CHAPTER 6: Dermatology

BLISTERING DISORDERS

NECROTIZING FASCIITIS

An acute, rapidly progressive, necrotizing, life-threatening infection of the subcutaneous tissues, often associated with septic shock or Streptococcal toxic shock syndrome.

• Can be rapidly fatal if not recognized and treated promptly and appropriately

EPIDEMIOLOGY

• Rare in children; estimated 500–1500 cases per year in the United States

• Can be seen at any age, including neonates

• Most children with invasive Group A β-hemolytic Streptococcus (GABHS) infection are otherwise healthy; more than 50% of children with non-GABHS necrotizing fasciitis have at least one risk factor

• Risk factors: Antecedent varicella infection (with GABHS-related cases); recent surgery or trauma; intramuscular injection; chronic medical conditions (diabetes mellitus, malnutrition, obesity, immunosuppression). In neonates, circumcision, omphalitis, history of scalp electrode placement, necrotizing enterocolitis

ETIOLOGY

• Inoculation of bacteria into the subcutaneous tissues with resultant proliferation and release of destructive enzymes and exotoxins results in extensive tissue necrosis, thrombosis of blood vessels, and rapid progression along fascial planes

• Common: GABHS. Typically involves the groin or lower extremities

• Less common: Aerobic and non-aerobic organisms, including Staphylococcus aureus, anaerobic streptococci, group B Streptococcus, Proteus vulgaris, Escherichia coli, Pseudomonas aeruginosa, and Bacteroides fragilis. May be polymicrobial. Usually involves the abdominal wall, perianal or genital area, or a postoperative wound

DIFFERENTIAL DIAGNOSIS

• Cellulitis, erysipelas, pyoderma, staphylococcal scalded skin syndrome, toxic shock syndrome, burns

CLINICAL MANIFESTATIONS

• Initial symptoms may be nonspecific and include localized pain, fever, chills, vomiting, pharyngitis, malaise, altered mental status, and myalgias

• Skin manifestations are toxin-mediated, typically seen with GABHS-related necrotizing fasciitis, and present with erythematous ill-defined patch(es) or plaque(s)

• Associated signs and symptoms include severe pain out of proportion to clinical findings, extreme tenderness involving both affected and clinically unaffected areas, numbness, edema, and murky dishwater-like discharge

• Rapid progression to purpuric patch(es) or plaque(s) with or without blistering, followed by the development of ulceration and gangrene. Crepitus may be appreciated in non-GABHS-related necrotizing fasciitis

• Systemic toxicity that may include features of septic shock or, in the case of invasive GABHS, toxic shock syndrome with hypotension and multisystem organ failure

• Fournier’s gangrene: Involvement of the genital and perianal area; typically polymicrobial

DIAGNOSTICS

• Clinical diagnosis requires high level of suspicion

• Cultures of blood, wound, and deep tissue (incisional biopsy)

• Histology of incisional biopsy reveals tissue necrosis

• CBC: Leukocytosis

• CRP, ESR: Elevated

• Metabolic panel: Hyponatremia, elevated blood urea nitrogen, metabolic acidosis, hypocalcemia, elevated serum creatine phosphokinase

• Ultrasound may demonstrate fascial thickening and fluid collections

• MRI is more sensitive than CT but may overestimate involvement; a negative MRI can exclude necrotizing fasciitis

MANAGEMENT

• Prompt surgical consultation and surgical exploration with wide excision of necrotic tissue; delay results in higher mortality. Surgical reexploration and repeat ...