Abstract

We describe the seizure phenotype of a 26 year old lady who presented with a probable photic-induced convulsion on a background of mild intellectual disability, facial dysmorphia, fused cervical vertebrae and ventricular septal defect. There was no prior history of seizures.

Routine EEG was polyrhythmic with a prominent photoparoxysmal response at 14 Hz and 40 Hz. CT head was normal. A SNP array demonstrated a rare 51 kb deletion at 12 p12.1 which disrupts the SOX5 gene.

SOX5 is a developmentally important gene encoding a transcription factor that plays a role in multiple developmental pathways including of the nervous system. Loss of function of this gene is associated with Lamb-Shaffer syndrome, first characterised in 2012 with global developmental delay, intellectual disability, mild dysmorphic facies, language impairment and variable skeletal abnormalities.

3 of the original cohort of 16 patients described experienced seizures and the nature of their epilepsy was not further defined. Only a further 7 cases have been reported to date, none of whom experienced seizures. Our case helps to broaden the phenotype of Lamb-Shaffer syndrome, highlights the importance of looking for copy number variation and poses questions regarding the neurobiology of photo-sensitivity.