Henoch-Schönlein Purpura (HSP) is a systemic vasculitis mediated by IgA and characterized by the clinical triad of non-thrombocytopenic palpable purpura. Adults with HSP are more likely to have more severe disease compared to children. Causes and Risk Factors for Henoch-Schonlein Purpura. Henoch-Schönlein Purpura nephritis (HSPN) has been extensively studied in children but, its natural history in adults is much less known. Treatment and Course of Henoch-Schönlein Purpura; Living with HSP is more common in children than adults, but has a tendency to be more severe when it.