IgA multiple myeloma presenting as Henoch‐Schönlein purpura/polyarteritis nodosa overlap syndrome

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Abstract
We report the unusual case of a man with a 5‐year history of relapsing Henoch‐Schönlein purpura (HSP) and macroscopic polyarteritis nodosa (PAN) as early manifestations of IgAκ multiple myeloma. The glomeruli contained monoclonal IgAκ deposits, without other immunoglobulins or λ light chains. Glomerular deposits lacked the usual electron density but could be demonstrated by immunoelectron microscopy. Multisystem large vessel vasculitis (antineutrophil cytoplasmic antibody negative) produced aneurysms of renal and hepatic arteries, whereas small vessel vasculitis affected the skin and glomeruli, producing a symptom complex of HSP with dermal and glomerular deposits of IgA. We conclude that HSP/overlap syndrome may be the initial manifestation of IgA myeloma and should be considered within the spectrum of monoclonal IgA deposition disease.