Late onset GM2 gangliosidosis mimicking spinal muscular atrophy

• Late onset GM2 with spinal SMA phenotype followed by cerebellar symptoms and dystonia.
• Compound heterozygous mutation in exon 10 of the HEXA gene.
• MRI of the brain showed cerebellar atrophy consistent with MRS abnormalities.
• FDG PET/CT showed hypometabolism in cerebellum and in temporal and occipital cortex.

A case of late onset GM2 gangliosidodis with spinal muscular atrophy phenotype followed by cerebellar and extrapyramidal symptoms is presented. Genetic analysis revealed compound heterozygous mutation in exon 10 of the HEXA gene. Patient has normal intelligence and emotional reactivity. Neuroimaging tests of the brain showed only cerebellar atrophy consistent with MR spectroscopy (MRS) abnormalities. (18)F-fluorodeoxyglucose positron emission tomography (18)F-FDG PET/CT of the brain revealed glucose hypometabolism in cerebellum and in temporal and occipital lobes bilaterally.