At risk: IV drug abuse, HIV, sickle cell disease, diabetes, peripheral vascular disease, immunocompromised, cancer, alcoholism, organ transplants

1. Cellulitis
   = acute infection of dermis + SQ tissue
   • pain, erythema, edema, warmth
   
   CT:
   • skin thickening
   • septation of SQ fat
   • thickening of underlying superficial fascia
   
   Dx: clinical assessment
   DDx: heart failure
2. Necrotizing fasciitis
3. Soft-tissue abscess
   • Cause: methicillin-resistant S. aureus (MRSA, 51%)
   • well-demarcated fluid collection with peripheral pseudo-capsule showing rim enhancement
   • DDx: cellulitis, fasciitis (no rim enhancement)
4. Infectious myositis
5. Osteomyelitis
6. Septic arthritis
7. Septic bursitis