What Is Henoch-Schönlein Purpura Nephritis?
Henoch-Schönlein purpura nephritis (HSPN) is a form of kidney injury that develops as a complication of Henoch-Schönlein purpura (HSP), an autoimmune condition triggered by an abnormal immune response to infections, certain medications, or food allergens. Although it can affect people of all ages, HSP is most commonly seen in children, particularly between the ages of 2 and 6.
Understanding the Connection Between HSP and Kidney Damage
HSP is fundamentally a systemic vasculitis—an inflammation of the small blood vessels throughout the body. Because the kidneys are composed of a dense network of tiny capillaries responsible for filtering waste from the blood, they are especially vulnerable during episodes of widespread vascular inflammation.
When immune complexes—particularly those containing immunoglobulin A (IgA)—deposit in the glomeruli (the filtering units of the kidneys), they trigger local inflammation. This condition is known as IgA vasculitis with nephritic involvement, which manifests clinically as HSP nephritis.
Symptoms of Henoch-Schönlein Purpura Nephritis
The hallmark signs of HSP typically appear before kidney involvement and include:
- Purple-colored skin rash (palpable purpura), usually on the legs and buttocks
- Joint pain and swelling, especially in the knees and ankles
- Abdominal pain, sometimes accompanied by gastrointestinal bleeding
Kidney-related symptoms may develop days to weeks after the initial outbreak and can range from mild to severe. Common renal manifestations include:
- Hematuria (blood in the urine), often microscopic but sometimes visible
- Proteinuria (excess protein in the urine), which may cause foamy urine
- High blood pressure
- Reduced kidney function, potentially progressing to acute or chronic kidney failure in severe cases
Diagnosis and Medical Evaluation
To confirm HSP nephritis, doctors typically perform a combination of urine tests, blood work, and sometimes a kidney biopsy. Urinalysis often reveals red blood cells and protein, while serum creatinine levels help assess overall kidney performance.
A kidney biopsy is the gold standard for determining the extent of damage and guiding treatment decisions. The biopsy results are usually classified using histological scoring systems like the International Study of Kidney Disease in Children (ISKDC) classification.
Treatment Approaches and Management
Early intervention is crucial to prevent long-term kidney complications. Treatment strategies depend on the severity of kidney involvement:
Mild cases may only require supportive care, including hydration, blood pressure control, and monitoring. However, moderate to severe HSPN often necessitates pharmacological therapy. Common treatments include:
- Corticosteroids (such as prednisone) to reduce inflammation
- Immunosuppressive agents (like cyclophosphamide or mycophenolate mofetil) in aggressive cases
- Angiotensin-converting enzyme (ACE) inhibitors or ARBs to manage proteinuria and protect kidney function
In rare instances where renal function deteriorates rapidly, more intensive therapies such as plasma exchange or biologic agents may be considered.
Prognosis and Long-Term Outlook
The majority of children with HSP recover fully without lasting effects. However, approximately 30–50% of patients with significant kidney involvement may experience persistent urinary abnormalities, and a smaller subset could develop chronic kidney disease over time.
Regular follow-up with a nephrologist is essential, even after symptoms resolve, to monitor for late-onset complications and ensure optimal long-term outcomes.
While HSP nephritis can be concerning, timely diagnosis and appropriate management significantly improve prognosis. Awareness of early warning signs and prompt medical attention play key roles in minimizing kidney damage and supporting full recovery.