Localized peripheral calcium oxalate crystal deposition caused by Aspergillus niger infection.

A 70-year-old white man, who was malnourished and demented, presented with a painful black, gangrenous-appearing right foot with a fungating mass and required amputation. Pathological sections of the tissue specimens showed numerous birefringent crystals, which were identified as calcium oxalate. Branching septate hyphae and darkly pigmented fungal fruiting heads with double sterigmata characteristic of Aspergillus niger were also identified in the tissue sections. No systemic or other metabolic causes of oxalosis were found. The calcium oxalate crystal deposition was felt to be secondary to Aspergillus niger infection.