Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis in Mexican Population: Clinical Phenotype, Autoantibody Profile and Renal Characteristics

Objective: To describe the clinical, serological characteristics, and renal histology in Mexican patients with antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV). Methods: Forty patients with diagnosis of AAV and renal biopsy, followed at a tertiary care center in Mexico City from 2002-2012 were retrospectively studied. Demographics, comorbidities, clinical, laboratory variables, disease activity, mortality, renal variables and histological classes were analyzed. Additionally, 50 patients with AAV, and a control group (other systemic vasculitis, systemic lupus erythematosus, infections, healthy subjects) were studied transversally to assess the prevalence of specific antibodies (ANCA, MPO, PR3, cathepsin G, lysozyme, lactoferrin, BPI and elastase), and their association with clinical manifestations. Results: Granulomatosis with polyangiitis (GPA) was the predominant phenotype, and median age at diagnosis was 53 years. High disease activity (BVAS/GPA=24), general symptoms (98%), renal (80%), pulmonary (63%), and ear, nose and throat (ENT) (58%) involvement were frequent at diagnosis. Renal damage was present at diagnosis (serum creatinine 3.9 mg/dl, estimated glomerular filtration rate 16 ml/min, 24 hr proteinuria 2.5 g, 15% on dialysis). The most prevalent renal histological class was sclerotic (58%), followed by mixed (32%), focal (8%), and crescentic (2%). No significant differences were found between histological classes in comorbidities, clinical, renal and laboratory variables, or survival. The main ANCA immunofluorescence pattern was C-ANCA (68%), followed by XANCA (22%), and P-ANCA (18%). PR3-ANCA (high sensitive) was the most frequent antibody, positive in 86%, while positivity for MPO-ANCA was observed in 18%. ANCA positivity was more frequent in patients with AAV than the control group (p<0.001). Antibodies directed to minor targets were infrequent in patients with AAV (2%). No significant correlations were identified between autoantibodies and clinical manifestations. Conclusion: GPA phenotype, C-ANCA and PR3-ANCA positivity, high disease activity, chronic renal damage, general symptoms, ENT and lung involvement at diagnosis distinguish our population with AAV.