Speediatrics: Can you solve this quick case involving a lower-limb rash?

The next in our series of quick quizzes in paediatric care asks – what is the likely diagnosis in this case of a child with recent upper respiratory tract infection who has developed a rash?

The Case

A seven year old presents with a few days history of an upper respiratory tract infection and a mild fever, plus a rash on the lower limbs which has now been present for 48 hours.

Rash

This rash was present on both legs, but not elsewhere, and did not blanche

What’s the diagnosis?

SHOW THE ANSWER 〉

Fast Facts: Henoch Schonlein purpura

Clinical Features:

Classical Triad of Symptoms:
- Palpable purpura: Non-blanching, red or purple rash, typically over the buttocks and lower extremities. May extend to the arms, face, and trunk.
- Arthritis/Arthralgia: Often migratory, affecting large joints (knees, ankles). Usually non-deforming and self-limiting.
- Abdominal Pain: Colicky, diffuse pain, often accompanied by nausea, vomiting, or gastrointestinal bleeding (may present as blood in stools).
Renal Involvement:
- Haematuria, proteinuria, or nephritic syndrome (develops in up to 50% of cases).
- Renal disease typically occurs within the first 6 weeks but can present later.
Other Symptoms:
- Scrotal pain or swelling in boys.
- Rarely, neurological symptoms (headache, seizures).

Epidemiology:

Age Group:
- Most commonly affects children aged 3–10 years.
- Peak incidence is around 5 years of age.
Gender Predilection:
- Slight male predominance (2:1).
Seasonality:
- More common in autumn and winter, often following upper respiratory tract infections.

Diagnosis:

Clinical Diagnosis:
- Based primarily on the characteristic rash (palpable purpura), often in association with joint, gastrointestinal, or renal symptoms.
Supporting Investigations:
- Urinalysis: Check for haematuria and proteinuria to assess renal involvement.
- Blood tests: Normal platelet count (to differentiate from thrombocytopenic purpura), normal or elevated ESR/CRP, and possible elevated serum creatinine in renal involvement.
- Skin biopsy (rarely required): If diagnosis is unclear, may show leukocytoclastic vasculitis with IgA deposits.

Differential Diagnosis:

Idiopathic Thrombocytopenic Purpura (ITP):
- Presents with purpura, but without joint, renal, or gastrointestinal involvement.
- Platelet count is low, unlike HSP.
Systemic Lupus Erythematosus (SLE):
- May have a similar rash and renal involvement, but often has additional features (e.g., photosensitivity, malar rash, systemic symptoms).
Kawasaki Disease:
- Distinguished by persistent fever, conjunctivitis, mucosal changes, and extremity changes.
- Coronary artery involvement rather than renal or gastrointestinal symptoms.
Meningococcal Septicemia:
- Purpuric rash often associated with fever and signs of sepsis (e.g., hypotension, altered consciousness).
- Immediate medical emergency.

Red Flags:

Severe Abdominal Pain:
- Intussusception or bowel ischemia must be considered in cases of acute, severe abdominal pain.
Signs of Nephritis/Nephrotic Syndrome:
- Rising blood pressure, decreased urine output, or significant proteinuria/haematuria may indicate more severe renal involvement requiring urgent nephrology referral.

Management:

General Approach:
- Largely supportive care as HSP is typically self-limiting (lasting 4-6 weeks).
- Encourage rest and hydration.
- Analgesia (e.g., paracetamol or ibuprofen) for joint pain and abdominal discomfort.
Steroids:
- Considered in severe cases, especially with significant abdominal pain, nephritis, or scrotal involvement.
Monitoring Renal Function:
- Regular urinalysis and blood pressure checks for 6 months post-diagnosis to monitor for delayed renal involvement.
- Prompt referral to a paediatric nephrologist if signs of nephritis or nephrotic syndrome develop.
Hospital Admission:
- Indicated for severe gastrointestinal symptoms (e.g., intussusception), significant renal involvement, or inability to manage pain or hydration at home.

Patient Education:

Course of Illness:
- Reassure that the condition is self-limiting in most cases, resolving within 4-6 weeks.
Recognizing Complications:
- Educate parents on signs of complications (e.g., worsening abdominal pain, blood in urine, or scrotal swelling), and advise seeking immediate medical attention if these occur.
Renal Monitoring:
- Emphasize the importance of regular follow-up appointments to monitor kidney function for several months after recovery.
Recurrence:
- Recurrence of symptoms can happen in about 30% of cases, typically within the first few months. Educate parents on recognizing early signs of a recurrence.