Monoclonal Gammopathy of Renal and Neurological Significance Associated with Type 1 Cryoglobulinaemic Vasculitis: A Case Report

Monoclonal gammopathy of undetermined significance (MGUS) is a pre-malignant plasma cell dyscrasia characterised by abnormal paraprotein production without associated end-organ damage.When end-organ damage is present, the clinical syndrome is described in terms of the organ system affected such as monoclonal gammopathy of renal significance (MGRS).We present a case of monoclonal gammopathy of renal and neurological significance which manifested as a cryoglobulinaemic vasculitis driven anuric acute kidney injury and peripheral neuropathy, in a gentleman with a history of malignant melanoma.Kidney biopsy revealed characteristic cryoglobulinaemic glomerulonephritis and repeated cryoglobulin serological testing ultimately revealed an IgG cryoglobulin.The case was complicated by melanoma recurrence with brain metastases requiring initiation of immune checkpoint inhibitor therapy.This case highlights the challenges in diagnosis and treatment of monoclonal gammopathy with end-organ involvement in the setting of cryoglobulinaemic vasculitis driven by a plasma cell dyscrasia as well as managing a metastatic malignancy and therapies that regulate immune activation.