dermatologic disorders
Nail Deformities and Dystrophies
Melanonychia striata
Melanonychia striata are hyperpigmented bands that are longitudinal and extend from the proximal nail fold and cuticle to the free distal end of the nail plate. Pigmentation results from deposition of melanin by melanocytes in the nail matrix. Deposition of melanin is increased by melanocyte activation (increased production of melanin in the nail cells) or by melanocytic hyperplasia (increased production of melanocytes in the nail matrix). Melanocyte activation may be a normal physiologic variant in people with darker skin. This variant, often called ethnic melanonychia, requires no treatment. Other causes of melanocyte activation include trauma, pregnancy, Addison disease and other endocrine disorders, infections, postinflammatory hyperpigmentation, and the use of certain drugs, includingdoxorubicin, 5-fluorouracil,zidovudine, and psoralens. Melanocytic hyperplasia can be caused by benign conditions, such as nail matrix melanocytic nevus or nail lentigo, or by malignant melanoma. Factors more often associated with malignant melanoma of the nail matrix include new onset after middle age, presence of pigmentation on the dominant thumb or hallux, rapid growth or darkening, bandwidth > 3 mm, associated nail plate dystrophy, or Hutchinson sign (extension of hyperpigmentation onto the proximal and/or lateral nail fold). Rapid biopsy and treatment are essential in cases of suspected Treatment ( 