Rare presentation of hypocomplementaemic urticarial vasculitis syndrome (HUVS) overlapping with systemic erythematosus lupus (SLE) and small lymphocytic lymphoma (SLL).

Hypocomplementaemic urticarial vasculitis syndrome (HUVS) is a rare immune complex-mediated disorder marked by non-pruritic urticarial lesions, hypocomplementaemia (low C1q levels), leucocytoclastic vasculitis and systemic manifestations (joint pain, angio-oedema and uveitis). Complications include renal disease, lung disease and acute laryngeal oedema that can prove fatal. Distinguishing HUVS from systemic lupus erythematosus (SLE) is challenging due to overlapping symptoms and diagnostic criteria. Here, we present the case of a male who presented with uveitis, maculopapular (and urticarial) rash and facial and joint swelling. Investigation revealed atypical antineutrophil cytoplasmic antibody, elevated antinuclear antibodies, low C1q and leucocytoclastic vasculitis on skin biopsy. Renal biopsy showed diffuse mesangial focal endocapillary proliferation with full-house immunofluorescence staining concerning for HUVS versus SLE class III nephritis. The management of HUVS is complicated by a lack of FDA-approved guidelines, with therapies ranging from non-steroidal anti-inflammatory drugs to immunosuppressants. The overlapping of HUVS, SLE and small lymphocytic lymphoma necessitates a collaborative multidisciplinary approach to control disease progression and improve outcomes.