DEAR DOCTOR K >> My doctor thinks my arthritis and heart disease are connected to my psoriasis. Is this possible? I thought psoriasis was a skin condition.
DEAR READER >> Psoriasis (pronounced so-RYE-uh-sis) is named for an ancient Greek word meaning an itchy or scaly condition. It is classified as a skin disease, but psoriasis is the result of an immune system abnormality that can cause problems throughout the body.
With psoriasis, white blood cells of the immune system become overactive. They produce excess amounts of chemicals that trigger inflammation. The inflammation leads to abnormally rapid growth of cells in the skin's outer layer. This causes plaques: raised, red patches covered with silvery scales on the elbows and knees — the classic sign of psoriasis.
But the effects of psoriasis are not always confined to the skin. The disease also can cause inflammation throughout the body. This probably is the reason that people with psoriasis have higher rates of various diseases that also are associated with a constant state of inflammation. These include diabetes, heart disease, high blood pressure and several types of cancer.
Nearly one-third of people with psoriasis develop psoriatic arthritis, which causes stiff, painful joints and other symptoms.
Several eye problems are more common with psoriasis, including conjunctivitis, blepharitis (inflammation of the eyelids) and damage to the cornea.
When psoriasis involves only the skin, it often can be treated just by medicines applied to the skin. Very mild cases of psoriasis may improve with moisturizers and some sunlight. But most people need other treatments:
• Ointments, gels or lotions. The most common are corticosteroids, which come in varying strengths. They quickly reduce inflammation and control itching. Long-term use of strong steroids can thin and damage skin.
• Phototherapy. This treatment uses carefully controlled exposure to ultraviolet (UV) light, which helps slow the growth of skin cells. UV light combined with medicines called psoralens often is more potent than just UV light (a treatment called PUVA).
• Systemic therapy. If your psoriasis has caused more than skin problems, this can have implications for the kind of treatment your doctor may recommend. Treatments that fight inflammation in multiple parts of the body may be required. Medicines that do this include methotrexate, retinoids and cyclosporine.
Exercise and weight loss, which help fight inflammation, may help. Adopting other healthy lifestyle choices, such as avoiding tobacco and eating well, can help prevent health problems linked to psoriasis.
Dr. Komaroff is a physician and professor at Harvard Medical School.