LAUSR

Objective Hypertrophic pachymeningitis (HP) related to anti-neutrophil cytoplasmic antibody (ANCA) is the most frequently seen immune-mediated HP. We investigated cerebrospinal fluid (CSF) biomarkers related to the pathogenesis of ANCA-related HP (ANCA-HP). Methods The levels of B cell activation factor of the tumor necrosis factor family (BAFF), a proliferation-inducing ligand (APRIL), and transforming growth factor beta 1 (TGF-β1) in the CSF were compared between patients with ANCA-HP ( n  = 12), other types of immune-mediated HP (other HP; n  = 12), multiple sclerosis (MS; n  = 14), and non-inflammatory neurological disorders (NIND; n  = 10). In addition, we evaluated whether ANCA would be detected in CSF. Results CSF levels of BAFF, APRIL, and TGF-β1 were significantly increased in ANCA-HP and other HP. In particular, BAFF and APRIL levels were significantly correlated with the IgG index in ANCA-HP. In other HP, BAFF and APRIL levels were significantly correlated with cell counts and protein levels in CSF. Of 12 patients with ANCA-HP, the CSF of 7 patients (58%) tested positive for myeloperoxidase (MPO)- or proteinase 3 (PR3)-ANCA, while none of the CSF samples from other HP, MS, or NIND patients tested positive. Conclusion The levels of BAFF, APRIL, and TGF-β1 may serve as useful CSF biomarkers for assessing the disease activity of immune-mediated HP. Moreover, BAFF and APRIL in the CSF may be implicated in the pathogenesis of ANCA-HP via promoting autoreactive B cells, while detecting MPO- or PR3-ANCA in the CSF may be found in some patients with ANCA-HP. Key Points • CSF BAFF, APRIL, and TGF-β1 levels increase significantly in immune-mediated HP. • CSF BAFF and APRIL levels are significantly correlated with IgG index in ANCA-HP. • Detection of MPO- or PR3-ANCA in the CSF is found in some patients with ANCA-HP. • BAFF, APRIL, and ANCA in the CSF may be implicated in the pathogenesis of ANCA-HP.