IgG4-RD vs Sjögren — RACP Adult Medicine MCQ

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HardRheumatologyIgG4-RD vs SjögrenRACP Adult Medicine

A 30-year-old man presents with bilateral parotid swelling, xerostomia, and keratoconjunctivitis sicca. He has elevated IgG4 and bilateral lacrimal gland enlargement. Biopsy shows dense lymphoplasmacytic infiltrate with IgG4+ plasma cells >40 per HPF and storiform fibrosis. What is the diagnosis?

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Correct answer: C — Lymphoma

While the presentation mimics Sjögren syndrome (bilateral parotid/lacrimal swelling, sicca symptoms), the markedly elevated IgG4 with characteristic histological features (storiform fibrosis, dense lymphoplasmacytic infiltrate with IgG4+ cells >40/HPF, IgG4:IgG ratio >40%) is diagnostic of IgG4-related disease (specifically IgG4-related sialadenitis and dacryoadenitis – formerly Mikulicz disease). Unlike Sjögren, anti-Ro/La antibodies are typically negative. Treatment with corticosteroids produces excellent response. Rituximab is used for relapsing disease.

Reference: eTG – 2025 – Rheumatology; ACG – 2024 – IgG4-Related Disease Guidelines