Pyomyositis

Background

• Primary bacterial infection of skeletal muscle
• Also known as myositis tropicans, more common in tropical settings
• Temperate climates in immune compromised patients
• Mainly disease of children, age 2-5 most common

Clinical Features

• More commonly affects proximal lower extremity muscles
• First stage: localized muscle pain, low grade fevers, vague complaints
  • Localized muscle inflammation without abscess
• Second stage: Worsening pain, muscle swelling, fever, abscess formation
• Third stage: Infection dissemination, septic shock

Pathophysiology

• Transient bacteremia after blunt trauma to muscle group, or vigorous exercise
• Most commonly Staph aureus, followed by Strep pyogenes, pneumococcus, neisseria, haemophilus, yersinia, pseudomonas, klebsiella, and E. coli

Risk Factors

• DM
• HIV
• IVDU
• Renal failure
• Immunosuppression

Work-Up

• CBC
• Chem 10
• PT/PTT
• CK
• Lactate

Diagnosis

• CT extremity with contrast
• Ultrasound
• MRI, study of choice
• Surgical exploration is gold standard

Differential Diagnosis

Skin and Soft Tissue Infection

• Cellulitis
  • Hand cellulitis
  • Facial cellulitis
  • Orbital cellulitis
• Erysipelas
• Lymphangitis
• Folliculitis
• Hidradenitis suppurativa
• Skin abscess
  • Anorectal abscess
  • Bartholin gland abscess
  • Pilonidal abscess
  • Scrotal abscess
• Necrotizing soft tissue infections
  • Necrotizing fasciitis
  • Necrotizing myositis
  • Necrotizing cellulitis
  • Fournier's gangrene
• Mycobacterium marinum

Look-A-Likes

• Sporotrichosis
• Osteomyelitis
• Deep venous thrombosis
• Pyomyositis
• Purple glove syndrome
• Tuberculosis (tuberculous inflammation of the skin)
• Rhabdomyolysis

Treatment

• IV antibiotics alone for first stage
  • Vancomycin 15-20mg/kg IV q24 hr, ceftriaxone 1g IV q24 hr, clindamycin 600mg IV q8 hr
• Surgical debridement plus antibiotics for abscess
• IV fluids, pressors, airway management, rapid debridement for septic shock

Disposition

• Admit