Psoriasis of the nail can lead to functional handicap as patients may have difficulty picking up objects because their nails are very thick and detach from their bed. Manual workers run the risk of further trauma to the nails. Contact with irritants and moisture also lead to the growth of fungus. The unsightly nature of psoriasis of the nail also causes patients distress, understandably as the hands, like the face, are very important in interpersonal relationships. Our hands allow us to communicate with other people and to touch them.

A study by the APLCP shows that significant discomfort is caused to patients by its impact on the ability to perform manual tasks and its unpleasant appearance. This impact is proportional to the site and extent of lesions. Patients usually do not like showing their hands and tend to hide them. The simple act of shaking someone's hand becomes problematic. People whose professions lead them into contact with the public find it difficult to tolerate people looking at their hands. For these reasons, psoriasis of the nail has a very profound impact on patient quality of life, and some people may be very insistent that the dermatologist finds a therapy to clear their lesions. Some patients say they are more upset by lesions on the nails (particularly of the hands) than lesions on other parts of the body.

There are superficial variants of psoriasis of the nail, where the nail may become slightly detached, and may or may not become discoloured. There are also more serious variants, where the nail becomes much thicker (hyperkeratosis) and becomes completely detached (onycholysis). Some more serious variants also affect the skin of the fingers. This is the case in dry acropulpitis, which causes lesions to the ends of the fingers and continual inflammation, or in acrodermatitis of Hallopeau (where lesions are pustular), which causes the nails to fall off definitively.

There is a scale for assessing the severity of psoriasis of the nail, called NAPSI, which is the equivalent of the PASI scale used for cutaneous lesions. NAPSI is used primarily during clinical trials. Psoriasis of the nail does not necessarily involve the nails of all fingers and toes, and sometimes, lesions can be present on one nail only. This means that it can be very difficult to assess the severity of lesions because nails are affected at different extents.

There are no truly effective treatments currently available for psoriasis of the nail. Patients need to be motivated as treatments take three to four months to show results. There is no visible improvement for the first two or three months of treatment as the nail takes two months to re-grow. The doctor should always check with the patient that the lesions were not caused by injury to the hand, wrist or nerves, as a Koebner response. It is also important that the patient does not scratch excessively. If necessary, the doctor should prescribe hand radiography to eliminate the possibility of arthritis.

As regards therapy, the doctor will sometimes recommend urea compounds to soften very thick nails and varnish to smooth them. Corticosteroid lotions or gels and vitamin A derivatives may also be used topically. In some cases, injecting cortisone into the nail matrix improves lesions, but this is often vary painful and increases the risk of infection. If several nails are affected and lesions are present in other parts of the body, the doctor will sometimes recommend systemic treatments, and vitamin A derivatives and methotrexate in particular. Treatments with flash lamps and excimer lasers are currently undergoing clinical trials. Finally, novel biologic therapies are used in exceptional cases for psoriasis of the nail.

Key points

Psoriasis of the nail may lead to functional difficulties and can be unsightly.

• It does not necessarily affect all fingers and toes. A single nail may be involved.
• There are no effective treatments currently available for psoriasis of the nail.
• However, a variety of topically and orally administered drugs are available.

Read more about psoriasis on the nails

* In Pso magazine, no.88, September 2005