A case of mucormycosis caused by Rhizopus microsporus in a renal transplant patient.

A 54-year-old man who had been on the kidney donor register for 32 years received a kidney from a 9-year-old boy who had died of fulminant myocarditis. The post-operative course was poor, and hemodialysis was still needed after surgery. A kidney biopsy one hour after surgery showed a neutrophil-predominant inflammatory cell infiltrate localized to the peritubular capillaries (PTC) and acute tubular necrosis of the proximal tubule. Rhizopus species was detected in a perirenal white exudate taken 29 days postoperatively, and the transplanted kidney was removed on postoperative day 45. The removed kidney showed fungal collection formation localized in the arteries and endotheliitis and embolization of the arteries. Renal damage caused by mucormycosis due to Rhizopus microspores was diagnosed. Mucormycosis is a fungal infection with a strong vascular affinity that develops along the vascular wall but does not extend beyond it. The infection leads to arterial infarction and organ failure. This report presents a rare case in which mucormycosis, which had been nested within the peritubular capillaries of the donor kidney, proliferated under immunosuppressive treatment but did so only in the artery, leading to infarction of the kidney. Neutrophilic collections within the PTC on one hour biopsy may be helpful in the early diagnosis of fungal infections.