Distinct features of ANCA-associated hypertrophic pachymeningitis compared to other etiologies: findings from a study of 74 patients

Abstract Objectives We aimed to characterize the clinical and radiological features, and outcomes, of a large cohort of hypertrophic pachymeningitis (HP) patients from a single centre. Methods We conducted a retrospective study at a tertiary referral centre, encompassing patients diagnosed with HP between 2003 and 2022. The diagnosis of HP relied on the identification of thickening of the dura mater via MRI of the brain or spine. Results We included 74 patients, with a mean age of 43.6 ± 14.2 years, of whom 37 (50%) were male. Among the 74, 32 (43.2%) had an immune-mediated origin, including 21 with granulomatosis with polyangiitis (GPA) (predominantly PR3-ANCA positive), four with SLE, three with IgG4-related disease, three with idiopathic HP, and one with RA. Non-immune-mediated HP accounted for 45 cases (56.8%). Within this category, 21 (28.4%) were infectious cases, with 14 having Mycobacterium tuberculosis infection (TB-HP), and 21 (28.4%) having malignancy-associated HP. The clinical and MRI characteristics exhibited variations among the four etiological groups. Hypoglycorrhachia was primarily observed in infectious HP and malignancy-associated HP. Immune-mediated HP was associated with a peripheral pattern of contrast enhancement and the Eiffel-by-night sign. MRI features strongly indicative of TB-HP included leptomeningeal involvement, brain parenchymal lesions, and arterial stroke. MPO-ANCA GPA was associated with a higher prevalence of spinal HP. Conclusios Within our cohort, GPA and Mycobacterium tuberculosis emerged as the predominant causes of HP. We identified significant disparities in clinical and radiological features among the various etiologies, which could have implications for diagnosis.