Henoch-Schönlein Purpura Nephritis: Understanding the Six Clinical Pathological Types
Henoch-Schönlein purpura nephritis (HSPN) is a form of secondary glomerulonephritis that arises as a complication of Henoch-Schönlein purpura, an immune-mediated small vessel vasculitis. It primarily affects children but can also occur in adults. The classification of HSPN plays a crucial role in determining prognosis and guiding treatment strategies. Based on histopathological findings from kidney biopsies, HSPN is categorized into six distinct types, each reflecting the severity and extent of renal involvement.
Type I: Minimal Glomerular Abnormality
Type I HSPN represents the mildest form of kidney involvement. In this category, microscopic examination of the renal tissue reveals only subtle or minimal changes in the glomeruli, with no significant inflammation or structural damage. Patients often present with mild hematuria or proteinuria, and the long-term renal outlook is generally excellent. Most individuals in this group do not require aggressive therapy and are managed conservatively with regular monitoring.
Type II: Mesangial Proliferative Glomerulonephritis
This type is characterized by isolated mesangial proliferation, which may be either focal (affecting only some glomeruli) or diffuse (involving most glomeruli). While there is increased cellularity in the mesangial regions, there is no crescent formation or capillary wall damage. Clinically, patients may exhibit isolated microscopic hematuria or mild proteinuria. Type II typically carries a favorable prognosis, though ongoing follow-up is recommended to detect any progression.
Type III: Focal and Diffuse Mesangial Proliferation with Crescents (Less than 50%)
In Type III HSPN, kidney biopsy shows more pronounced mesangial proliferation along with the development of cellular crescents in fewer than 50% of glomeruli. Crescents are formed when inflammatory cells and fibrin infiltrate Bowman's space, indicating a more active disease process. This stage often correlates with more noticeable symptoms such as nephritic syndrome—characterized by hematuria, hypertension, and reduced kidney function. Immunosuppressive therapy may be considered depending on clinical presentation.
Prognostic Implications of Type III
Although the renal outcome for Type III is generally good, a subset of patients may experience persistent proteinuria or gradual decline in kidney function. Early intervention with corticosteroids or other immunomodulatory agents can help reduce inflammation and preserve renal health.
Type IV: Crescentic Involvement in 50–75% of Glomeruli
Type IV indicates moderate-to-severe disease, with crescent formation observed in 50% to 75% of glomeruli, alongside widespread mesangial proliferation. These patients frequently present with nephrotic-range proteinuria, hypertension, and impaired renal function. Due to the extensive glomerular injury, this subtype requires prompt and aggressive treatment, often including corticosteroids, cyclophosphamide, or rituximab in refractory cases.
Treatment Considerations for Type IV
Timely diagnosis and multidisciplinary management are essential. Long-term outcomes depend heavily on the speed of therapeutic intervention and patient adherence to follow-up care. Some individuals may progress to chronic kidney disease if left untreated.
Type V: Severe Crescentic Glomerulonephritis (>75% Involvement)
Type V HSPN represents the most severe histological pattern, with crescents affecting more than 75% of glomeruli. This form is associated with rapidly progressive glomerulonephritis (RPGN), leading to acute kidney injury in many cases. Symptoms include severe proteinuria, gross hematuria, edema, and significantly reduced glomerular filtration rate (GFR).
Urgent Intervention Required
Patients with Type V often require hospitalization and intensive therapy, including high-dose corticosteroids, plasma exchange, and cytotoxic agents. Despite treatment, some may develop end-stage renal disease (ESRD), highlighting the importance of early recognition and aggressive management.
Type VI: Pseudomembranoproliferative Glomerulonephritis Pattern
Type VI is a rare variant where the histological appearance mimics membranoproliferative glomerulonephritis (MPGN). This includes features like double contouring of the glomerular basement membrane due to mesangial interposition, along with mesangial proliferation. The clinical course can vary, but it often presents with significant proteinuria and signs of nephrotic syndrome.
Differential Diagnosis and Management
Because of its resemblance to primary MPGN, accurate diagnosis through immunofluorescence and electron microscopy is critical. Treatment usually involves immunosuppression tailored to disease activity, and long-term monitoring is necessary to prevent complications such as chronic kidney disease.
In summary, the classification of Henoch-Schönlein purpura nephritis into six types provides a valuable framework for assessing disease severity, predicting outcomes, and personalizing treatment plans. From minimal abnormalities in Type I to the aggressive crescentic forms in Types IV and V, understanding these categories helps clinicians deliver timely and effective care. Ongoing research continues to refine diagnostic criteria and explore novel therapies to improve long-term renal survival.