Recent upper respiratory tract infection and pityriasis rosea: a case-control study of 249 matched pairs.

A sample of 249 patients was drawn from an original population of 939 patients with pityriasis rosea identified in an earlier population-based study of pityriasis rosea in Rochester, Minnesota. A control was selected for each case, matched for age, sex, and year of diagnosis. Comparison was made with regard to recent immunization, history of atopy, and recent infection. A statistically significant number of patients had experienced recent upper respiratory tract infection (P less than 0.005). The association between recent infection and pityriasis rosea is discussed.