Background

The glutathione S-transferase mu 1 (GSTM1) gene is located in the 1p13.3 band and codes for the cytosolic enzyme GST-μ that plays a role in carcinogen detoxifica-tion. Many structural variations have been described that overlap this gene in the Database of Genomic Variation [1] (Figure 1). A common copy number variant (CNV) has been well characterized and reported on the basis of the frequency of homozygous deletions of the entire coding region (known as the GSTM1-null genotype), which varies between 29 % and 51 % across ethnic groups [2-4]. Due to the established role of GSTM1 in detoxification and the high frequency of homozygous deletions in the population, GSTM1 has been extensively investigated in association with many chronic diseases, in particular, with asthma [5] and different types of cancers [4,6], in-cluding bladder cancer [7]. In a large case–control study, we reported that 63 % of bladder cancer cases and 47% of controls harbored the GSTM1-null genotype, leading to an OR = 1.7 (95%CI 1.4 – 2.0) [8]. This is a well