The article provides a comprehensive review of IgA vasculitis (Henoch-Schönlein purpura), covering its history, current classification, epidemiology, clinical presentation, diagnosis, and future research directions. IgA vasculitis, first described in 1837, is a systemic hypersensitivity vasculitis caused by immune complex deposition in small blood vessels, leading to non-thrombocytopenic purpura or urticaria. It is the most common cause of primary glomerulonephritis worldwide. The article highlights the importance of detecting IgA deposition in small blood vessels and renal glomeruli for diagnosis. It discusses the challenges in classifying and diagnosing the condition, emphasizing the need for standardized criteria and guidelines. The epidemiology of IgA vasculitis is outlined, with a focus on its prevalence in children and adults, and the role of genetic and environmental factors in disease susceptibility. The clinical presentation in both children and adults is described, including common symptoms such as palpable purpura, arthritis, abdominal pain, and renal involvement. The diagnostic criteria, including biopsy findings and immunohistochemical techniques, are detailed. The pathogenesis of IgA vasculitis is explored, involving immune complex deposition, complement activation, and genetic and environmental triggers. The article also addresses the unmet clinical needs and future research directions, including the identification of biomarkers and the development of improved diagnostic and therapeutic approaches.The article provides a comprehensive review of IgA vasculitis (Henoch-Schönlein purpura), covering its history, current classification, epidemiology, clinical presentation, diagnosis, and future research directions. IgA vasculitis, first described in 1837, is a systemic hypersensitivity vasculitis caused by immune complex deposition in small blood vessels, leading to non-thrombocytopenic purpura or urticaria. It is the most common cause of primary glomerulonephritis worldwide. The article highlights the importance of detecting IgA deposition in small blood vessels and renal glomeruli for diagnosis. It discusses the challenges in classifying and diagnosing the condition, emphasizing the need for standardized criteria and guidelines. The epidemiology of IgA vasculitis is outlined, with a focus on its prevalence in children and adults, and the role of genetic and environmental factors in disease susceptibility. The clinical presentation in both children and adults is described, including common symptoms such as palpable purpura, arthritis, abdominal pain, and renal involvement. The diagnostic criteria, including biopsy findings and immunohistochemical techniques, are detailed. The pathogenesis of IgA vasculitis is explored, involving immune complex deposition, complement activation, and genetic and environmental triggers. The article also addresses the unmet clinical needs and future research directions, including the identification of biomarkers and the development of improved diagnostic and therapeutic approaches.