a terminal complement deficiency after his second episode of invasive meningococcal disease. The specific component is not yet confirmed. Use a structured, honest, empathic approach. [1] [2]

Key teaching and communication objectives

Acknowledge and validate the parents' fear and guilt before delivering information. Explain that the condition is genetic but not anyone's fault, that it affects a specific part of the immune system that lyses one particular bacterium — the meningococcus — which is why he is otherwise completely well and why the recurrent meningococcal disease is not "bad luck" but a recognisable pattern. [1] [4]

Explain the next steps in plain language: a repeat total haemolytic complement test on a fresh sample to confirm, then identification of the specific missing component and genetic testing, because the right prevention plan depends on confirming the defect rather than acting on a single abnormal result. Address the "why is he so well" paradox honestly: most of the immune system is intact, and the missing piece is narrow, which is exactly why the prognosis is good with prevention. [2] [4]

Describe what prevention involves: meningococcal ACWY and B vaccination, continuous low-dose antibiotic prophylaxis, and a supply of emergency antibiotics to start immediately at the first sign of febrile illness with a clear instruction to present to hospital. Be honest that vaccination does not eliminate the risk — which is why the antibiotics are added, not substituted — and that the aim is to make a dangerous infection rare and treatable rather than to erase it. [2] [3]

Mention the family implications: because the maternal uncle died of meningococcal meningitis, screening of the wider family — and specifically testing for the X-linked properdin deficiency if the pattern fits — is part of the plan. Frame this as protection for relatives, not as blame. Close with a shared plan and a clear next appointment, an offer of written information and a patient-support organisation, and a single sentence the family can repeat: "he is well, his immune system is mostly intact, and we are protecting the one gap." [1] [3]