Evolution of IgA nephropathy into anaphylactoid purpura in six cases-further evidence that IgA nephropathy and Henoch-Schonlein purpura nephritis share common pathogenesis

Background As the morphological and immunohistochemical manifestations of immunoglobulin A (IgA) nephropathy and Henoch-Schonlein purpura nephritis (HSPN) are very similar, they are considered to share a common pathogenesis. Although HSPN usually develops after the appearance of anaphylactoid purpura, we have encountered patients whose renal symptoms preceded purpura. Methods We reviewed the clinical courses of patients who were first diagnosed with IgA nephropathy, but developed purpura later, at the National Center for Child Health and Development in Tokyo, Japan. Results Of the 53 patients who were diagnosed with primary IgA nephropathy at our institute during the study period (March 2002 to July 2015), six (11 %) developed anaphylactoid purpura after the diagnosis of primary IgA nephropathy and therefore met the inclusion criteria. Duration between the onset of nephritis and subsequent appearance of purpura ranged from 5 months to 14 years. One patient reached end-stage renal failure due to IgA nephropathy and developed purpura after renal transplantation. All renal biopsies performed before the appearance of purpura showed mesangial proliferation with predominant IgA deposits. Urinary findings deteriorated in three patients after the appearance of purpura, including one patient who developed rapidly progressive glomerulonephritis. Renal biopsy findings worsened in two patients. At the last observation, two patients showed mild renal insufficiency. Conclusions Our clinical experience and previous reports support the argument that IgA nephropathy and HSPN are different manifestations of a single disease. Hence, it is acceptable to consider that they are variants of a single disease.