Hyperviscosity syndrome associated with systemic plasmacytosis

Systemic plasmacytosis is characterized by plasma cell proliferation in multiple organs including skin, and by polyclonal hypergammaglobulinaemia. Hyperviscosity‐related retinopathy has never been described with this condition, to our knowledge. We report a case of systemic plasmacytosis in a 49‐year‐old Japanese woman, who presented with fever, multiple erythematous plaques, hypergammaglobulinaemia, renal failure and bilateral retinal haemorrhage. Reduction of immunoglobulin with oral steroid reversed the retinopathy related to hyperviscosity syndrome. When marked hypergammaglobulinaemia is found in a patient with systemic plasmacytosis, funduscopic examination should be performed to reveal early asymptomatic retinal changes, because the retinopathy is treatable by control of the underlying disease.