[1652] Renal Extramedullary Hematopoiesis Mimicking Tubulointerstitial Nephritis

Mariam P Alexander, Samih H Nasr, Paul J Kurtin, Mary E Fidler, Lynn D Cornell. Mayo Clinic, Rochester, MN

Background: Extramedullary hematopoiesis (EMH) is the presence and growth of hematopoietic tissue outside of the bone marrow, usually involving the liver and spleen. EMH of the kidney has rarely been reported. This is the first series outlining the clinicopathologic spectrum of intrarenal EMH.
Design: Patients (pts) with EMH in the kidney were identified from a biopsy database. Presenting clinical and laboratory findings and treatment and follow-up data were obtained. Pathology material was reviewed.
Results: Eight pts with intrarenal EMH were identified. The mean age at presentation was 68 yr (range 47-87); males predominated (M:F=7:1). All pts presented with renal failure, 2 with acute renal failure. The mean serum creatinine (SCr) at biopsy was 3.3 mg/dl (range 1.3-7.3). Six pts had proteinuria, 3 with nephrotic-range proteinuria. All biopsies showed a diffuse interstitial infiltrate that included megakaryocytes, granulocyte precursors (including many eosinophils) and clustered erythroid precursors, highlighted by immunostains for CD61, myeloperoxidase and glycophorin A. Tubular injury was present, but tubulitis was absent or rare. Two biopsies showed extrarenal extension. Two biopsies were misdiagnosed as tubulointerstitial nephritis (TIN). Five biopsies showed concurrent glomerular disease: 1 with fibrillary glomerulonephritis (GN) alone, 1 with fibrillary GN and chronic thrombotic microangiopathy (TMA), 1 with diabetic glomerulosclerosis and chronic TMA, and 2 with focal segmental glomerulosclerosis.
All 8 pts had an underlying hematologic malignancy: 5, primary myelofibrosis; 2, an unclassifiable chronic myeloproliferative neoplasm (MPN); and 1, multiple myeloma (MM) with extensive bone marrow involvement. In 6 pts, the hematologic malignancy was diagnosed prior to renal biopsy by a mean of 78 mos (range 7-180); in 2 pts, renal EMH was the first manifestation of MPN or MM. Six pts also had EMH in the liver and/or spleen.
Clinical follow-up data were available in all pts, at a mean of 9.6 mos post-biopsy (range 1-23). Five pts were treated with hydroxyurea and/or other chemotherapy, 1 was treated with steroids, and treatment data were not available for 2 patients. The mean SCr at follow-up in 7 pts without end-stage renal disease (ESRD) was 1.8 mg/dl (range, 1.1-2.7). SCr improved in 2 pts to near-baseline; 5 had persistent renal dysfunction; and 1 progressed to ESRD within 3 mos.
Conclusions: EMH should be considered in the differential diagnosis of TIN, even in pts without a previously known hematologic malignancy. Intrarenal EMH may have associated glomerular disease. Treatment of the underlying malignancy may improve renal function.
Category: Kidney (does not include tumors)

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 281, Wednesday Afternoon


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