Argyria.

The distinctive blue-gray discoloration that occurs in argyria is due to deposition of silver and a silver-induced increase in melanin. Argyria is pronounced in areas of sun exposure and in the lunulae of the fingernails. Skin biopsy confirms the diagnosis by demonstrating tiny brownish granules in connective tissue surrounding sebaceous glands, in perineural tissue and in arteriolar walls. Pigmentation is permanent but benign. While the incidence of argyria is declining, its recognition remains important.