What is HSP (Henoch-Schönlein Purpura)?

What is HSP (Henoch-Schönlein Purpura)?

HSP is an IgA-mediated systemic small-vessel vasculitis that predominantly affects children and presents with a characteristic tetrad of palpable purpura, arthritis/arthralgia, abdominal pain, and renal involvement. 1

Definition and Epidemiology

HSP, also known as IgA vasculitis, is the most common form of systemic vasculitis in children, with a global incidence of 10 to 20 cases per 100,000 children per year. 2 Approximately 90% of cases occur in children between 2 and 10 years of age, with peak incidence at 4 to 7 years. 2 The condition is related to immunoglobulin A (IgA) antibody deposition in small blood vessels. 3

Clinical Presentation

The diagnosis can be made clinically when palpable purpura is present plus at least one of the following: renal involvement (hematuria and/or proteinuria), arthralgia/arthritis, or abdominal pain. 1

Key Clinical Features:

• Skin manifestations: Non-blanching purpuric rash, typically in the lower extremities and buttocks 3, 4
• Joint involvement: Arthritis or arthralgia, commonly affecting ankles and knees 4, 2
• Gastrointestinal symptoms: Diffuse abdominal pain, which may be accompanied by gastrointestinal bleeding 4, 2
• Renal involvement: Hematuria and/or proteinuria, with potential for glomerulonephritis 1, 3

Pathophysiology

The underlying mechanism involves IgA1 antibody deposition in small blood vessels, leading to leukocytoclastic vasculitis. 5 This process is accompanied by complement activation, cytokine release, and abnormal coagulation that contribute to vessel wall damage. 5 The characteristic finding on biopsy is predominant IgA deposition in affected tissues. 2

Diagnostic Approach

Essential initial workup includes:

• Urinalysis with microscopy to assess for glomerulonephritis, specifically looking for proteinuria, red blood cell casts, and dysmorphic red blood cells 1
• Basic metabolic panel including BUN, serum creatinine, and complete blood count with platelets to assess renal function and rule out thrombocytopenia 1
• Blood pressure measurement as hypertension may indicate more severe renal involvement 1

Renal ultrasound is the preferred initial imaging modality to assess kidney size and anatomy, particularly if renal biopsy is being considered for severe nephritis. 1

Clinical Course and Prognosis

Most cases are self-limited with an average disease duration of 4 weeks. 2 However, the various manifestations may present at any stage during the illness and can mimic other disease processes. 4 Renal involvement is the most important prognostic factor in determining long-term morbidity and mortality. 2

Potential Complications:

• Renal: Persistent proteinuria, crescentic glomerulonephritis, progression to end-stage renal disease 3, 2
• Gastrointestinal: Intussusception, gastritis, duodenitis, ileitis, ulcers, and severe GI bleeding 3, 4
• Neurological (rare): Headaches, behavioral changes, seizures (occurring in 53% of those with neurologic complications), posterior reversible encephalopathy syndrome 6
• Cardiac (exceptionally rare): Arrhythmias including atrial fibrillation and ventricular tachycardia 3

Management Principles

General Supportive Care:

Most cases require only supportive measures as HSP is usually a self-limiting disease. 6, 2 Current evidence does not support universal treatment with corticosteroids. 2

Specific Indications for Treatment:

• For severe gastrointestinal pain and hemorrhage: Oral prednisone at 1-2 mg/kg daily for two weeks may be beneficial 1, 2
• For persistent purpura and pain: Colchicine (1 mg/day) may be considered for at least six months 1
• Prophylactic corticosteroids are NOT recommended to prevent HSP nephritis, as moderate quality evidence shows no benefit 1

Renal Disease Management:

For persistent proteinuria, ACE inhibitors or ARBs are recommended as first-line therapy. 1 The target is proteinuria <1 g/day/1.73 m² rather than complete normalization. 1

For persistent proteinuria >1 g/day per 1.73 m² after ACE inhibitor/ARB trial and GFR >50 ml/min per 1.73 m², a 6-month course of corticosteroid therapy is suggested. 1

For crescentic HSP with nephrotic syndrome and/or deteriorating kidney function, treatment with high-dose intravenous methylprednisolone plus cyclophosphamide is recommended, following the same protocol as crescentic IgA nephropathy. 1, 3

Important Clinical Pitfalls

• Do not start corticosteroids too early for mild proteinuria without adequate trial of ACE inhibitor/ARB therapy 1
• Do not use NSAIDs like ketorolac (Toradol) in HSP patients, especially those with renal involvement, as they can cause acute kidney injury; acetaminophen is the safer first-line analgesic 1
• Monitor closely for renal involvement with serial urinalysis, as persistent hematuria and proteinuria indicate ongoing disease activity 1
• Be aware that neurological and cardiac complications, though rare, can occur and require prompt recognition and treatment 3, 6