Longitudinal melanonychia

BACKGROUND. Ungual melanoma is the most serious disease affecting the nail. The majority start with a longitudinal brown streak in the nail. OBJECTIVE. To outline the different nail pigmentations, their differential diagnoses, treatment, and prognosis. METHOD. Clinical and histologic evaluation of dark nail pigmentations. CONCLUSION. Brown to black nail pigmentation may be due to different colori ng substances of exogenous and endogenous origin. Exogenous pigmentations u sually are not streaky or do not present as a stripe of even width with reg ular borders. Bacterial pigmentation, most commonly due to Pseudomonas aeru ginosa or Proteus spp., have a greenish or grayish hue and the discoloratio n is often confined to the lateral edge of the nail. Subungual hematoma may result from a single heavy trauma or repeated microtrauma which often esca pes notice. The latter is usually found on the medial aspect of the great t oe. Although oval in shape, it commonly does not form a neat streak. Melani n pigmentation in the form of a longitudinal streak in the nail is due to a pigment-producing focus of melanocytes in the matrix. Neither the color in tensity nor the age of the patient are proof of benignity or malignancy alt hough subungual melanomas are very rare in children and malignant longitudi nal melanonychia is usually wider than 5 mm. Hutchinson's melanotic whitlow , nail dystrophy, and a bleeding mass strongly suggest malignancy. Treatmen t is as conservative as possible in order to keep the tip of the digit; onc e the melanoma is completely removed, amputations have nor been shown to pr olong the disease-free survival time.