LAUSR

OBJECTIVE Mutations in the ATP1A3 gene cause the classical disorders of rapid-onset dystonia-parkinsonism (RDP), alternating hemiplegia of childhood (AHC) and cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS). However, intermediate phenotypes have also been described, making the range of clinical manifestations associated with mutations in the ATP1A3 gene wider. A rare case of an ATP1A3 gene mutation is presented. CASE REPORT Genetic testing was performed in a neonate who presented with neurological abnormalities on day 2 of life, severe electrolytic disturbances a few days later and developmental delay and epilepsy a few months later. A pathogenic heterozygous missense mutation in the ATP1A3 gene (c.2482G>A, E828K(p.Glu828Lys) was detected on clinical exome sequencing. CONCLUSIONS The present case report extends the already described phenotypic variation observed in individuals with ATP1A3 gene mutations. It also illustrates the importance of genetic testing in the case of complex and not straightforward clinical scenarios, particularly when present from a very young age, before clinical criteria for known diagnoses are met.