Nail Abnormalities

Nail abnormalities occur in all age groups but are more prevalent in older adults. Nail disorders account for 10% of dermatologic disorders. Nail abnormalities can be categorized as surface texture irregularities, color changes, defects of nail plate attachment/nail shedding, tumors, or a combination of these. Brittle nails affect up to 20% of the population but are most prominent in older women and on fingernails. Different patterns of brittle nails can be seen in the same patient or can coexist in the same nail. Beau lines are transverse grooves caused by decreased keratinocyte activity in the proximal nail matrix. Nail pitting is due to abnormal keratinization in the proximal nail matrix. More than one-half of patients with psoriasis will have some nail involvement, and pitted nails are just one manifestation of nail psoriasis. Color changes may appear in the nail plate, nail bed, or nail matrix. In the nail unit, melanocytes are located only in the nail matrix. Brown-black nail changes are known as melanonychia and are caused by melanocyte activation or proliferation. Melanoma typically presents as longitudinal brown-black nail lines, but in approximately 30% of cases, it may present as a nail mass. Abnormal growth in the nail unit should raise concern for benign or malignant tumors, including the most common malignant tumor, squamous cell carcinoma. Nail clippings, ultrasonography, dermoscopy, and biopsy are useful for the diagnosis of nail abnormalities. Dermoscopy can assist in triaging lesions and differentiating those that can be safely observed from those that should be biopsied.