Objective: Immunoglobulin A vasculitis/Henoch-Schonlein purpura (IgAV/HSP) is a systemic vasculitis involving small vessels with the deposition of immune complexes containing IgA. It is the most common primary systemic vasculitis of childhood and is much less common in adults. Our aim was to investigate the differences and similarities between adult and paediatric patients with IgAV/HSP. Method: We retrospectively evaluated the medical records of 35 adult and 159 paediatric (< 18 years old) patients with a clinical diagnosis of IgAV/HSP who were seen at the Departments of Rheumatology and Pediatric Rheumatology, Hacettepe University, Ankara, Turkey. The paediatric and adult patients were classified with IgAV/HSP according to the Ankara 2008 and American College of Rheumatology 1990 criteria, respectively. Results: Upper respiratory tract infection was a common predisposing factor for both adults (34.3%) and children (21.4%). Creatinine and C-reactive protein were higher; and skin biopsy, hypertension, renal involvement, haematuria, proteinuria, and renal insufficiency at diagnosis were more frequent in adults than in children. Thrombocyte count was higher in children than in adults. Follow-up without treatment and complete recovery were more frequent in children, while persistent haematuria, chronic renal failure, relapse, and the use of corticosteroids/azathioprine were more frequent in adults. The only independent predictive factor for relapse was persistent haematuria. Conclusion: Various clinical and laboratory characteristics differ between children and adults with IgAV/HSP. Overall, IgAV/HSP has a self-limiting course in children but represents a more severe form of disease in adults, with more severe renal involvement. Persistent haematuria is a predictive factor for relapse.