title: GAD Antibody-Associated Late-Onset Cerebellar Ataxia in Two Female Siblings.
abstract: BACKGROUND
  Anti-glutamic acid decarboxylase antibody (GAD-ab)-associated cerebellar ataxia is a rare neurological disorder characterized by cerebellar symptoms concomitant with high GAD-ab levels in serum and cerebrospinal fluid (CSF).
  
  
  METHODS
  We report on 2 female siblings (aged 74 and 76 years) presenting with gradual progression of rotational vertigo, gait ataxia and vertical diplopia, continuously progressing for 6 months and 6 years, respectively. Autoimmune laboratory examinations showed remarkably increased serum and CSF GAD-ab levels. Their medical histories revealed late-onset type 1 diabetes mellitus (T1DM) and other concomitant autoimmune disorders (Grave's disease, Hashimoto's thyroiditis). Cerebral MRI and laboratory examinations were unremarkable. The diagnosis of GAD-ab-associated cerebellar ataxia with particular brainstem involvement was established in both women. After the exclusion of an underlying malignancy, immunosuppressive therapy has been initiated in both patients, which resulted in stabilization in one and in clinical improvement in the other patient.
  
  
  CONCLUSIONS
  The unique association of autoantibody-mediated cerebellar ataxia and late-onset T1DM in 2 siblings with similar clinical and paraclinical phenotypes strengthens the concept that hereditary factors might play a relevant role also in autoimmune diseases so far considered to be sporadic. Moreover, the occurrence of continuous vertical diplopia broadens the clinical spectrum of GAD-ab-associated neurological syndromes.
authors.affiliation: Department of Neurology, Berlin, Germany ; Department of NeuroCure Clinical Research Center, Berlin, Germany.
authors.forename: Joseph
authors.initials: J
authors.lastname: Kuchling
authors.affiliation: Department of Psychiatry and Psychotherapy, Berlin, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Shababi-Klein
authors.affiliation: Department of Neurology, Berlin, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Nümann
authors.affiliation: Department of Neurology, Berlin, Germany.
authors.forename: Lea M
authors.initials: LM
authors.lastname: Gerischer
authors.affiliation: Department of Neurology, Berlin, Germany ; Department of Clinical and Experimental Multiple Sclerosis Research Center, Berlin, Germany ; Center for Autoimmune Encephalitis and Paraneoplastic Neurological Syndromes, Charité - Universitätsmedizin Berlin, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Harms
authors.affiliation: Department of Neurology, Berlin, Germany ; Center for Autoimmune Encephalitis and Paraneoplastic Neurological Syndromes, Charité - Universitätsmedizin Berlin, Germany ; German Center for Neurodegenerative Diseases (DZNE) Berlin, Berlin, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Prüss
keywords: Anti-GAD antibody; Anti-GAD65; Autoantibodies; Autoimmunity; Cerebellar ataxia; GAD