One of the most characteristic (but not pathognomonic) onychopathies seen in chronic renal failure. Although the exact pathogenesis is unclear, it is speculated that acidosis and an increase in toxic uremic substances occurring subsequent to sudden renal decompensation may stimulate melanin formation by nail matrix melanocytes. Clinically, nails have a proximal pale pink or dull white "ground glass appearance" that is sharply demarcated from a red, pink, or brown distal portion. This is seen in an estimated 20%-50% of chronic renal failure patients.