Pityriasis rosea Gibert: detection of Legionella micdadei antibodies in patients.

Some epidemiological and clinical characteristics of Pityriasis rosea Gibert has led us to hypothesize that this disease may be the clinical manifestation of an infection caused by legionellas. We have thus tested the sera of 36 patients ill with Pityriasis rosea and 19 controls for Legionella pneumophila serogroup 1-6 and Legionella micdadei antibodies. These, who had the same age and sex distribution as study patients, were receiving treatment for other diseases in the same ward. Also tested were 200 sera from the voluntary blood donors from the same region as study patients. Legionella micdadei antibodies were detected in 12 (33.3%) Pityriasis rosea cases and in one (5.2%) control. They were significantly more common in Pityriasis rosea cases than in either controls or voluntary blood donor population. The findings to date encourage continued research into the causative relationship between the Legionella micddadei infection and the onset of Pityriasis rosea Gibert.