Trauma to the nail can lead to the development of a subungual
hematoma and subsequent brown-black pigmentation in the nail bed.
Chronic trauma or pressure on the toenails may also lead to similar
deposition of pigment following hemorrhage within the area. White
discoloration (leuconychia) is common. It may be due to changes
in the nail plate (true leukonychia) or changes in the underlying
nail bed (apparent leukonychia). Transverse or punctate white areas
are usually a result of trauma, but may be familial. Half-and-half
nails (Lindsey nails) consist of white discoloration of the proximal
nail and red coloration of the distal portion, and are seen with
uremia. Terry nails, with white discoloration of all but a few millimeters
of the distal edge, are associated with cirrhosis or congestive
heart failure (eFig. 366.14). Paired horizontal
white bands, or Muehrcke lines, are seen with hypoalbuminemia and
chemotherapy, whereas Mee lines, transverse 1- to 2-mm white bands,
are due to arsenic, thallium, or lead poisoning. Longitudinal brown
or black pigmented bands (melanonychia striataor longitudinal melanonychia)
may indicate the presence of a melanocytic nevus or lentigo in the
nail matrix (eFig. 366.15). Such bands are
common in darkly pigmented races, but unusual in whites. Melanonychia
occurs more frequently on the fingers than on toes, with the thumb
most commonly affected. A solitary pigmented band that suddenly
changes in color or becomes wider may warrant a nail matrix biopsy
to exclude melanoma, even in an Asian or black individual.10 Extension
of the pigment over the proximal nail fold (Hutchinson sign) is
also suspicious for melanoma. Pigmented nail bands may also be seen
in Addison disease, Laugier-Hunziker syndrome, HIV infection, and
with medications such as chemotherapeutic agents and zidovudine.
When associated with oral melanotic macules and intestinal polyps,
Peutz-Jeghers syndrome is the likely diagnosis.