Almost everyone is familiar with the skin manifestations of psoriasis: reddened, plaque-like areas—often topped with a silvery scale—that occur on the knees, elbows, scalp, and elsewhere on the body.
Psoriasis is an autoimmune disease that can be triggered by skin injury, infection, certain medications, and by other unknown environmental factors. (The Merck Manual, 18th Edition. 2006:965-969)
Psoriasis affects approximately 5% of the population worldwide; up to 30% of persons affected develop a distinctive form of arthritis. Psoriatic arthritis is a chronic, inflammatory form of arthritis; although it often responds to treatment, it can cause significant joint destruction, pain, and crippling deformity.
Risk Factors for Psoriasis (and Psoriatic Arthritis)
- Anyone with psoriasis is at risk for developing psoriatic arthritis.
- Family history: At least 30% of people with psoriasis have a first-degree relative with this condition.
- Genetic makeup: The HLA-B27 genotype is associated with a higher incidence of psoriasis.
- Medications: Lithium, beta-blockers,chloroquine, ACE inhibitors, indomethacin and other nonsteroidal anti-inflammatories, terbinafine, interferon, and withdrawal from oral corticosteroids.
- Psychological stress: While there seems to be a connection between emotional stress and psoriasis, clinical evidence of such a relationship is lacking. (Picardi A, Abeni D. Stressful life events and skin diseases: disentangling evidence from myth. Psychother Psychosom 2001;70:118-36)
- Skin injury: Trauma, sunburn, etc.
- Systemic infection: HIV, streptococcus, etc.
(From Luba K, Stulberg D. Chronic plaque psoriasis. Am Fam Physician 2006;73:636-44)
Signs and Symptoms of Psoriatic Arthritis
- Symmetric or asymmetric joint inflammation in any person with co-existing psoriasis. Joint inflammation can precede or follow the development of skin lesions, and the severity of skin involvement is not a reliable predictor of who will develop arthritis or how severe it will be.
- Pain, redness, and swelling in large and small joints; the distal interphalangeal joints of the fingers and toes are particularly prone to involvement
- Morning stiffness of joints
- Back pain
- Sacroiliac pain
- Waxing and waning of joint inflammation that mirrors worsening and improvement of skin lesions
- X-ray evidence of resorption of terminal phalanges (tips of fingers and toes) and destruction and dislocation of both large and small joints (arthritis mutilans)
Treatment of Psoriatic Arthritis
- Drugs used for psoriatic arthritis are similar to those used for rheumatoid arthritis:
- Methotrexate
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Cyclosporine
- Gold therapy
- Tumor necrosis factor inhibitors and other biologic therapies (Note: Raptiva was recently withdrawn from the US market due to potentially fatal side effects)
- Long-wave ultraviolet-A phototherapy in conjunction with oral psoralens (PUVA therapy) has shown benefit for peripheral arthritis, but not for spinal involvement
- Patients with arthritis mutilans may require occupational and physical therapy
Psoriasis is a relatively common condition. Among those who suffer from this skin disease, up to one-third will also develop significant joint inflammation. Treatment of psoriatic arthritis leads to remission more frequently than in rheumatoid arthritis, but progression to arthritis mutilans and crippling may also occur.
Early recognition and treatment of psoriatic arthritis is the best means of preserving joint function.
