Membranous Nephropathy and Intrarenal Extramedullary Hematopoiesis in a Patient With Myelofibrosis.

Kidney disease in the setting of a hematologic malignancy is common, with the frequency and type of kidney disease varying depending on the specific malignancy. Various glomerular diseases and tumor infiltration of the kidneys have been reported in patients with lymphoproliferative disorders. Descriptions of kidney involvement in myeloproliferative disorders have been much rarer. We report a case of membranous nephropathy accompanied by kidney injury in a patient with primary myelofibrosis with additional features considered related to the patient's myeloproliferative disorder. A 63-year-old patient with primary myelofibrosis underwent kidney biopsy to investigate nephrotic-range proteinuria and reduced kidney function. Histologic analysis revealed mesangial sclerosis and hypercellularity, changes indicative of membranous nephropathy, and infiltration of hematopoietic cells into the renal interstitium, peritubular capillaries, and perirenal tissue consistent with extramedullary hematopoiesis. He was treated with renin-angiotensin blockade and a Janus kinase inhibitor, resulting in improvement in kidney function and proteinuria.