Background: The modulatory domain of the human androgen receptor (AR) gene contains a polymorphic CAG repeat coding for a polyglutamine tract which is inversely correlated with transcriptional activity of the AR. Androgens acting through the AR play a crucial role in the pathogenesis of acne vulgaris. We therefore investigated the relationship between CAG repeat polymorphism in the AR gene and acne susceptibility. Methods: 206 acne patients and 200 controls participated in the study. Genomic DNA was extracted from peripheral blood lymphocytes of individual patients, and the CAG repeat region was amplified by polymerase chain reaction (PCR) using fluorescence-labeled primers. Samples were then run on an ABI 377 gene scan analysis gel with an internal molecular-weight marker. Ten male samples were chosen randomly for sequencing to confirm the number of CAG repeats. The 2-sample independent t test was used to analyze the data. Results: The mean number of the CAG repeat in the AR was 22.07 (14-28) in the controls and 20.61 (13-26) in the male acne group. There was a significant correlation between the CAG repeat length and male acne. No significant difference was observed between female patients and their controls. Conclusion: The results suggest that the AR gene CAG repeat polymorphism may be one of the candidate genetic markers for male acne susceptibility in the Han population. Copyright (C) 2009 S. Karger AG, Basel