Table 1. Clinical and genetic features of GM2A-associated disease.

Source	Mutation	Ethnicity	Age of Onset	Symptoms	Examination	Other
de Baecque, et al.12	p.C107R homozygous	African American	9 months	Decline in mobility; hyperacusis; regression	Hypotonia; increased DTRs; cherry red spots	Normal HexA and HexB activities; brain biopsy showed Zebra bodies and membranous cytoplasmic bodies; pleomorphic intracytoplasmic astrocytic inclusions; reported by Schroder et al.3 and Xie et al.4
Schroder et al.13	p.R169P homozygous	Indian	5 months	Nystagmus, motor delay	Hyperacusis; juvenile spasms; cherry red spot	Normal HexA and HexB activities; rectal biopsy showed storage material; died at age 5
Schepers et al.6	p.H137fsX33 homozygous	Spanish	7 months	Developmental delay	Hypotonia, limb hypertonia; hyperacusis; cherry red spots	Normal HexA and HexB activities; MRI showed ↑ cerebral and cerebellar white matter signal
Schepers et al.6	p.88Ldel homozygous	Saudi	8 months	Weakness; head lag; infantile spasms; tonic–clonic seizures	Hypotonia; ↓ visual attention; hyperacusis; cherry red spots	Normal HexA and HexB activities; diffuse brain atrophy on MRI; rapid progression after 24 months
Chen et al.7	p.E54X homozygous	Laotian Hmong	5 months	Developmental delay; weakness; extreme hyperacusis; generalized tonic–clonic and myoclonic seizures	Severe hypotonia; dysarthria, dysphagia; ↓ volitional movement; ↓ response to environment; roving eye movements; cherry red spots	Normal HexA enzyme activity; ↑ CSF gangliosides; abnormal basal ganglia and white matter signal
Present report (3 patients)	p.P55L homozygous	Saudi	7 or 8 years	Anxiety, intellectual regression, chorea	Spastic quadriparesis, limb dystonia, pyramidal tract signs, chorea	Diffuse cortical atrophy

Hex A, Hexosaminidase A; Hex B, Hexosaminidase B; MRI, Magnetic Resonance Imaging.