Diagnose This (July 9, 2018)

What is your diagnosis in this native kidney biopsy?

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The photomicrograph shows an arteriole with extensive intimal arteritis as well as surrounding glomeruli with a membranoproliferative pattern of injury. Intimal arteritis in a native kidney is a very unusual finding with a small differential diagnosis. While this finding can be seen in patients with intravascular hematopoietic malignancy or mimics can be seen in the setting of thrombotic microangiopathy or adjacent cortical infarct, this is most commonly seen in the setting of cryoglobulinemia which was true in this patient. By immunofluorescence this cryoglobulinemic glomerulonephritis showed IgG and IgM deposition and was consistent with a type II cryoglobulinemia. Clinically the patient had positive rheumatoid factor, decreased C4 and positive cryocrit which supported this diagnosis.