Glutathione S-transferase M1 gene polymorphism and susceptibility to endometriosis in a French population.

Endometriosis is a multifactorial disease with possible genetic predisposition and involvement of environmental factors in its pathogenesis. The genetic polymorphism of glutathione S-transferase M1 (GSTM1) gene, which codes for glutathione S-transferase 1, class mu foreign compound conjugating enzyme of phase II detoxification system, was studied by polymerase chain reaction from the blood spots in patients with different stages of endometriosis (n = 50) and in controls (n = 72) of French origin. A total of 86.0% of patients appeared to lack GSTM1 enzyme activity due to the presence of an extended deletion (GSTM1 0/0 genotype), compared with 45.8% in a control group (P < 0.0001), which was consistent with the frequency of GSTM1 deletion in French population. Moreover, the distribution of GSTM1-active genotypes was significantly different in patients and controls (P < 0.0001), as no patient with GSTM1A/B genotype, which is correlated with the highest activity of GSTM1 enzyme, has been found so far (18.1% in a control group). The unusually high frequency of homozygotes for the GSTM1 gene deletion among patients with endometriosis suggests a possible contribution of environmental toxins in the pathogenesis of this disease due to the absence or low activity of GSTM1 enzyme.