Leukodystrophy in a Chinese boy: a novel FUCA1 mutation causing Fucosidosis (Case Report)

Abstract

Fucosidosis is a autosomal recessive neurodegenerative condition. It is a lysosomal storage disorder caused by deficient α-1-fucosidase activity leading to accumulation of fucose-containing glycolipids and glycoproteins in various tissues. We report a 5-year-old Chinese boy with parental consanguinity. He presented with global developmental delay and magnetic resonance imaging evidence of leukodystrophy. He was later found to have decreased α-fucosidase activity in peripheral leukocytes (2.4nmol/mg protein/hr; control 24–162) and skin fibroblast cultures (0.24nmol/mg protein/hr; control 96–360). His development became static at 2.5 years and deteriorated gradually after that. The FUCA-1 gene was analyzed by generating complementary DNA from total RNA isolated from his (cultured) skin fibroblasts. Two known homozygous polymorphism, S264C (809C3G) and Q281R (860A3G), were detected. A homozygous single-base substitution (396T3A) was found in exon 2, causing a stop codon mutation (Y126X). This sequence is not found within the FUCA pseudogene and is a novel mutation. Previously, 22 mutations of the FUCA1 gene and 3 additional mutations have been reported. Including our report, the 26 FUCA1 mutations are predominantly nonsense mutations (19/26), resulting from either point mutations or deletions. The relative scarcity of missense mutations (4/26) may imply the presence of alternate or compensatory enzymatic pathways capable of modifying the clinical severity. Identification of molecular defect in this child could help future prenatal diagnosis for this family.