Cold case: COVID-19-triggered type 1 cryoglobulinemia

Abstract A 42-year-old male was referred to the internal medicine department because of renal failure and persistent malaise after a recent SARS-CoV-2 infection. Blood results showed anemia and severe renal insufficiency (hemoglobin of 6.4 mmol/l and a creatinine of 194 umol/l). Additional tests revealed a type I cryoglobulinemia with a cryoprecipitate composed of biclonal IgM (kappa and lambda). Further investigations on the cryoprecipitate revealed that the immunoglobulins were directed against SARS-CoV-2 antigens. In the meanwhile, our patient noticed improvement of his symptoms accompanied by resolution of laboratory abnormalities. Three months later, the cryoglobulin could no longer be detected. Type 1 cryoglobulinemia is usually associated with lymphoproliferative disorders and is characterized by various symptoms caused by cryoprecipitates occluding small blood vessels. This is, to our knowledge, the first case of type I cryoglobulinemia with proven precipitation of SARS-CoV-19 antibodies. COVID-19 induced cryoglobulinemia appears to have a mild disease course and to be self-limiting upon viral clearance.