Psoriasis: Overview and Risk Factors

Psoriasis is a chronic disorder involving excessive production of skin cells. It affects more than 5 million Americans and nearly 80 million people worldwide.
Normally, skin cells are lost and replaced within about 27 days. In patients with psoriasis, the life cycle lasts only four days. As a result, patients may have abnormal thick, patchy skin. The cause of psoriasis is multifactorial, involving genetics, inflammation, and immune dysfunction.

Plaque psoriasis (also known as psoriasis vulgaris) is the most common form, accounting for 80 percent of cases. It is marked by symmetrically distributed skin patches and scales that occur primarily on the elbows, knees, scalp, and lower back, and may be painful or disfiguring. In addition, nail changes, including discoloration and thickening, occur in 50 to 80 percent of cases.

In most cases, the symptoms come and go over time and may be related to medications, trauma, stress, alcohol, or tobacco use. In severe cases, lesions cover more than 10 percent of the body and can have a significant effect on self-esteem and quality of life, sometimes contributing to depression and suicidal thoughts. More severe symptoms, including psoriatic arthritis, occur in 10 to 25 percent of patients, sometimes resulting in permanent joint damage if left untreated.

Risk Factors

Psoriasis can occur at any age, although most cases begin between the ages of 20 and 40. All races are affected, but the disorder is less common in African-Americans. Other factors associated with risk follow:

• Genetics: There is a clear genetic predisposition. Nearly half of psoriasis patients have an affected first-degree relative.
• Medication: Medications known to exacerbate symptoms include lithium, malaria antibiotics, beta-blockers, ACE inhibitors, and nonsteroidal anti-inflammatory drugs (e.g., ibuprofen).
• Steroid therapy withdrawal: Abrupt ending of steroid therapy (e.g., prednisone) can result in the sudden worsening of psoriasis.
• Infection: People with HIV and children with recurring infections, particularly streptococcal pharyngitis ("strep throat"), are at increased risk.
• Stress: Emotional and physiologic stress (trauma) has been linked to exacerbations, which may occur up to a month after the stressful event.
• Obesity: See Nutritional Considerations.
• Climate: Moderate amounts of sunlight can improve psoriasis. However, excessive sun exposure can trigger or exacerbate the disease.
• Alcohol intake and tobacco use are also important risk factors.