Other nail disorders

Brittle nails split horizontally, and break off easily. The cause is unknown, but repeated immersion in water may be a factor. Brittle nails are not caused by a vitamin deficiency or lack of calcium in the diet, and are not associated with systemic disease. Nail hardeners are not useful for brittle nails. Management of brittle nails involves:

• avoiding exposure to water, soaps and detergents as much as possible
• applying thick emollients containing urea 10 to 30%, two to three times daily.

Koilonychia (spoon nails) is common in young children and does not need treatment. In adults, most cases are idiopathic or are a result of trauma, but some are caused by iron deficiency anaemia.

A myxoid pseudocyst occurs when osteoarthritis in the distal interphalangeal joint is associated with myxoid fluid leakage into surrounding tissue. This fluid collects and forms a pseudocyst that exerts pressure on the dorsal surface of the nail matrix, causing a gutter-like depression in the nail plate—the most common site of the depression is the proximal (posterior) nail fold. Sometimes pseudocysts resolve spontaneously. If the pseudocyst persists and the patient is concerned, refer for specialist advice. Even after surgery, pseudocysts often recur.

Twenty nail dystrophy (also known as widespread ‘trachyonychia’ of all twenty nails) is characterised by a roughening of the nail surface, longitudinal ridging, pitting, and loss of lustre. This can result in brittle and distorted nails. The cause is unknown. Twenty nail dystrophy is most commonly associated with dermatitis, psoriasis, lichen planus and alopecia areata. The nail changes are most commonly seen in childhood, and tend to be self-limiting and improve with age.

Median canaliform dystrophy (also known as median canaliform dystrophy of Heller) is a characteristic change in the nail plate resulting in a midline longitudinal furrow with transverse ridges (a ‘fir-tree’ pattern). It is an acquired nail change associated with microtrauma of the nail matrix. The condition can occur at any age, and most commonly affects both thumbnails (but can also be unilateral). Diagnosis is clinical; further investigations may be required if a tumour of the nail matrix is suspected.

Subungual warts are treated as for common warts, but care needs to be taken when using liquid nitrogen cryotherapy to avoid damage to the nail plate.