LAUSR

A 2-year-old male with a history of refractory acute myeloid leukemia (AML) received a matched unrelated donor stem cell transplant with a preparative regimen of busulfan, fludarabine, and single fraction total body irradiation (2 Gy). He was started on acyclovir, pentamidine, and voriconazole prophylaxis. His immediate post-transplantation course was complicated by engraftment syndrome, hyperacute graft versus host disease (GvHD) of the skin, sinusoidal obstructive syndrome (SOS), thrombotic microangiopathy (TMA), and acute kidney injury (AKI) with a peak serum creatinine of 1.2 mg/ dL (Fig. 1). He was admitted to the intensive care unit and treated with eculizumab, defibrotide, and continuous renal replacement therapy (CRRT). His serum creatinine (0.6 mg/ dL) improved 2 months post-transplantation but remained above his pre-transplantation baseline (0.2 mg/dL). Four months post-transplantation, complications included enterococcus bacteremia, histoplasmosis, and recurrent pericardial effusion. These conditions were successfully treated with cefepime, liposomal amphotericin, and ibuprofen, respectively. His creatinine level remained stable. Seven months post-transplantation, while off all immunosuppression, he developed eosinophilia (absolute eosinophils peak 2500 k/cumm), tubular dysfunction (glycosuria and proteinuria) with increased serum creatinine (1.0 mg/dL). Eosinophilia resolved spontaneously; however, elevated creatinine persisted. Recurrent AML was not detected on bone marrow biopsy specimen flow cytometry. Infection was excluded by serum PCR testing and urine culture. Eight months posttransplantation, he developed blistering erythema. Sections of a skin biopsy specimen showed evidence of GvHD. He had persistent high serum creatinine (1.2 mg/dL) with normal urinalysis. Evaluation for TMA was unremarkable. A percutaneous needle biopsy of the kidney was performed. Tissue cores were examined by brightfield, widefield epifluorescent, and transmission electron microscopy using conventionally accepted techniques. Tissue sections of amply sampled glomeruli showed normal-sized nuclei and were absent of hypercellularity, basement membrane defects, and immune complex deposits. Vascular lumina of arteries, arterioles, and glomerular capillary loops were patent. Tubular atrophy and interstitial fibrosis were mild and accompanied by infiltrates of CD3-expressing T-lymphocytes (Fig. 2A, B). Renal tubule epithelial cells contained markedly enlarged nuclei (Fig. 3), especially in medullary tubules (Fig. 2A, B). Some cortical tubule epithelial cells showed granular and foamy cytoplasm (Fig. 2A) that correlated to ultrastructural whorls of multi-laminated lysosomal vacuoles resembling zebra bodies (Fig. 2C), * Carlos C. Becerril Romero [email protected]