ABSTRACT
Abstract Fabry disease, caused by deficient alpha-galactosidase A lysosomal enzyme activity, remains challenging to health-care professionals. Laboratory diagnosis in males is carried out by determination of alpha-galactosidase A activity; for females, enzymatic activity determination fails to detect the disease in about two-thirds of the patients, and only the identification of a pathogenic mutation in the GLA gene allows for a definite diagnosis. The hurdle to be overcome in this field is to determine whether a mutation that has never been described determines a ''classic'' or ''nonclassic'' phenotype, because this will have an impact on the decision-making for treatment initiation. Besides the enzymatic determination and GLA gene mutation determination, researchers are still searching for a good biomarker, and it seems that plasma lyso-Gb3 is a useful tool that correlates to the degree of substrate storage in organs. The ideal time for treatment initiation for children and nonclassic phenotype remains unclear.