ABSTRACT
Nail pigmentation may be caused by melanocyte activation or by benign or malignant melanocyte hyperplasia. Melanonychia can be the rst symptom of nail melanoma.
MELANOCYTE ACTIVATION
Melanonychia due to melanocyte activation is acquired, usually develops in adults and, in most cases, aects several nails. Causes of nail matrix melanocyte activation include dark phototype (racial melanonychia), drugs and
Box 28.1 Melanonychia
• Brown-to-black band of nail pigmentation • Melanocyte activation • Nevi • Lentigo • Melanoma
Box 28.2 Melanonychia due to Melanocyte Activation (Figures 28.1 through 28.3)
• Racial • Systemic disorders • Trauma • Drugs • Inammatory nail disorders • Nonmelanocytic tumors • Dermoscopy: Light-to-dark gray bands and
thin, gray, regular, longitudinal parallel lines
Figure 28.1 (a, b) Racial melanonychia: the bands are gray in color.
