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E.I. Traboulsi, F. Farukhi, C. Dakouri, H. Wang; Etiology of Vision Loss in GM3 Synthase Deficiency . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4615.
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GM3 synthase deficiency is an extremely rare autosomal recessive infantile–onset symptomatic epilepsy syndrome associated with developmental stagnation and blindness. The disorder was mapped to 2p12– p11.2 in a large Old Order Amish pedigree, and the defect was subsequently found to be the result of homozygosity for a nonsense mutation in SIAT9, and leads to the premature termination of the GM3 synthase enzyme (also called lactosylceramide alpha–2,3 sialyltransferase). Although patients with GM3 synthase deficiency were described as blind from optic nerve atrophy in the original publication (Nat Genet. 2004;36:1225–9) no details of the ocular examinations were given.
We examined four children from two related Amish sibships. Molecular genetic analysis confirmed inheritance of the founder mutation. Electroretinography and fundus photography were obtained in two patients.
Despite an initial suspicion of retinal degeneration, retinal function was preserved in both patients and ERG amplitudes were within normal limits. Ophthalmoscopy showed bilateral optic atrophy in all patients.
Vision loss in GM3 synthase deficiency results from central nervous system and optic nerve involvement. Retinal function is otherwise normal.
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