Pityriasis rosea rash often appears in spring and fall

Sure it's intellectually satisfying to hit on a diagnosis in a challenging medical case, just like those glamorous TV doctors. It's also nice once in a while to make a diagnosis just by walking into an exam room.

That's why I particularly enjoyed it when my partner asked me to stop in a room to check out a teenager's rash. I did, and had the 14-year-old lift his shirt to reveal an impressive number of large, scaly, slightly pink ovals covering his trunk.

I asked the teen if he recalled seeing one particular spot at the start of the illness, and he pointed out a larger lesion on his upper abdomen. "Ah," I nodded wisely, "that's the herald patch and what you have is pityriasis rosea."

I left the room, leaving the in-depth explanations to my partner, who already knew the diagnosis, but wanted to reassure the worried mother with two concurring medical opinions.

Yes, pityriasis is one of those cooperative diseases where patients might as well come to the office with the name of the disease stamped on their forehead. The rash looks like something out of a medieval textbook on the plague, but is actually a fairly common, relatively innocuous illness that some researchers blame on a yet-to-be-named virus.

Patients with pityriasis can participate in normal daily activities and may be around others while attending school and going to work. They'll want to wear a shirt to cover the lesions, which can be a bit scary for those who have to be near the rashy one.

According to experts at the American Academy of Dermatology, pityriasis tends to crop up in the spring and fall seasons, is most often seen in patients 10 to 35 years of age, and usually occurs only once in an individual's life.

The extensive trunk rash follows the appearance of the herald patch by a week or two. The rash may also involve the neck, arms and legs, and all of these lesions can hang around for up to six to eight weeks -- and several months in some cases.

Pityriasis rosea is self-limited, so patients will fix themselves without treatment. But remember, as with most body rashes, pityriasis can become more noticeable and sometimes itchier if the patient is overheated in a hot bath or exercises vigorously. Keep cool, when possible. Sometimes pityriasis can cause such uncomfortable itching that the child or teen will require the use of soothing body creams, topical steroids or oral antihistamines.

If you can't wait the expected number of weeks for the ugly rash to disappear -- think upcoming prom or graduation -- consider a visit with a dermatologist to discuss treatments such as ultraviolet light therapy or alternate oral medications.