In a video on the "Keeping up with the Kardashians" website, star Kim Kardashian reveals she has psoriasis. In Kardashians: Don't be rash, Kardashian talks with dermatologist Dr. Harold Lancer about the "rash" on her body, which, her sister Khloe Kardashian, says is ringworm. Dr. Lancer examines the spots on her legs and tells Kardashian she has psoriasis—a chronic, genetic disease of the immune system that appears on the skin, often as red, scaly patches that itch and bleed.

Psoriasis is often misdiagnosed as a rash, ringworm or other skin irritation, such as eczema. However, psoriasis is the most common autoimmune disease in the country, affecting as many as 7.5 million Americans, including Kim Kardashian. Psoriasis occurs when the immune system sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious.

Like many celebrities with psoriasis, Kardashian is shocked and worried about the diagnosis because she faces so much scrutiny about her appearance. She even asks Dr. Lancer if it will appear on her face. Psoriasis most commonly occurs on the scalp, knees, elbows and torso, but it can develop anywhere. It very infrequently appears on the face.

"I'd heard of psoriasis before because my mom has always had it, but she didn't have red flaky dots all over her," says Kim, 30, about her psoriasis. There are five types of psoriasis: plaque, guttate, inverse, pustular and erythrodermic. Nearly 80 percent of people with the disease have plaque psoriasis—the most common form—which appears as red, raised patches.

Mom Kris Jenner was also diagnosed with psoriasis at age 30. The disease most frequently occurs between the ages of 15 and 35, but can appear at any time. While the exact cause of psoriasis is unknown, it is known that genetics and the immune system play a large role in developing the disease.

Kim appears equally shocked to learn there is no cure for psoriasis. Although the disease cannot be cured, a variety of treatments ranging from topical (on the skin) to systemic (throughout the body) can clear psoriasis, often for long periods of time.

Like millions of other Americans with psoriasis, Kim Kardashian is at increased risk for other serious health conditions associated with the disease, including heart disease, heart attack, diabetes, high blood pressure, obesity and depression. Up to 30 percent of people with psoriasis develop psoriatic arthritis, which causes painful swelling of the joints.

Dr. Lancer recommends that Kardashian try slowing down her lifestyle, as stress is a known trigger of psoriasis. Other triggers include external lifestyle factors, certain medications and injury to the skin, such as a cut or scrape. However, what triggers one person's psoriasis may not make it appear on someone else.