A decrease of blood flow to the distal toes regularly results in the development of nail dystrophy. The nail changes found in these circumstances are nearly identical with those seen in onychomycosis; the two diseases can be correctly identified only when potassium hydroxide (KOH) preparations and fungal cultures are carried out. Arteriosclerotic dystrophy is seen only in the toenails, fingernails are not affected. There is no effective treatment for these changes.

Beau's Grooves

Beau's grooves are depressions about 1 mm wide in the nail plate. These grooves extend horizontally from one lateral nail groove to the other. All nails are simultaneously affected. The depression occurs as the result of decreased nail protein synthesis during an episode of major physiologic stress.

Beau's grooves most commonly follow dramatic illnesses, such as myocardial infarction, or periods of high fever. Similar grooving also occurs after isolated periods of severe malnutrition. These grooves develop as the nail plate is forming in the nail matrix, but because of the slowness with which the nail plate grows, the grooves first become visible at the posterior nail folds several weeks after the original insult. The groove then remains in the nail plate, slowly moving distally during the several months it takes for the nail plate to renew itself completely.

Clubbing

Clubbing of the distal fingers is identified by the following three criteria: (1) flattening of the angle formed by the junction of the proximal nail plate and the paronychial fold, (2) rounding of the nail plate such that the distal edge curves slightly around the distal tip of the digit, and (3) widening or thickening of the digit from the distal interphalangeal joint to the tip. Clubbing is most commonly seen with chronic pulmonary or cardiopulmonary disease but also occurs with some tumors, especially those of the lung parenchyma. A somewhat similar process occurs in the thyroid acropathy of Graves' disease.

Nail Splitting

Splitting of the nail plate can occur in either of two forms: cracks oriented parallel to the length of the finger or separation of the nail plate layers such that "flakes" of nail chip off the distal edge. Some instances of splitting occur as the result of scar formation within the nail matrix, but most are idiopathic. Splitting generally worsens with aging.

Easy chipping (lamellar separation) of the nail plate is apparently due to excess drying of the nail. Some improvement is possible with frequent, long-term applications of lubricants containing humectants . The ingestion of gelatin, calcium, or vitamins is commonly recommended for the treatment of nail splitting, but proof of efficacy is lacking. Cosmetic improvement can be obtained by applying multiple layers of clear fingernail polish, such that the fissures or flakes are cemented together. False fingernails can also be cemented over the underlying dystrophic nail.

Warts

Periungual warts often distort the nail plate. In most instances the dystrophy is not permanent, and the nail plate returns to normal following therapeutic or spontaneous resolution of the warts. Permanent nail dystrophy occasionally occurs when warts have been present for long periods of time or when they have been aggressively treated with destructive modalities.