Background: A 59-year-old man who had undergone a left nephrectomy for renal cell carcinoma was found to have metastatic disease during a restaging examination. The patient was started on treatment with interferon alpha2b plus bevacizumab, a humanized monoclonal anti-vascular endothelial growth factor antibody. After 9 months of this therapy, the patient developed proteinuria, which gradually increased to over 6 g/day.
Investigations: Physical examination, urine and blood analysis, biopsy of the right kidney, and histologic evaluation of the non-neoplastic portion of the left nephrectomy specimen.
Diagnosis: Thrombotic microangiopathy and IgA immune-complex deposition in the glomerular capillary walls and mesangium.
Management: Discontinuation of interferon alpha2b and bevacizumab, control of blood pressure with an angiotensin-converting-enzyme inhibitor and an angiotensin-receptor blocker.