A rare case of oral mucosal blue-gray hyperpigmentation secondary to prerenal azotemia.

A 6 year-old-girl 4,5 years after liver transplatation due to biliary atresia  (a rare  congenital condition is characterised by totally absent bile ducts) is suffering from prerenal azotemia. She developed this condition due to dehydration by decreasing of the renal blood flow and reduction in glomerular filtration rate that results in accumulation of nitrogen-containing waste products in the blood plasma and most probably of beta-melanocyte-stimulating hormone, that increases melanin production.