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

OBJECTIVES:We aimed to characterize the clinical and radiological features, and outcomes, of a large cohort of hypertrophic pachymeningitis (HP) patients from a single center. METHODS:We conducted a retrospective study at a tertiary referral center, encompassing patients diagnosed with HP between 2003 and 2022. The diagnosis of HP relied on the identification of thickening of the dura mater via magnetic resonance imaging (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 them, 32 (43.2%) had an immune-mediated origin, including 21 with granulomatosis with polyangiitis (GPA) (predominantly PR3-ANCA positive), four with systemic lupus erythematosus, three with IgG4-related disease, three with idiopathic HP, and one with rheumatoid arthritis. Non-immune-mediated HP accounted for 45 cases (56.8%). Within this category, 21 (28.4%) were infectious cases, with 14 being Mycobacterium tuberculosis infection (TB-HP), and 21 (28.4%) were malignancy-associated HP. Clinical and MRI characteristics exhibited variations among the four etiological groups. Hypoglycorrhachia was primarily observed in infectious 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. CONCLUSIONS:Within our cohort, GPA and Mycobacterium tuberculosis emerged as the predominant causes of HP. We identified significant disparities in clinical and radiological features among different etiologies, which could have implications for diagnosis.