Age-Related Variations in the Clinical Presentation and Treatment Outcomes of New-Onset GPA: A Longitudinal Study

Background/Objectives: This study compares the clinical features and treatment outcomes of granulomatosis with polyangiitis (GPA) based on age at onset. Methods: A retrospective longitudinal cohort of patients with GPA diagnosed between January 1978 and December 2015 was analyzed, stratified by age at diagnosis: ≤30 years (young group), 31-59 years (middle-aged group), and ≥60 years (older group). The comparative analysis included demographic data, organ involvement, laboratory results, anti-neutrophil cytoplasmic antibody (ANCA) status, comorbidities, treatments, and outcomes. Results: The analysis included 264 patients newly diagnosed with GPA. Older patients exhibited significantly higher rates of peripheral neuropathy and liver involvement. They had more severe lung diseases and required lung biopsies more frequently. Patients in the middle-aged group exhibited the highest likelihood of severe anemia. Peripheral neuropathy was more common in this group than in younger patients, and their lung disease was less severe than in older patients but more severe than in younger patients. Young patients exhibited mild disease with the least severe lung involvement, mild anemia, and highest albumin levels. Baseline comorbidities and post-treatment adverse events increased significantly with age at diagnosis. Treatment strategies and efficacy were similar across groups, although older patients tended to receive lower initial doses of cyclophosphamide and corticosteroids. Conclusions: Age at diagnosis influenced GPA clinical characteristics. While the treatment did not vary significantly by age at onset, tailoring therapy to a patient's age is crucial to optimize outcomes and minimize complications.