Identification of a novel GLB1 mutation in a consanguineous Pakistani family affected by rare infantile GM1 gangliosidosis.

Monosialotetrahexosylganglioside (GM1) is a rare lysosomal storage disorder caused by the deficiency of beta-galactosidase (β-Gal) encoded by galactose beta 1 (GLB1). It is clinically characterized by developmental delay attributed to multifold accumulation of GM1 gangliosides in nerve cells. In this study, we present a case of infantile GM1 gangliosidosis in a consanguineous Pakistani family. The child was presented with developmental delay, hepatosplenomegaly and recurrent chest infections at 7.5 months of age. Radiological and biochemical investigations including magnetic resonance imaging (MRI), bonemarrow biopsy and urine oligosaccharide analyses suggested lysosomal storage disorder. Significantly low levels of β-Gal enzyme confirmed the diagnosis of GM1 gangliosidosis. DNA sequencing of GLB1 identified a homozygous 2-bp deletion c.881-882delAT (p.Tyr294Terfs) in exon 8. In silico analysis supported the deleterious effect of the variant. This study extends GLB1 mutation spectrum and should benefit genetic counselling and prenatal diagnosis of the affected family.