It typically involves painful inflammation of the joints and surrounding connective tissue, and can occur in any joint, but most commonly affects the joints of the fingers and toes. This can result in a sausage-shaped swelling of the fingers and toes known as dactylitis. Psoriatic arthritis can also affect the hips, knees, spine (spondylitis), and sacroiliac joint (sacroiliitis). About 30% of individuals with psoriasis will develop psoriatic arthritis. Skin manifestations of psoriasis tend to occur before arthritic manifestations in about 75% of cases. Nail changes
Psoriasis can affect the nails and produces a variety of changes in the appearance of fingers and toenails. Nail psoriasis occurs in 40–45% of people with psoriasis affecting the skin, and has a lifetime incidence of 80–90% in those with psoriatic arthritis. These changes include pitting of the nails (pinhead-sized depressions in the nail is seen in 70% with nail psoriasis), whitening of the nail, small areas of bleeding from capillaries under the nail, yellow-reddish discoloration of the nails known as the oil drop or salmon spots, dryness, thickening of the skin under the nail (subungual hyperkeratosis), loosening and separation of the nail (onycholysis), and crumbling of the nail. Medical signs
In addition to the appearance and distribution of the rash, specific medical signs may be used by medical practitioners to assist with diagnosis. These may include Auspitzs sign (pinpoint bleeding when scale is removed), Koebner phenomenon (psoriatic skin lesions induced by trauma to the skin), and itching and pain localized to papules and plaques.
Photographs of the scalp may be useful in monitoring the course of the disease and response to treatment. Causes
The cause of the various cicatricial alopecias is poorly understood. However, all cicatricial alopecias involve inflammation directed at the upper part of the hair follicle where the stem cells and sebaceous gland (oil gland) are located. If the stem cells and sebaceous gland are destroyed, there is then no possibility for regeneration of the hair follicle, and permanent hair loss results. Cicatricial alopecias are not contagious. In general, cicatricial alopecias are not associated with other illnesses, and usually occur in otherwise healthy men and women. Cicatricial alopecias affect both men and women, most commonly adults, although all ages may be affected. Epidemiologic studies have not been performed to determine the incidence of cicatricial alopecias. In general, they are not common. The majority of patients with cicatricial alopecia have no family history of a similar condition. The one exception is Central centrifugal cicatricial alopecia, which primarily affects women of African ancestry and may occur in several women in the same family. While it is possible to have more than one type of hair loss condition, non-scarring forms of hair loss do not turn into scarring forms of hair loss. Diagnosis
A scalp biopsy is essential for the diagnosis of cicatricial alopecia and is the necessary first step, as it can be hard to know the diagnosis for sure without a biopsy.