Early onset developmental and epileptic encephalopathy and Rett-like phenotype in a 15-year-old girl affected by Cornelia de Lange syndrome type 2 due to a SMC1A gene mutation.

Developmental and epileptic encephalopathies (DEE) are conditions in which a mutated gene may cause abnormal functioning of the central nervous system, resulting in both encephalopathy and epileptogenesis. We present a case of a girl with a DEE characterized by a Rett-like phenotype in association with febrile and afebrile clusters of focal seizures. The girl presented typical development until the age of 18 months, followed by regression. The first febrile bilateral tonic-clonic seizure was observed at 30 months of age, and the following month seizures recurred in clusters of several episodes per day every 10 days. These seizures were characterized by behavioural arrest, emotional symptoms, head turning, and followed by bilateral tonic-clonic seizures. The administration of valproic acid and levetiracetam led to prolonged seizure control. However, from the age of 7 years, she had monthly recurrent clusters of focal seizures and non-convulsive status epilepticus which occurred at different ages. Brain and spinal cord MRI showed mild non-progressive hemispheric cerebellar atrophy. A next generation sequencing panel for epilepsy identified the de novo splicing mutation c.2973+1G>A of the SMC1A gene.