Nail pigmentation (chromonychia) can affect the nail plate diffusely or in striated fashion. It can be caused by excess production of pigment (e. g., melanin) or by the deposition of various substances (e. g., copper, medications, occasionally hemosiderin).


Brown or black discoloration is seen in Addison disease, Peutz−Jeghers syndrome, Laugier−Hunziker syndrome, hyperthyroidism, hemochromatosis, Cushing disease, and vitamin B12 deficiency. Local application of, or contact with, silver nitrate, potassium permanganate, iodine, 5-fluorouracil, and nail hardeners, as well as the systemic administration of gold salts, arsenic, cytostatic agents, ACTH, and PUVA therapy can also discolor the nails. If only one nail is affected, or if a striated, brown discoloration (melanonychia striata) is seen, the physician must suspect malignant melanoma. Other causes of striated discoloration include melanocytic nevi, various medications (zidovudine, antimalarial agents), subungual tumors, radiation, and, rarely, carcinoma of the breast.


Blue-gray discoloration of the nails is seen after silver or chloroquine intake. Gray discoloration can also result from malaria or visceral leishmaniasis. In Wilson disease, the lunula, in particular, takes on a blue color.


Yellow nails may be due to jaundice, Cronkhite−Canada syndrome, or the use of tetracyclines, D-penicillamine, or lithium. Yellow discoloration of exogenous origin is seen in heavy smokers and after the topical application of picric acid and glutaraldehyde. Yellow nail syndrome consists of yellow fingernails and toenails in combination with lymphedema and pulmonary manifestations (chronic pleural effusion, bronchiectasis, bronchitis).

The nails appear green in local Pseudomonas infection.


White nails (leukonychia) may be familial; total white discoloration is to be distinguished from transverse striate white discoloration or partially whitened nails (e. g., Terry nails, with a normal distal edge, seen in hepatic cirrhosis). White nails can also be a manifestation of chronic infection (leprosy), tumors (Hodgkin disease), hypoalbuminemia, and uremia (“half-and-half nail”).