MOG antibody-associated disease (MOGAD) is a demyelinating syndrome with distinct clinical and prognostic features. There remains a pressing need for biomarkers of relapse risk. CSF biomarkers such as oligoclonal bands might not be abnormal in MOGAD, and they do not reliably predict relapse risk. Intrathecal production of the chemokine CXCL13, estimated by the CXCL13 index, has proven to be a helpful biomarker in clinically isolated syndrome and multiple sclerosis. To date, the CXCL13 index has not been investigated in MOGAD.

A 34 year-old woman presented with descending progressive numbness over two weeks. A longitudinally extensive enhancing cervicothoracic lesion was discovered. Cerebrospinal fluid (CSF) showed 48 nucleated cells (95% lymphocytes) and normal/negative CSF protein, anti-MOG and anti-NMO antibodies, oligoclonal bands, and IgG index.  Though diagnosed with transverse myelitis, she fully recovered after corticosteroids. Without evidence for a chronic autoimmune condition, disease modifying therapy was not started. She consented to enrollment in an IRB-approved CSF Biobank study. CXCL13 index was elevated to 123. CSF CXCL13 concentration was markedly elevated at 52.1 pg/ml. For comparison, the mean CXCL13 index of 67 CSF/sera from controls with non-inflammatory neurological diseases (e.g. migraine) was 6.9, with a mean+2 SD of 16.4 (DiSano et al., 2020).  Two years later, the patient presented again with right optic neuritis and recurrent myelitis. She was again treated with steroids and improved. MOG IgG antibody status seroconverted to positive (1:1000).  Rituximab was started for prevention. She did well for 18 months before recurrence with a mild cervical myelitic attack, which completely resolved. She was transitioned to maintenance IVIg.

In the present case, CXCL13 index was elevated prior to a relapse. This case supports the hypothesis that CXCL13 Index may be a helpful predictive biomarker for relapses in MOGAD, though larger studies are warranted.