Although psoriasis primarily is a skin condition, it also can affect fingernails and toenails as well. Nail psoriasis, or psoriatic nail disease, causes discolorations, deformations and other abnormalities in the nail and nail bed. In most cases, skin psoriasis, or cutaneous psoriasis, is present when nail psoriasis develops. Psoriatic arthritis often is accompanied by psoriatic nail disease as well.
The causes of nail psoriasis are not fully understood, but heredity does play a role. Environmental and immunologic factors also contribute to an individual’s likelihood of developing the condition. Psoriatic nail disease is not contagious, however, so it cannot be passed on through contact.
Nail psoriasis can be identified by a number of commonly observed markings and discolorations of the nail. Horizontal lines called "Beau’s lines" might be visible running side to side across the nail, or white spots called "leukonychia" might be visible. Discoloration of the nail is common, and oil spots or salmon patches, which appear to be drops of oil or blood trapped under the nail, also might be present. A splinter hemorrhage, where a tiny break in the skin cause a small bleed under the nail, might be visible as a thin black line running the length of the nail. Spotted lunula, a congestion of the capillaries under the nail, might appear as a reddening of the arch at the base of the nail.
Changes in the nail’s shape and structure also are common. Nail psoriasis commonly causes pitting. The skin under the nail might thicken and cause the nail to loosen and separate. When psoriasis affects the nail bed, crumbling of the nail might result. Exposed nail beds are more vulnerable to infection, further complicating the condition.
Approximately 5 percent of people with psoriatic nail disease have no visible signs of skin psoriasis. In these cases, a biopsy might be required to confirm the diagnosis. There is no cure for nail psoriasis. Medical treatment is focused on minimizing symptoms, improving the appearance and function of the nails and treating any complicating issues such as infection.
A doctor might prescribe topical creams and ointments to treat nail psoriasis. In some cases, the doctor might determine that the nail or a portion of the nail must be removed. This can be done with chemical treatment or through surgery.
Trimming back nails will reduce the chance of infection by helping to prevent them from catching and pulling away from the nail bed. Care for affected nails must be done gently. Overly aggressive grooming or nail care might cause the psoriasis to flare up and worsen the condition.