What is the differential diagnosis and management for forearm swelling and burning?

Differential Diagnosis for Forearm Swelling and Burning

The most critical immediate concern is acute compartment syndrome, which requires urgent surgical decompression within hours to prevent permanent tissue necrosis and functional disability.

Life-Threatening Conditions Requiring Immediate Action

Compartment Syndrome

• Circumferential burns causing compartment syndrome present with swelling, burning pain, and can lead to acute limb ischemia with neurological disorders and downstream necrosis 1
• Look for blue, purple, or pale extremities indicating poor perfusion—this requires emergency escharotomy within 48 hours of circulatory impairment 2
• Spontaneous bilateral compartment syndrome can occur without trauma, presenting with severe pain, swelling, decreased range of motion, and numbness in all fingers 3
• Measure compartment pressures immediately if suspected; do not wait for pulse loss as pulses may remain palpable until late stages 3

Thermal Burns with Eschar Formation

• Deep partial-thickness or full-thickness circumferential burns increase intra-compartmental pressure 1
• Escharotomy should be performed only at a burn center due to high complication risks including hemorrhage and infection 1
• If transfer is impossible, obtain specialist telemedicine consultation before attempting escharotomy 1

Infectious Etiologies

Deep Soft Tissue Infections

• Mycobacterium tuberculosis can cause extensive forearm infection with recurrent swelling, particularly in patients with history of pulmonary TB or immunocompromise 4
• Presents with progressive swelling, may show bone erosion on x-ray, and requires anti-tuberculosis therapy 4
• Fungal phaeohyphomycosis (Exophiala jeanselmei) can present as subcutaneous swelling adjacent to old burn scars, requiring surgical excision 5

Necrotizing Soft Tissue Infection

• Consider in rapidly progressive swelling with systemic toxicity
• Requires urgent surgical debridement

Vascular Injuries

Arterial Laceration or Thrombosis

• Penetrating trauma causing radial or ulnar artery injury presents with swelling and may have intact distal pulses if one artery remains patent 6
• Direct digital pressure and compressive dressings achieve hemostasis in most cases; emergent operative exploration is not routinely warranted unless critical ischemia is present 6
• Assess palmar arch circulation—one intact forearm artery is adequate for hand viability if palmar arch is intact 6

Thromboembolism

• Can cause spontaneous compartment syndrome without trauma 3
• Obtain vascular ultrasound to exclude arterial or venous thrombosis

Musculotendinous Injuries

Muscle Strain or Contusion

• Generally self-limited conditions responding to rest, splinting, elevation, and analgesics 7
• Avoid injudicious use of heat, cold, or electrical modalities 7

Diagnostic Approach Algorithm

1. Immediate assessment for compartment syndrome:

   • Palpate compartments for tightness
   • Assess for pain out of proportion to examination
   • Check distal neurovascular status (pulses, capillary refill, sensation, motor function)
   • Measure compartment pressures if available
   • If suspected, proceed directly to surgical decompression—do not delay 1

2. Evaluate for burn injury:

   • Assess burn depth and circumferential involvement
   • Calculate TBSA using Lund-Browder chart 8
   • Any partial-thickness or full-thickness hand/forearm burn requires immediate burn specialist referral 2

3. Rule out infection:

   • Obtain x-ray to assess for osteomyelitis or gas in soft tissues 4
   • Consider aspiration for culture if abscess suspected 5
   • Check TB risk factors and obtain appropriate cultures if chronic/recurrent presentation 4

4. Assess for vascular injury:

   • Document history of trauma
   • Perform Allen test to assess palmar arch patency 6
   • Obtain vascular ultrasound if pulses diminished or absent 3

Critical Management Pitfalls to Avoid

• Never delay compartment syndrome decompression waiting for pulse loss—irreversible damage occurs within 6-8 hours 1
• Do not perform escharotomy outside a burn center unless absolutely unavoidable; poorly performed escharotomy increases morbidity 1
• Do not assume isolated arterial injury requires emergent operative repair; conservative hemostasis is appropriate if hand remains well-perfused 6
• Do not dismiss recurrent swelling as benign—consider atypical infections like TB, especially with risk factors 4
• Avoid routine prophylactic antibiotics for simple soft tissue injuries; reserve for clinically evident infections 2