Relative Frequency and Distinctive Features of Anti-Ma2 Nonparaneoplastic Neurologic Disorders

BACKGROUND AND OBJECTIVES: Although anti-Ma2 antibodies (Ma2-Abs) typically associate with paraneoplastic encephalitis, a subset of patients with Ma2-Abs does not have any detectable tumor. The clinical specificities of these idiopathic cases are unknown. The aim of this study was to describe clinical phenotypes and outcomes of patients with idiopathic Ma2-Abs (I-Ma2) compared with patients with paraneoplastic Ma2-Abs (PNS-Ma2). METHODS: A retrospective review of the French Reference Center of Paraneoplastic Neurologic Syndromes and Autoimmune Encephalitis database was conducted to identify cases of Ma2-Abs-mediated syndromes diagnosed between January 2002 and December 2022. A systematic review of the existing literature was also performed to assess for reported I-Ma2 cases. RESULTS: = 0.00325, respectively). DISCUSSION: Patients with I-Ma2 are more common than anticipated and have insidious disease onset and a tendency for monofocal nervous system involvement. Recognition of patients with I-Ma2 is delayed and must be improved.