title: GM2 gangliosidosis AB variant: novel mutation from India - a case report with a review.
abstract: GM2 gangliosidosis-AB variants a rare autosomal recessive neurodegenerative disorder occurring due to deficiency of GM2 activator protein resulting from the mutation in GM2A gene. Only seven mutations in nine cases have been reported from different population except India.
  
  
  
  Present case is a one year old male born to 3rd degree consanguineous Indian parents from Maharashtra. He was presented with global developmental delay, hypotonia and sensitive to hyperacusis. Horizontal nystagmus and cherry red spot was detected during ophthalmic examination. MRI of brain revealed putaminal hyperintensity and thalamic hypointensity with some unmyelinated white matter in T2/T1 weighted images. Initially he was suspected having Tay-Sachs disease and finally diagnosed as GM2 gangliosidosis, AB variant due to truncated protein caused by nonsense mutation c.472 G > T (p.E158X) in GM2Agene.
  
  
  
  Children with phenotypic presentation as GM2 gangliosidosis (Tay-Sachs or Sandhoff disease) and normal enzyme activity of β-hexosaminidase-A and -B in leucocytes need to be investigated for GM2 activator protein deficiency.
authors.affiliation: Department of Biochemical and Molecular Genetics, FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, 380015, Gujarat, India. jshethad1@gmail.com.
authors.forename: Jayesh
authors.identifier: 0000-0001-5936-5192
authors.initials: J
authors.lastname: Sheth
authors.affiliation: Sahyadari Medical Genetics and Tissue engineering facility (SMGTEF), Pune, 411005, India.
authors.forename: Chaitanya
authors.initials: C
authors.lastname: Datar
authors.affiliation: Department of Biochemical and Molecular Genetics, FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, 380015, Gujarat, India.
authors.forename: Mehul
authors.initials: M
authors.lastname: Mistri
authors.affiliation: Department of Biochemical and Molecular Genetics, FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, 380015, Gujarat, India.
authors.forename: Riddhi
authors.initials: R
authors.lastname: Bhavsar
authors.affiliation: Department of Biochemical and Molecular Genetics, FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, 380015, Gujarat, India.
authors.forename: Frenny
authors.initials: F
authors.lastname: Sheth
authors.affiliation: Department of Biochemical and Molecular Genetics, FRIGE's Institute of Human Genetics, FRIGE House, Jodhpur Gam Road, Satellite, Ahmedabad, 380015, Gujarat, India.
authors.forename: Krati
authors.initials: K
authors.lastname: Shah
mesh_terms: D018389:Codon, Nonsense; D049289:G(M2) Activator Protein / Q000235:genetics*; D005819:Genetic Markers; D005820:Genetic Testing; D006801:Humans; D007223:Infant; D008297:Male; D049290:Tay-Sachs Disease, AB Variant / Q000175:diagnosis / Q000235:genetics*
chemical_list: D018389:Codon, Nonsense; D049289:G(M2) Activator Protein; D005819:Genetic Markers
keywords: AB variant; GM2 activator protein; GM2 gangliosidosis; GM2A gene