Psoriasis is a skin disease caused by problems with the immune system. It is characterized by sore or itchy patches of thick, red skin with silvery-gray scales that can appear nearly anywhere on the body, although they usually emerge on the knees, elbows, back, scalp, face, palms, and feet. While symptoms may come and go, the condition can last a very long time, even a lifetime.
Although skin cells that grow deep in the skin normally rise to the surface in a process called “cell turnover”, in those afflicted with psoriasis, the process takes only days, rather than months. Psoriasis affects approximately 1-3 percent of the world’s population, mostly adults.
And while it is known that stress, infections, dry skin, and certain medications can exacerbate the condition, the cause of psoriasis is not fully understood. It sometimes runs in families, suggesting a genetic association. Environmental factors and certain medications, however, continue to be suspected as at least contributing to its cause.
There are different types of psoriasis, including:
- Plaque psoriasis – by far the most common form
- Flexural psoriasis – occurs mostly in skin folds
- Guttate psoriasis – associated with streptococcal throat infection
- Pustular psoriasis – bumps filled with noninfectious pus
- Nail psoriasis – produces a variety of changes in the appearance of finger and toe nails
- Psoriatic arthritis
- Erythrodermic psoriasis – potentially fatal widespread inflammation and exfoliation of the skin
Drugs associated with the onset of psoriasis include:
- ACE inhibitors
- angiotensin receptor antagonists
- antimalarials
- beta-blockers
- bupropion
- calcium channel blockers (such as Cardizem)
- carbamazepine
- interferon (IFN) alfa
- lithium
- metformin
- NSAIDs
- Terbinafine
- Tetracyclines
- valproate sodium
- venlafaxine
Drugs that may aggravate existing psoriasis include:
- alcohol
- antimalarials
- beta-blockers
- lithium
- mepacrine
- NSAIDs
Initial treatment for psoriasis depends on its type, location, severity, and extent, and on the patient’s age, sex, lifestyle, co-morbidities, and risk tolerance. If topical agents (such as creams or ointments) or other medications are unsuccessful, phototherapy and then drugs with a greater risk for adverse reactions may be employed. Medications with a high potential for toxicity, however, are reserved for unresponsive or severe psoriasis. Phototherapy involves exposure of skin to ultraviolet (UV) radiation.
To prevent resistance to a specific treatment from developing (tachyphylaxis) and reduce the risk of adverse reactions, treatments may be periodically changed (treatment rotation).