Estimated prevalence and distribution of causes of immune-mediated hypertrophic pachymeningitis in São Paulo, Brazil.

Abstract

BACKGROUND: The prevalence of hypertrophic pachymeningitis (HP) remains poorly defined worldwide. In Japan, the estimated prevalence is 0.949 cases per 100,000 inhabitants, with most cases related to ANCA-associated vasculitis or IgG4-related disease. In contrast, epidemiological data from other regions, including Latin America, are scarce. METHODS: This study was conducted at a tertiary referral center in the city of São Paulo, Brazil. The prevalence of HP was estimated by comparison with the known prevalence of multiple sclerosis (MS), based on the number of patients with each condition followed at our institution. The etiological distribution of HP was also analyzed. In addition, HP prevalence was compared with that of tuberculous meningoencephalitis, a compulsory notifiable disease and a well-established cause of chronic meningitis in Brazil, using data from the national surveillance system (SINAN). RESULTS: We identified 55 patients with HP: 36 (65%) idiopathic, 10 (18%) IgG4-related disease, 4 (7%) ANCA-associated pachymeningitis, 4 (7%) probable or definite neurosarcoidosis, and 1 (2%) secondary to rheumatoid arthritis. Among 968 registered MS patients and assuming an MS prevalence of 15 per 100,000 inhabitants in São Paulo, the estimated HP prevalence was 0.85 per 100,000 inhabitants. This estimate was comparable to the prevalence of tuberculous meningoencephalitis in the same region. CONCLUSION: The estimated prevalence of HP in São Paulo (0.85 per 100,000) is consistent with reports from other regions and is comparable to that of tuberculous meningeal disease, although with a distinct etiological profile. IgG4-related disease was the most frequent systemic association, differing from previous reports. ANCA-associated HP appears to be less frequent than in other geographic regions, possibly reflecting differences in disease phenotype. Key Points • The estimated prevalence of HP in São Paulo was 0.85 per 100,000 inhabitants. • IgG4-related disease was the most common systemic disease identified among patients with HP. • ANCA-associated HP was less common than reported in Asian and European cohorts. • The prevalence of HP was comparable to that of tuberculous meningoencephalitis in São Paulo.