Acne is a chronic inflammatory disorder of the pilose baceous follicles with a multifactorial aetiology. Androgen- induced seborrhoea, follicular hyperkeratinization, and the commensal bacterium Propionibacterium acnes

Propionibacterium acnes is often discussed as a contri­ buting pathogenic factor in the aetiology of acne lesions. The aim of this study was to test which porphyrin pat­ terns are synthesized by P. acnes in vivo in untreated acne patients and during standard acne regimens. These photosensitive compounds are potential targets for photo­ dynamic therapy of acne and need to be better characte­ rized in the skin. Using high­performance liquid chro­ matography coproporphyrin III was the main porphyrin identified in all patients. Coproporphyrin I and proto­ porphyrin were found at considerably lower concentra­ tions. When the porphyrin concentration of individual patients receiving isotretinoin was analysed repeatedly over time, clinical improvement was associated with lo­ wered levels of porphyrins. Statistical analysis demon­ strated a significant reduction in the porphyrin fractions only in the isotretinoin group which was associated with clinical improvement 2 months after starting therapy.