GBA1 and multiple sclerosis: However, emerging data show that heterozygous carriers of glucocerebrosidase GBA [33], sphingomyelinase SMPD1 [36], galactocerebrosidase (GALC) [37], and α-galactosidase (GLA) [38] variants are as much at risk for neurodegenerative diseases such as synucleopathies and multiple sclerosis as those with recessive homozygotes.