Clinical Presentation, Investigation Findings, and Outcomes of IgG4-Related Pachymeningitis: A Systematic Review.

Importance: Immunoglobulin G4 (IgG4)-related disease is an increasingly recognized fibroinflammatory condition that can involve multiple organs, including the pachymeninges. The understanding of IgG4-related pachymeningitis (IgG4-RP) remains limited because of its rarity and the predominance of knowledge derived from case reports and case series.

Objective: To systematically review and synthesize the clinical presentation, investigation findings, and prognosis of IgG4-RP to better understand its diagnosis and management.

Evidence review: A comprehensive systematic review was conducted following guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-analyses. PubMed/MEDLINE, Embase, and Scopus were searched from their inception until May 30, 2023, using terms related to IgG4-related disease and pachymeningitis without language or publication restrictions. Case reports and series that met the 2020 Revised Comprehensive Diagnostic Criteria or the 2019 American College of Rheumatology/European League Against Rheumatism classification criteria were included. Data on clinical presentations, investigation findings, and treatment outcomes were extracted and summarized.

Findings: A total of 148 case reports contributed data from 208 patients. Their median (IQR) age was 52 (39-62) years; 132 patients were male (63.5%) and 76 female (36.5%). Headache and cranial nerve dysfunctions were the most common neurological manifestations. Systemic involvement was identified in nearly half of the patients. Diagnostic imaging often showed preferential involvement of cavernous sinus and middle fossa. Laboratory results highlighted elevated serum IgG4 levels in 97 of 147 patients (65%) of patients and cerebrospinal fluid pleocytosis in 43 of 82 patients (52%). Storiform fibrosis or obliterating phlebitis were uncommon pathological findings. Mortality was below 1% (1/134; 0.7%), but only a third of patients presented complete clinical improvement, and the recurrence rate was 60 patients (40%) in a median (IQR) follow-up time of 9 (1-20) months. Glucocorticoids were the most commonly prescribed treatment, in 143 of 169 patients (85%); rituximab was prescribed as maintenance therapy in 53 of 169 patients (31%).

Conclusions and relevance: IgG4-RP commonly presents with headaches and cranial nerve dysfunction, posing diagnostic challenges due to the significant absence of systemic manifestations, low IgG4 serum levels, and atypical pathological findings. Current treatment outcomes are limited by incomplete recovery and frequent relapses underscoring the necessity for new treatment strategies.