Atypical MRI features in familial adult onset Alexander disease: case report
In this report, we describe the case of a new Japanese family (32 to 64 years old; 2 females and 1 male) affected by adult-onset Alexander disease. Clinically, one member (age at onset, 56 years old) developed cerebellar ataxia, another (age at onset, 55 years old) showed cerebellar ataxia and pseudobulbar signs, and one member (32 years old) was asymptomatic. Marked atrophy of the medulla oblongata and spinal cord was detected in the two symptomatic patients by magnetic resonance imaging (MRI). However, in the asymptomatic patient, cervicomedullary atrophy was mild. Hyperintensity signals in the medulla oblongata were detected in the two symptomatic patients, but not in the asymptomatic patient. In addition, there are symmetrical hyperintensity signals in the posterior part of the globus pallidus on T2-weighted images in the two symptomatic patients, which are rarely observed in adult-onset Alexander disease. Molecular genetic analysis revealed a novel missense mutation (p. D78N) in the glial fibrillary acidic protein (GFAP) gene in this family. The typical atrophy of the medulla oblongata and upper cervical cord detected by MRI is the diagnostic feature of adult-onset Alexander disease. Genetic analysis of the GFAP gene is recommended for all patients with late-onset progressive ataxia and suspected of having adult-onset Alexander disease on the basis of MRI findings. Additionally, these characteristic MRI patterns might even lead to the identification of asymptomatic cases, as in one of our cases.