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Sjogren Syndrome — SCE Rheumatology MCQ

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HardConnective Tissue DiseaseSjogren SyndromeSCE Rheumatology

A 54-year-old woman with Sjögren disease develops recurrent palpable purpura over both lower legs, fatigue and a painful sensorimotor peripheral neuropathy. Serum C4 is low and rheumatoid factor is positive. Immunofixation of the serum cryoprecipitate demonstrates monoclonal IgM-kappa together with polyclonal IgG. Which pathological process best accounts for these findings?

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Correct answer: B — Monoclonal IgM rheumatoid-factor complexes causing type II cryoglobulinaemic vasculitis

This is type II cryoglobulinaemic vasculitis. Its cryoglobulin consists of monoclonal IgM, usually IgM-kappa, with rheumatoid-factor activity directed against polyclonal IgG. The resulting cryoprecipitable immune complexes activate complement and produce small-vessel inflammation, explaining palpable purpura, neuropathy and disproportionate C4 consumption. Type I cryoglobulinaemia contains a single monoclonal immunoglobulin and more often causes occlusive manifestations such as hyperviscosity, digital ischaemia or necrosis. IgA vasculitis requires IgA-dominant vascular deposition and is not explained by the specified IgM-IgG cryoprecipitate. Thrombocytopenia causes non-palpable bleeding without this complement-consuming neuropathic syndrome. A drug reaction is unsupported by the immunofixation findings. Type III mixed cryoglobulinaemia would contain polyclonal, rather than monoclonal, IgM.

Reference: Zignego AL et al. Cryoglobulinemia: An update on classification, pathophysiology, clinical presentation, and management. Journal of Internal Medicine. 2026;299(2):196-215. https://pubmed.ncbi.nlm.nih.gov/41298332/