Psoriasis: Diagnosis and Treatment

Diagnosis

Psoriasis is usually diagnosed by the classic appearance and location of plaques. Laboratory tests are not available to confirm or exclude the diagnosis. In equivocal cases, skin biopsy may aid diagnosis.

Psoriatic arthritis—also known as distal arthritis, which primarily affects the distal interphalangeal joints—is diagnosed by history, physical examination, and exclusion of other arthritic disorders, such as rheumatoid arthritis, gout, and ankylosing spondylitis. It is one of three seronegative arthritic disorders and may affect joints symmetrically or asymmetrically.

Treatment

Despite a wide range of therapeutic options, psoriasis can be a challenge to treat. Treatments are based on the type of psoriasis, severity, and areas of skin affected.

Topical Therapies
Topical creams and ointments are the initial therapy for mild to moderate disease.

Topical corticosteroids are especially useful for widespread plaques and lesions that are resistant to other therapies. Low–potency steroids may be used on the face and intertriginous areas, whereas more potent steroids are reserved for the scalp and thick plaques on extensor surfaces. However, resistance to steroid creams can develop quickly, and withdrawal may cause exacerbation of disease. Long–term or excessive use can lead to thinning of skin, easy bruising, and systemic side effects.

Vitamin D analogues (eg, calcipotriene) slow keratinocyte growth, flatten lesions, and remove scale.

Anthralin has been used effectively for more than a century. It is believed to normalize DNA activity in skin cells.

Tazarotene, a retinoid, normalizes DNA activity in skin cells, but may cause skin irritation and is contraindicated in pregnant women, or those who may become pregnant.

Coal tar is probably the oldest known treatment and is used to reduce inflammation, itching, and scaling. Moisturizing creams and ointments can also reduce itching and scaling. However, lotions have the reverse effect. Medicated shampoos are used for scalp lesions.

Phototherapy is known to be beneficial and is used especially for generalized disease. Options include natural sunlight (lesions usually improve during the summer), psoralen plus ultraviolet A radiation (PUVA), and ultraviolet B radiation. Phototherapy may be combined with topical treatments to increase efficacy.

Systemic therapy may be required for severe or treatment–resistant psoriasis. Options include oral retinoids (acitretin), methotrexate with folic acid, azathioprine, cyclosporine, sulfasalazine, and hydroxyurea. These can have significant side effects and are contraindicated in pregnant women. Immune–modulating drugs (eg, alefacept, efalizumab, etanercept) are now being used for severe and refractory cases.

Psychological approaches may be valuable in individuals with psoriasis. Stress plays an important role in the onset, exacerbation, and prolongation of psoriasis,¹ and appears to impair the clearance of lesions in phototherapy–treated patients². Some evidence indicates that hypnosis1 and cognitive–behavioral stress management programs³ reduce symptom severity.