Diagnose This (July 16, 2018)

What is your diagnosis in this native kidney biopsy? And for bonus points, what do you suspect is the underlying etiology of the diagnosis?

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The images show acute tubular necrosis. While patterns of acute tubular injury are non-specific there are clues in this case to the etiology. First, the tubular injury is quite severe (acute tubular necrosis) with the tubules show focal areas of necrosis and denudation of the epithelium. Second, the tubular nuclei are exceptionally reactive to the point of showing bizarre nuclear features. And, in the high-powered image, an eosinophilic, intracytoplasmic inclusion is seen (represents mitochondrial abnormalities ultrastructurally). Taken together, these soft findings are concerning for tenofovir nephrotoxicity which fit this case as the patient did have HIV and was on a combination therapy containing tenofovir. Reference: Herlitz LC, et al. Tenofovir nephrotoxicity: acute tubular necrosis with distinctive clinical, pathological, and mitochondrial abnormalities. Kidney International (2010) 78, 1171–1177; doi:10.1038/ki.2010.318