Two renal allograft biopsies with histologic features suspicious for recurrence of scleroderma. Note the prominent myxoid changes in the artery in biopsy (a) as well as the severe intimal thickening of blood vessels, which is accompanied by thrombosis and schistocytes within the arteriole wall in biopsy (b). The differential diagnosis includes acute antibody-mediated rejection and acute calcineurin inhibitor toxicity. Clinical correlation with the presence of C4d stain, detection of circulating donor-specific antibodies, and calcineurin inhibitor levels are usually warranted to achieve a correct diagnosis [(a) H&E; original magnification x200 and (b) Methenamine silver stain; original magnification x400].
