Adult Onset Alexander Disease Presenting as Psychogenic Polydipsia Induced Recurrent Hyponatremia as the Initial Symptom: A Case Report.
Abstract BackgroundAlexander disease (AxD, OMIM 203450) is a rare and generally fatal disorder of the central nervous system associated with heterozygous mutations in glial fibrillary acidic protein (GFAP) gene. Neuroradiological and clinical features of adult onset AxD is characterized by involvement of hindbrain structures. Psychiatric manifestations and extensive white matter lesions are very sparse in adult onset AxD.Case presentationWe diagnosed a female with AxD presenting with recurrent hyponatremia caused by psychogenic polydipsia as initial symptom at the onset age of 52-year-old. Neurological examination revealed slightly cognitive decline and brisk deep tendon reflex (DTR) in bilateral lower limbs. The symptoms commonly seen in adult onset AxD such as pseudobulbar signs, ataxia and spasticity were not found in the clinical course of disease. Her mother and elder brother had a history of schizophrenia. The patient has had a history of compulsive water drinking as well as personality change in recent years. Her brain magnetic resonance imaging (MRI) showed extensive involvement of white matter without atrophy of medulla oblongata and cervical spinal cord. The next generation DNA sequencing (NGS) showed a likely pathogenic nonsense mutation C1237C>T(pR413*) in GFAP-ε isoform.ConclusionsOur report enriches the understanding of familial adult onset AxD. Our case also contributes to evidence of pathogenicity of the variants in GFAP-ε as the cause of adult onset AxD.