Early myoclonic encephalopathy in 9q33-q34 deletion encompassing STXBP1 and SPTAN1

Deletions in the 9q33-q34 region have been reported in patients with early onset epileptic encephalopathy, but a consistent phenotype has yet to emerge. We report on the diagnosis of a de novo 9q33-q34.12 microdeletion of 4 Mb in a 15-month-old girl presenting with severe psychomotor delay, facial dysmorphisms, thin corpus callosum and early myoclonic encephalopathy. This deletion encompasses 101 RefSeq genes, including the four autosomal dominant genes STXBP1, SPTAN1, ENG and TOR1A. We discuss genetic, clinical and epileptic features comparing our patient with those previously reported in the literature.