A patient in renal failure may develop deposits over the skin surface termed uremic frost. Today it is rarely seen in developed countries because dialysis is readily available.
Clinical features:
(1) The patient has renal failure and an extremely high serum urea nitrogen (SUN, BUN), often over 200 mg/dL.
(2) The skin shows deposits of a friable, whitish or yellowish, crystalline material over the face, neck and chest that are crystals of urea and other nitrogenous compounds.
(3) Exclusion of other causes such as salt crystals.
The crystals can be collected and dissolved in deionized water, then analyzed for BUN.
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