I suffer from psoriasis, which appeared after a bout of strep throat when I was 18. I recently have had to take two courses of antibiotics to treat a persistent strep throat, and within a week of starting the first course, the psoriasis returned. It is worse now than ever before. Is there connection between the return of the psoriasis and the strep infection or the antibiotics?

Jean

Psoriasis is a relatively common skin condition that typically first appears in young adulthood. The disease is characterized by flat skin lesions called plaques that are red with a silver, scaly surface. The plaques can be anywhere on the body, but the most common sites are the scalp, elbows, knees and back. This disease is thought to be caused by the person's own immune system attacking the skin. There is also a genetic component to the disease, and a sizable proportion of patients have a relative with the disorder.
Psoriasis is chronic illness with flare-ups that vary in intensity. One form of the disease, called guttate psoriasis, causes the sudden appearance of multiple psoriatic lesions. Guttate psoriasis may appear as a sudden flare-up in someone with psoriasis or it may occur in a young person who had no history of psoriasis.

Multiple factors can worsen psoriasis or cause the guttate form. Many drugs have been implicated, but antibiotics would be unlikely to initiate the illness. One intriguing cause of guttate psoriasis or psoriatic flares is infection with Streptococcal bacteria, including strep throat or a strep skin infection. Guttate psoriasis may happen because strep bacteria can make a type of toxin known as a "superantigen." Superantigens are capable of activating many different aspects of the body's disease-fighting immune system, with widespread effects. (This mechanism is responsible for the toxic-shock syndrome associated with tampon use.) In the case of psoriasis, the strep toxin may activate immune cells in the skin, resulting in the multiple psoriasis skin lesions.

In your case, there are three possibilities. You could have recurrent strep throat that is resulting in psoriasis. If this is the truly case -- and to be sure requires that you've had throat cultures that were positive for strep -- then you could prevent future outbreaks by taking continuous low doses of penicillin. I would consider doing this only if your diagnoses of strep infection were proven by throat culture and if your psoriasis is more than a minor annoyance. Another possibility is that the two episodes of psoriasis were unrelated to strep throat. It could simply have been a coincidence. A third, and less likely, possibility is that the antibiotics triggered the episodes. That is easy to test: If you ever get strep throat again, ask your doctor to prescribe a different antibiotic.