Novel SLC6A9 variants in an adult presenting with GlyT1 encephalopathy.
Mark Mencias, Meneka Kanagaratnam, Emma Matthews
✦ AI-curated · Sources linked
Case in brief
A 27-year-old man with GlyT1 encephalopathy was found to carry two novel compound-heterozygous SLC6A9 variants. His features included neonatal hypotonia followed by hypertonicity, respiratory failure, exaggerated startle and arthrogryposis. His clinical course stabilised after early childhood, and perampanel was reported to significantly benefit the exaggerated startle. He also had significant visual loss, for which no cause was established; a possible link to GlyT1 function in retinal amacrine cells was proposed but remains speculative.
What made this case unusual
Survival to age 27 extends the described age range for this disorder and offers additional phenotypic and prognostic information in a condition associated with high early mortality.
Diagnostic / clinical pearl
Consider biallelic SLC6A9-related GlyT1 encephalopathy in patients with the characteristic combination of neonatal hypotonia, later hypertonicity, respiratory failure, exaggerated startle and arthrogryposis.