Henoch-Schönlein Purpura Nephritis: Diagnosis, Clinical Features, and Differential Considerations

Henoch-Schönlein purpura nephritis (HSPN) is a systemic vasculitic disorder that primarily affects small blood vessels and often involves the kidneys. It is considered a post-infectious immune complex-mediated disease, typically occurring in children but also seen in adults. Early and accurate diagnosis is crucial to prevent long-term renal complications and ensure appropriate management.

Key Diagnostic Criteria for HSPN

The diagnosis of Henoch-Schönlein purpura nephritis is based on a combination of clinical manifestations, laboratory findings, and histopathological evidence. The following features are essential for establishing the diagnosis:

1. Characteristic Skin Purpura

The hallmark of HSPN is palpable purpura, which usually appears symmetrically on the lower extremities or all four limbs. These non-blanching skin lesions result from leukocytoclastic vasculitis affecting dermal capillaries. Importantly, thrombocytopenia is absent—platelet counts remain within normal range, helping differentiate it from other bleeding disorders.

2. Extrarenal Manifestations

In addition to skin involvement, patients may present with gastrointestinal symptoms such as abdominal pain, nausea, vomiting, or even gastrointestinal bleeding due to vasculitis in the intestinal tract. Arthralgia or arthritis, particularly affecting large joints like knees and ankles, is also commonly observed. These multi-system features support the diagnosis when combined with renal signs.

3. Renal Involvement During or After Acute Phase

Renal manifestations typically develop during the active phase of the disease or shortly after the resolution of skin purpura. Common urinary abnormalities include hematuria (either gross or microscopic), proteinuria, and the presence of cellular casts in urine sediment. The onset of these findings confirms the progression to HSP nephritis and warrants further evaluation.

Pathological Findings and Comparison with IgA Nephropathy

Histologically, HSPN closely resembles IgA nephropathy, both showing dominant IgA deposits in the mesangial areas of glomeruli. However, HSPN often presents with more severe vascular damage, including capillary loop necrosis and prominent fibrin deposition. These pathological differences may correlate with a potentially more aggressive clinical course and emphasize the need for kidney biopsy in atypical or severe cases.

Differential Diagnosis: Conditions to Rule Out

Accurate diagnosis requires excluding other systemic diseases that mimic HSPN. Key differential diagnoses include:

• ANCA-associated vasculitis (small vessel vasculitis): Presents with similar renal and skin findings but typically shows positive ANCA antibodies and lacks the characteristic rash distribution of HSP.
• Antiphospholipid antibody syndrome (APS): May cause thrombotic events and skin lesions but is associated with recurrent thrombosis, pregnancy morbidity, and specific autoantibodies.
• Sepsis-induced vasculopathy: Can lead to purpuric rashes and organ dysfunction but occurs in the context of infection and systemic inflammatory response.
• Allergic vasculitis (hypersensitivity vasculitis): Often drug-induced and lacks the full spectrum of HSP features.
• Systemic lupus erythematosus (SLE): Lupus nephritis can resemble HSPN, but SLE patients usually have positive ANA, anti-dsDNA antibodies, and multi-organ involvement beyond the typical HSP pattern.

Clinical Remission and Prognostic Indicators

Successful treatment is measured by sustained clinical remission. The accepted criteria for recovery include complete resolution of symptoms—such as hematuria, proteinuria, and systemic manifestations—with no relapse for at least six months. Regular follow-up with urinalysis and blood pressure monitoring is recommended, especially in patients who had moderate to severe renal involvement initially.

While many pediatric cases resolve spontaneously, adult-onset HSPN tends to carry a higher risk of chronic kidney disease. Therefore, early recognition, precise diagnosis, and individualized management strategies are vital to improving long-term outcomes.