A Case of Malignancy-Associated Cryoglobulinemia
A 75-year-old male was referred to the nephrology service for evaluation of hematuria, proteinuria and an elevated serum creatinine. His past medical history was notable for type 2 diabetes mellitus.\nOn the initial assessment, he appeared unwell. He was hypertensive with pedal edema and had dipstick hematuria and proteinuria. His urinary protein leak approximated 2 g/day. His initial biochemical laboratory findings are summarized in table .\nHis antinuclear antibody was positive with a homogenous pattern and he was hypo-complementemic; however, his anti-double-stranded DNA was negative. Serum protein electrophoresis demonstrated a monoclonal IgG kappa band.\nA renal biopsy was performed, which demonstrated a diffuse endocapillary proliferative glomerulonephritis (fig. ). Capillary wall kappa, IgG, IgM and C3 were noted on immunofluorescence (fig. ) and there were scattered subendothelial electron-dense immune-type deposits on electron microscopy. There was a florid intimal arteritis involving the interlobular caliber arteries. Several arterioles contained eosinophilic material within the vessel wall consistent with cryoprecipitates.\nRemarkably, coincidental sampling of perinephric fat demonstrated infiltration by a monomorphic population of CD20-positive B lymphocytes, which was suggestive of a low-grade B cell lymphoma (fig. ).\nThe suspected diagnosis was type 1 cryoglobulinemia due to an underlying lymphopro-liferative disorder. Computed tomography of the thorax, abdomen and pelvis revealed moderate hepatosplenomegaly and enlarged lymph nodes in the anterior mediastinum. However, an initial attempt did not confirm the presence of serum cryoglobulin. Due to the strong histological evidence and supportive clinical, radiological and laboratory findings, further sampling was performed and, this time, was positive. A subsequent bone marrow trephine biopsy was consistent with a diagnosis of low-grade follicular B cell lymphoma.\nThe patient's initial clinical course was complicated by a nosocomial pneumonia and respiratory failure. Following stabilization, the patient underwent combination chemotherapy (rituximab, cyclophosphamide, vincristine and prednisolone).\nThree months after initiation of therapy, the patient was normotensive and euvolemic, without constitutional symptoms. His follow-up laboratory findings can be seen in table .