MR imaging findings in 2 cases of late infantile GM1 gangliosidosis.

Late infantile GM1 gangliosidosis is a rare lysosomal disorder characterized by mental deterioration and progressive spastic, cerebellar, and extrapyramidal signs, without facial dysmorphisms and organomegaly. Neuroimaging findings have been reported in only a few cases. Here we report on predominant globus pallidus MR signal-intensity abnormalities in 2 patients with the late infantile form of GM1 gangliosidosis. GM1 gangliosidosis is a rare metabolic disorder due to deficiency of the lysosomal enzyme β-galactosidase, resulting in accumulation of GM1 gangliosides and other glycoconjugates in the brain and visceral organs. There are 3 clinical forms correlating with the degree of residual activity of the mutant enzyme. The infantile form (type 1) is a severe degenerative encephalopathy presenting between birth and 6 months with coarse facial features, skeletal dysostosis, and hepatosplenomegaly, leading to death within the first 2 years of life. Patients with the late infantile or juvenile form (type 2) present after 1 year of age with motor delay in the absence of dysmorphisms and organomegaly; later, mental deterioration and spastic, cerebellar, and extrapyramidal signs dominate the neurologic picture, probably as a consequence of predominant basal ganglia storage of gangliosides.1 The adult form (type 3) has a slowly progressive course and predominant extrapyramidal features without visceral or skeletal changes.2 Reports on the neuroimaging features of the very rare late infantile GM1 gangliosidosis are scant and have mainly included brain atrophy and white matter and basal ganglia abnormalities.3,4 We report 2 young patients in whom MR imaging predominantly showed evidence of globus pallidum paramagnetic ion accumulation.