OSCE — Meltzer triad and cold-precipitating immunoglobulins: manage cryoglobulinaemic disease

Brief (to candidate)

A 58-year-old with chronic hepatitis C develops recurrent lower-limb palpable purpura, arthralgia and fatigue. Complements show very low C4 with near-normal C3. RF is positive. A second card describes a patient with Waldenström macroglobulinaemia, headache and blurred vision in the cold. You have 8 minutes to classify cryoglobulinaemia, plan correct laboratory handling, and escalate therapy for vasculitis vs hyperviscosity.

Candidate instructions

1. Explain the Brouet Type I / II / III classification.
2. Recognise Meltzer's triad and the low C4 pattern in mixed disease.
3. Link HCV (and other causes) and list required screens.
4. Describe pre-analytical sample handling for cryoglobulin assay.
5. Outline therapy: antiviral, rituximab, steroids, plasma exchange by severity/type.

Examiner checklist (mark each domain / 10)

Model key actions

• Classify Type I vs mixed and recognise purpura–arthralgia–weakness + low C4 as mixed cryoglobulinaemia.^[1]
• Always warm-handle cryoglobulin samples; screen HCV and paraprotein.^[2]
• Use rituximab ± PE for severe mixed vasculitis; treat the clone or virus driving production.^[6]

Common errors

• Sending cryoglobulin sample on ice/room-temp incorrectly.
• Missing HCV testing in mixed disease.
• Treating Type I hyperviscosity as simple rash without haematology/PE.
• Ignoring renal/neurologic involvement.
• Using prolonged steroids alone without addressing B-cell/virus drivers.