Floris, Valentina

Abstract Background Differentiating neuromyelitis optica spectrum disorder (NMOSD) from its mimics is crucial to avoid misdiagnosis, especially in the absence of aquaporin‐4‐IgG. While multiple sclerosis (MS) and myelin oligodendrocyte glycoprotein‐IgG associated disease (MOGAD) represent major and well‐defined differential diagnoses, non‐demyelinating NMOSD mimics remain poorly characterized. Methods We conducted a systematic review on PubMed/MEDLINE to identify reports of patients with non‐demyelinating disorders that mimicked or were misdiagnosed as NMOSD. Three novel cases seen at the authors' institutions were also included. The characteristics of NMOSD mimics were analyzed and red flags associated with misdiagnosis identified. Results A total of 68 patients were included; 35 (52%) were female. Median age at symptoms onset was 44 (range, 1–78) years. Fifty‐six (82%) patients did not fulfil the 2015 NMOSD diagnostic criteria. The clinical syndromes misinterpreted for NMOSD were myelopathy (41%), myelopathy + optic neuropathy (41%), optic neuropathy (6%), or other (12%). Alternative etiologies included genetic/metabolic disorders, neoplasms, infections, vascular disorders, spondylosis, and other immune‐mediated disorders. Common red flags associated with misdiagnosis were lack of cerebrospinal fluid (CSF) pleocytosis (57%), lack of response to immunotherapy (55%), progressive disease course (54%), and lack of magnetic resonance imaging gadolinium enhancement (31%). Aquaporin‐4‐IgG positivity was detected in five patients by enzyme‐linked immunosorbent assay ( n = 2), cell‐based assay ( n = 2: serum, 1; CSF, 1), and non‐specified assay ( n = 1). Conclusions The spectrum of NMOSD mimics is broad. Misdiagnosis frequently results from incorrect application of diagnostic criteria, in patients with multiple identifiable red flags. False aquaporin‐4‐IgG positivity, generally from nonspecific testing assays, may rarely contribute to misdiagnosis.

Background Myelin-oligodendrocyte-glycoprotein (MOG)-IgG-positivity in patients with typical MS lesions on MRI may lead to diagnostic/therapeutic uncertainty. Objective and Methods We reviewed reports of cases with MS phenotype on MRI and MOG-IgG-positivity published in Pubmed between 01/2012–06/2021. Results Sixteen patients were included (median age [range], 37,5 [25–66] years; 60% female). Three patients initially tested negative for MOG-IgG. Disease course was: relapsing-remitting, 10; or progressive, 6. Intrathecal IgG-synthesis was common (79%). Low and high-efficacy MS-targeted agents prevented relapses in 30% and 100%, respectively. None of the patients showed resolution of MRI T2-lesions over time. Conclusions MOG-IgG-positivity is unlikely to alter the expected treatment response and outcomes in patients with otherwise typical MS phenotype on MRI.