What is the management approach for a patient with Henoch-Schönlein Purpura (HSP) presenting with myoglobinemia due to muscle injury or rhabdomyolysis?

Management of HSP with Myoglobinemia

For a patient with Henoch-Schönlein Purpura presenting with myoglobinemia due to muscle injury or rhabdomyolysis, immediately initiate aggressive fluid resuscitation with isotonic saline (0.9% NaCl) at volumes of 3-6L per day for moderate cases or >6L per day for severe cases (CK >15,000 IU/L), while simultaneously monitoring for and treating the underlying HSP-related complications, particularly renal involvement. 1

Immediate Fluid Resuscitation

• Start crystalloid fluid resuscitation immediately with isotonic saline (0.9% NaCl) as the initial fluid of choice, avoiding hypotonic solutions like Ringer's lactate. 1
• For severe rhabdomyolysis (CK >15,000 IU/L), administer volumes greater than 6L of fluid resuscitation; for moderate cases, 3-6L per day is typically sufficient. 1
• Early initiation of fluid resuscitation is critical, as delayed treatment is associated with higher risk of acute kidney injury. 1

Critical Laboratory Monitoring

Obtain the following labs immediately and monitor serially:

• Creatine kinase (CK), serum creatinine, and complete electrolyte panel including potassium, calcium, phosphorus, and magnesium—hyperkalemia can lead to life-threatening cardiac arrhythmias. 1
• Urinalysis with microscopy looking for myoglobinuria (brown color, cloudiness, positive for blood without RBCs) and evidence of HSP nephritis (proteinuria, red blood cell casts, dysmorphic red blood cells). 1, 2
• Plasma myoglobin and repeat CK measurements, as CK peaks between 24-120 hours after the initial insult. 1
• BUN, serum creatinine, and complete blood count to assess renal function and rule out thrombocytopenia. 2
• Blood pressure measurement as hypertension may indicate more severe renal involvement in HSP. 2

Electrolyte Management

• Monitor potassium levels closely and correct hyperkalemia emergently, as it can precipitate life-threatening cardiac arrhythmias. 1
• Trend CK, creatinine, and electrolytes daily until CK is declining and renal function is stable. 1
• Perform arterial blood gas analysis to assess for metabolic acidosis, which commonly occurs in severe rhabdomyolysis. 1

HSP-Specific Renal Management

The dual pathology of rhabdomyolysis-induced acute kidney injury and HSP nephritis requires careful attention:

• If urinalysis shows persistent proteinuria or hematuria consistent with HSP nephritis, start ACE inhibitor or ARB therapy targeting proteinuria to <1 g/day/1.73 m². 2
• For persistent proteinuria >1 g/day per 1.73 m² after ACE inhibitor/ARB trial and GFR >50 ml/min per 1.73 m², consider a 6-month course of corticosteroid therapy. 2
• For crescentic HSP with nephrotic syndrome and/or deteriorating kidney function, treat with high-dose intravenous methylprednisolone plus cyclophosphamide, following the same protocol as crescentic IgA nephropathy. 2, 3

Pain Management

• Use acetaminophen (500-1000 mg) as the preferred initial analgesic, with a maximum daily dose of 4-6 grams, as it avoids nephrotoxic effects particularly problematic in patients already at high risk for acute kidney injury. 1
• Avoid all NSAIDs (ibuprofen, ketoprofen, diclofenac, naproxen, mefenamic acid) due to their gastrointestinal and renal toxicity. 1, 2
• Reserve opioids for severe muscle pain that does not respond adequately to acetaminophen; if GFR is <30 ml/min, use fentanyl or buprenorphine as the safest opioid choices. 1

Medication Review and Discontinuation

• Immediately discontinue any causative agents that may have triggered rhabdomyolysis, including statins, red yeast rice containing lovastatin, creatine monohydrate, wormwood oil, licorice, and Hydroxycut. 1
• Document all over-the-counter medications, herbal supplements, and performance-enhancing products. 1
• Ask about recreational drug use (cocaine, methamphetamine, ecstasy, ketamine, heroin) as potential triggers. 1

Compartment Syndrome Surveillance

Monitor for compartment syndrome, which can both cause and complicate rhabdomyolysis:

• Early signs include pain, tension, paresthesia, and paresis. 1
• Late signs (pulselessness and pallor) often indicate irreversible damage. 1
• Consider fasciotomy when compartment pressure exceeds 30 mmHg or when differential pressure (diastolic blood pressure – compartment pressure) is <30 mmHg. 1

HSP-Specific Systemic Management

• For joint pain and cutaneous symptoms, oral prednisone at 1-2 mg/kg daily for two weeks may be beneficial. 2, 4
• Monitor for gastrointestinal complications (intussusception, bleeding from terminal ileum), cardiac arrhythmias, and neurological complications, which are rare but can occur in severe HSP cases. 3
• Do not use corticosteroids prophylactically at HSP onset to prevent nephritis, as moderate quality evidence shows no benefit. 2

Common Pitfalls to Avoid

• Do not wait for creatinine to reach 1.5 mg/dL before initiating aggressive fluid resuscitation—this threshold is specific to cirrhotic patients with acute kidney injury and is not applicable to trauma-related or HSP-related rhabdomyolysis. 1
• Do not start corticosteroids too early for mild proteinuria without adequate trial of ACE inhibitor/ARB therapy in HSP nephritis. 2
• Do not underestimate the severity in adolescents and adults, who have worse prognosis and higher risk of complications than children. 2, 3, 4

Long-Term Monitoring

• Monitor for persistent hematuria and proteinuria for at least 6 months, as these may indicate ongoing HSP disease activity. 2, 5
• A normal urinalysis on day 7 has a 97% negative predictive value in predicting a normal renal outcome in HSP. 5
• Long-term prognosis depends on the severity of renal involvement; end-stage renal disease occurs in 1-5% of patients with HSP. 4