Fibrillary comma-shaped electron-dense organized glomerular deposits associated with cryoglobulinaemia.

Abstract

A 51-year-old caucasian lady was hospitalized because of purpuric papules of the lower extremities, myalgias, arthralgias, haematuria and proteinuria. Her blood pressure and renal function were normal. She had a history of cerebrovascular accidents, and a previous nuclear magnetic resonance showed three ischaemic lesions. Laboratory work-up including liver function, hepatitis B surface antigen, hepatitis C antibody, immunoglobulins (Igs), antinuclear antibody, antineutrophil cytoplasmic antibody, rheumatoid factor, antistreptolysin O titre and antiphospholipid antibodies was normal or undetectable. No monoclonal immunoglobulins were detected on analysing blood protein electrophoresis. In contrast, C3 was mildly diminished while C4 was significantly diminished. Urinary protein excretion was 1.2 g daily without Bence–Jones proteinuria. Mixed cryoglobulins were detected only once (cryocrit 0.5%). She underwent a renal biopsy. Light microscopic examination showed membranoproliferative glomerulonephritis (MPGN) with lobular accentuation. Congo red staining was negative, and immunofluorescence microscopic studies demonstrated positive staining for IgG, IgM, IgA (at lower intensity than the other Igs) and C3 in the mesangium and glomerular capillaries. Ultrastructural examination evidenced mesangial, subendothelial and subepithelial organized electron-dense deposits (Figures 1 and 2) characterized by curved fibrils with a diameter of 24 nm. The curvilinear patterns of fibrils look like commas disorderly infiltrating glomerular structures. Cryoglobulinaemia type III was diagnosed. Two months later a uterine malignant neoplasm was discovered.