c.1289G>A (p.Arg430His) variant in the epsilon isoform of the GFAP gene in a patient with adult onset Alexander disease

Abstract

Alexander disease (AD) is a rare form of leukodystrophy caused by pathogenic variants in the GFAP gene. In young children the condition is fatal, while adults have variable neurological symptoms and prognosis. On magnetic resonance imaging, a pattern of atrophy of the medulla oblongata and cervical spinal cord with a 'tadpole' appearance is highly suggestive of adult-onset Alexander disease (AOAD). GFAP gene sequencing is used to confirm the diagnosis. Pre-mRNA of this gene undergoes alternative splicing resulting in formation of at least 8 different protein isoforms. Most patients with AD described to date have a pathogenic variant in the coding sequence of the main and the most abundant gene isoform, the GFAPα. Recently, two half-siblings with neurological symptoms and radiological signs of AOAD were reported and were not found to have any pathogenic variants in the GFAPα gene while further genetic testing by next generation sequencing revealed a c.1289G>A (p.Arg430His) variant in the alternative exon 7A of the GFAPε isoform. Here we present a case of another patient with symptoms and brain MRI pattern suggestive of AOAD. Similarly to the previously described patients, this patient did not have any pathogenic variants in the main gene isoform and had the same c.1289G>A (p.Arg430His) variant in the GFAPε. This report contributes to evidence of pathogenicity of the c.1289G>A (p.Arg430His) variant in the GFAPε.

Keywords: Alexander disease; Cervicomedullary atrophy; GFAP; GFAPδ; GFAPε.