What are the diagnostic criteria and management options for a child or young adult with suspected Henoch-Schönlein Purpura (HSP), particularly after a recent upper respiratory tract infection?

Diagnostic Criteria for Henoch-Schönlein Purpura (HSP)

The diagnosis of HSP requires palpable purpura (without thrombocytopenia) plus at least one of the following: abdominal pain, IgA deposition on biopsy, arthritis/arthralgia, or renal involvement. 1, 2

Clinical Presentation

Essential Feature

• Palpable purpura is present in 100% of cases and is the sine qua non for diagnosis—this non-thrombocytopenic rash typically appears on dependent areas (lower extremities and buttocks) 1, 3

Additional Manifestations (at least one required)

• Arthritis or arthralgia occurs in 75% of patients, typically affecting knees and ankles with migratory polyarthralgias 1, 4
• Abdominal pain develops in 60-65% of cases, characteristically periumbilical or epigastric, worsening with meals due to bowel angina 1, 2
• Renal disease manifests in 40-50% of patients as hematuria and/or proteinuria 1

Temporal Pattern

• More than 90% of patients have an antecedent upper respiratory infection within 1-3 weeks before symptom onset 1
• The various manifestations may present at any stage during the illness, not necessarily simultaneously, which can complicate early diagnosis 3

Diagnostic Workup

Laboratory Investigations

• Check complete blood count to confirm normal platelet count—this distinguishes HSP from thrombocytopenic purpura 1, 5
• Urinalysis is mandatory to detect hematuria and proteinuria indicating renal involvement 1, 5
• Serum creatinine and blood pressure monitoring should be performed to assess renal function 1
• Stool guaiac testing to detect occult gastrointestinal bleeding 2

Imaging Studies

• Abdominal ultrasound is recommended as the first diagnostic test when abdominal symptoms are present, as it can detect intussusception (the most common surgical complication) and bowel wall thickening 2
• CT scan may show asymmetric bowel wall thickening mainly involving jejunum and ileum if ultrasound is inconclusive 2

Histopathology (when needed for diagnostic certainty)

• Skin biopsy demonstrates leukocytoclastic vasculitis with IgA deposition in vessel walls, which increases diagnostic sensitivity and specificity 2, 5
• Renal biopsy shows IgA-immune deposits in glomeruli when renal involvement is severe or atypical 5
• Intestinal biopsies reveal IgA deposition and leukocytoclastic vasculitis in submucosal vessels, though superficial biopsies may only show inflammation and hemorrhage 2

Age-Related Considerations

• Over 90% of HSP cases occur in children younger than 10 years, making this primarily a pediatric diagnosis 1
• Adults with HSP are more likely to experience complications including severe renal disease and require closer monitoring 1

Management Approach

Supportive Care (Primary Intervention)

• Supportive treatment is the primary intervention since HSP spontaneously resolves in 94% of children and 89% of adults 1
• Adequate hydration, rest, and analgesics for joint pain are the mainstays of conservative management 1

Corticosteroid Therapy

• Oral prednisone 1-2 mg/kg daily for two weeks should be used for significant abdominal pain and joint symptoms 1
• A meta-analysis demonstrated that corticosteroid use in children reduced the mean time to resolution of abdominal pain and decreased the odds of developing persistent renal disease 1

Severe Renal Involvement

• Early aggressive therapy with high-dose steroids plus immunosuppressants is recommended for patients with severe renal involvement (nephrotic-range proteinuria, rapidly progressive glomerulonephritis, or crescentic disease) 1

Prognosis and Follow-up

• Long-term prognosis depends on the severity of renal involvement, with end-stage renal disease occurring in 1-5% of patients 1
• All patients require urinalysis monitoring for at least 6 months to detect delayed renal complications 1

Critical Pitfalls to Avoid

• Do not dismiss the diagnosis if the rash has not yet appeared—abdominal pain, arthritis, or renal symptoms may precede the characteristic purpura by days 3, 4
• Do not confuse HSP with thrombocytopenic purpura—always verify normal platelet count 1, 5
• Do not miss intussusception—maintain high suspicion in patients with severe, colicky abdominal pain and obtain urgent ultrasound 2
• HSP may coexist with or mimic Crohn's disease, particularly when gastrointestinal symptoms predominate 2