Abstract Fabry disease (FD) is an X-linked inborn error of glycosphingolipid metabolism characterized by progressive lysosomal deposition of partially metabolized substrates within various tissues. This condition results in significant morbidity and mortality for both men and women. However, the severity and progression of the disease differ by sex due to potential factors that modulate the phenotype in women, such as X chromosome inactivation. In this study, we conducted methylation assays on peripheral blood samples from seven women diagnosed with FD and examined the correlation between these assays and the clinical severity of the disease. The results showed no correlation, underscoring the importance of selecting appropriate tissues for analysis.