A 55-year-old patient had chronic renal failure and pigmentary nail changes. The distal nail appeared dark brown while the proximal nail was white. This nail pattern has been previously called the ``half-and-half nail" and is believed to be a nail pattern uniquely found in certain patients with chronic renal failure. A biopsy showed the pigment to be melanin. Stimulation of matrix melanocytes during sudden renal decompensation is proposed as the cause of this nail finding.
Leyden JJ, Wood MG. The ``Half-and-Half Nail"A Uremic Onychopathy. Arch Dermatol. 1972;105(4):591-592. doi:10.1001/archderm.1972.01620070063024