It's been over a decade since we published the observation suggesting a possible role of Chlamydia pneumoniae in the etiology of acne rosacea. In that small patient series studied, the vast majority of subjects responded with moderate to marked improvement to a modified oral regimen of azithromycin. A significant number of the patients were identified with C. pneumoniae antigen in representative malar skin biopsies by immunoperoxidase technique using monoclonal antibody to C. pneumoniae. Nine

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... the 10 subjects received a modified regimen of azithromycin shown to be effective to treat acne rosacea. C. pneumoniae antigen was detected in malar biopsy specimens in 4 of 10 subjects by immunoperoxidase technique (using monoclonal antibody to C. pneumoniae. Serum antibodies against C. pneumoniae were detected in 8 of 10 intent-to-treat subjects. Using polymerase chain reaction, C. pneumoniae was not detected in peripheral blood mononuclear cells. The inflammatory response in tissues was characterized by a widespread infiltration of polymorphonuclear neutrophil cells, lymphocytes, and plasma cells, supporting the clinical diagnosis of acne rosacea. Nine of 10 subjects treated with azithromycin showed moderate to marked improvement of their acne rosacea. To our knowledge, this unique observation had not been reported elsewhere, and follow up studies including a study of the prevalence of antibodies to C. pneumoniae were never performed 1 . Based on the results of this small study, it was tempting to suggest the presence of Chlamydia in the skin lesions of rosacea patients and their clinical improvement with azithromycin, would offer support to the notion Chlamydia infections could serve as one of the causes of acne rosacea. Azithromycin has been widely used in the treatment of Chlamydia infections, and its efficacy in the treatment of rosacea had already been documented 2 . It was never our intent to suggest a cause and effect relationship based on our findings linking C. pneumoniae in some way to the etiology of rosacea. At the time our study was performed there was excitement in the medical community at large trying to link C. pneumoniae to a host of medical conditions, including heart disease and other disorders associated with vascular inflammation, and hyperreactivity. It was hoped our observation would trigger interest in pursuing this issue beyond the limitations intrinsic to the small number of patients we studied, and the nominal immunological parameters evaluated. Gazing back now, though there was little interest expressed by sources of financial support, and others to probe deeper into our findings, other observations about the possible etiology of rosacea began to appear.