FUCA2 and fucosidosis: In addition, increased α-l-fucosidase activity in serum is a marker of the development of colorectal and hepatocellular carcinomas.[24] Loss-of-function mutations in FUCA1 have been associated with fucosidosis, a potentially fatal disease leading to a lethal accumulation of fucosylated glycosphingolipids,[25] but it is not clear if loss of FUCA2 function yields a similar phenotype.