Adult-Onset Alexander Disease Presenting as Atypical Parkinsonism and Autonomic Dysfunction: A Case Series.

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Introduction: Adult-onset Alexander disease (AOAD) is a rare astrocytopathy linked to the glial fibrillary acidic protein (GFAP) gene, which is known for its clinical heterogeneity and common misdiagnosis. In adults, it may present with bulbar dysfunction, pyramidal signs, ataxia, dysautonomia, cognitive decline, or parkinsonism, which often mimics atypical parkinsonian syndromes like multiple system atrophy (MSA). The purpose of this case series was to define practical clinical, radiological, and genetic cues for suspecting AOAD in adults with atypical parkinsonism, autonomic dysfunction, or paroxysmal focal symptoms, particularly when genetic findings are inconclusive. Case Presentation: Four patients, aged 40 to 59 years, had progressive and varied neurological symptoms, like gait disturbance, lower limb weakness, dysarthria, dysphagia, autonomic dysfunction, parkinsonism, cognitive decline, and paroxysmal focal deficits. Initial diagnoses were parkinsonian syndrome, stroke, transient ischemic attack (TIA), and MSA. Diagnostic Assessment and Intervention: Brain magnetic resonance imaging (MRI) in all patients showed characteristic lower brainstem abnormalities, particularly atrophy of the medulla oblongata and upper cervical spinal cord, consistent with the "tadpole sign." GFAP sequencing identified one likely pathogenic variant (p.Arg70Trp) and three variants of uncertain significance: p.Glu122_Arg124del, p.Met415Ile, and p.Glu195Val. Management was mainly symptomatic; one patient showed significant motor improvement after repetitive transcranial magnetic stimulation (rTMS). Conclusions: AOAD should be considered in adults with parkinsonism-plus syndromes or unexplained combinations of bulbar symptoms, pyramidal signs, autonomic dysfunction, and cognitive decline. Recognizing the tadpole sign on MRI may improve diagnostic accuracy, particularly when genetic results are inconclusive.

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