Hemimegalencephaly associated with drug-resistant epilepsy and a rare molecular genetic alteration in the CPA6 gene: a clinical case

Hemimegalencephaly (HME) is one of the extremely rare congenital malformations of cortical development (MCD). It belongs to the MCD group of mTOR-related pathologies and can be the result of various genetic disorders. One of the main clinical manifestations of HME is drug-resistant epilepsy requiring surgical treatment.

Case report. This article describes a clinical case of HME in a 4-year-old boy with frequent generalized tonic-clonic seizures and drug-resistant epilepsy; also, he had speech development delay. MRI revealed a HME of the right frontal lobe. Stereotaxic laser disconnection of the large cortical dysplasia in the right frontal lobe of the brain was performed. Morphological features of focal cortical dysplasia type IIb (FCD IIb) were reported. No seizures were observed in the hospital follow up after the operation for 14 days. The whole exome DNA sequencing showed the presence of a heterozygous state _000008.10^G 68419028del / 633del, pGlu212LysfsTers of the CPA6 gene.

Discussion. A feature of the case is the identified association of HME, morphologically represented by FCD IIb, with a previously unknown heterozygous state in the 6th exon of the CPA6 gene. This association allows to expand our understanding of changes in the activation of PI3K/AKT/mTOR pathway as a key link in the pathogenesis of congenital anomaly of cortical development.