A 38-Year-Old Female with Persistent Pain Months After Being Bitten

Differential Diagnosis

• Ewing sarcoma
• Gout
• Osteomyelitis
• Septic arthritis

Diagnosis

This patient was diagnosed with osteomyelitis of the proximal phalanx of the first digit (arrow). This is often a delayed presentation. Note the complex-appearing periosteal reaction overlying ulnar aspect proximal first phalanx with underlying coarseness of the trabecula and subtle cortical erosive changes.

Learnings/What to Look for

• Typical features of osteomyelitis include monoarticular involvement, predilection for a soft-tissue swelling, joint space narrowing, bone erosions, and periostitis
  • Multiple organisms are often cultured—human oral flora (Eikenella, group A Streptococcus, Fusobacterium, Peptostreptococcus, Prevotella, and Porphyromonas spp) and human skin flora (such as staphylococci and streptococci)
  • A ‘fight bite’ is a specific type of human bite wound, often occurring over the MCP joint

Pearls for Urgent Care Management

• Surgical consultation is indicated as osteomyelitis typically requires a prolonged course of antibiotics
• If the wound is from a fight bite (clenched fist injury) explore for tendon involvement and, if acute, prescribe prophylactic antibiotics starting with amoxicillin clavulanic acid

Acknowledgment: Image and case provided by Experity Teleradiology (www.experity.com/teleradiology).