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IgG directed against the α-isoform of glial fibrillary acidic protein (GFAP-IgG) predicts a distinct corticosteroid-responsive meningoencephalomyelitis termed autoimmune GFAP astrocytopathy, when detected on cerebrospinal fluid (CSF).1 Optic disc oedema and tremor are common accompaniments. The MRI hallmark is a striking linear perivascular enhancement radially oriented around the ventricles (radial enhancement), while the myelitis component is generally associated with a longitudinally extensive T2 lesion on spinal cord MRI, similar to that typically encountered in aquaporin-4-IgG (AQP4-IgG) related myelitis.1–3 We compared the clinical, laboratory and MRI features of GFAP-IgG and AQP4-IgG related myelitis.
Materials and methods
We retrospectively identified GFAP-IgG seropositive patients seen at the Mayo Clinic ( 1 January 2000 to 31 December 2017). Inclusion criteria were as follows: (1) serum/CSF demonstrating GFAP pattern by indirect immunofluorescence with GFAPα specificity confirmed by cell-based assay, as previously described;1 (2) first myelitis episode; (3) serum sample negative for myelin oligodendrocyte glycoprotein-IgG (MOG-IgG) and AQP4-IgG using previously described methodology4 5; (4) adequate clinical data available. Nine patients with GFAP-IgG myelitis were included in a prior report.1 Two patients with dual positivity in serum for AQP4-IgG and GFAP-IgG were excluded. Medical records were reviewed and compared with 41 patients from a previously identified cohort of AQP4-IgG seropositive patients at the first episode of clinical myelitis who tested negative for GFAP-IgG (41 tested) and MOG-IgG (13 tested).5 Improvement was defined as subjective improvement reported by the patient with objective improvement confirmed by the physician.
All available MRI sequences obtained within 4 months of myelitis onset were reviewed by one neurology investigator (ES/EPF) and one neuroradiologist (TJK/KNK/PPM) as described previously.5 Consensus was achieved in situations of disagreement.
Wilcoxon rank-sum test or χ2/Fisher’s exact test was used as appropriate for comparison (JMP 8.0 software).
Fifty-four patients with myelitis were included: GFAP-IgG positive, …
Contributors ES: analysis and interpretation of data, drafting of the manuscript and figures. PPM, AM, SJP, SRH, BGW, AJA, KNK, TJK, EAJ, NLZ, AZ, DMW, JJ: acquisition of data, analysis and interpretation of data, critical revision of the manuscript for intellectual content. EPF: study concept and design, acquisition of data, analysis and interpretation of data, study supervision.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interest AM and SRH are named inventors on a patent application filed by Mayo Foundation relating to GFAP antibody. AM consulted for Grifols, Medimmune and Euroimmun and received research support from MedImmune and Euroimmun. SJP has a financial interest in patents (12/678,350 filed 2010 and 12/573,942 filed 2008) that relate to functional AQP4/neuromyelitis optica-IgG assays and neuromyelitis optica-IgG as a cancer marker. SJP has provided consultation to Alexion Pharmaceuticals, Medimmune and Chugai Pharma USA but has received no personal fees or personal compensation for these consulting activities. All compensation for consulting activities is paid directly to Mayo Clinic. SJP has received a research grant from Alexion Pharmaceuticals for an investigator-initiated study and support from the NIH(RO1 NS065829-01) and the Guthy Jackson Charitable Foundation for neuromyelitisoptica research. BGW receives royalties from RSR Ltd, Oxford University, Hospices Civil de Lyon and MVZ Labor PD Dr. Volkmann und Kollegen GbR for a patent of NMO-IgG as a diagnostic test for NMO and related disorders. He serves as a member of an adjudication committee for clinical trials in NMO being conducted by MedImmune and Alexion pharmaceutical companies. He is aconsultant for Caladrius Biosciences regarding a clinical trial for NMO.
Patient consent Not required.
Ethical approval Mayo Clinic Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.