VisualDx Answer: b) Necrotizing Fasciitis

Answer: The correct answer is necrotizing fasciitis (b).

Necrotizing fasciitis is a deep and often devastating bacterial infection that tracks along fascial planes and expands well beyond any outward cutaneous signs of infection. Necrotizing fasciitis can occur without a clear portal of entry, although predisposing risk factors include major penetrating trauma (e.g., crush injury, deep penetrating wound), minor non-penetrating trauma (e.g., muscle strain, sprain, or contusion), and breaches in the skin and mucosa (e.g., lacerations, vesicles, injection drug use, episiotomies, and other surgical wounds).

Vibrio cholera is associated with necrotizing fasciitis infections in cirrhotic patients with exposure to ingestion of raw oysters and with exposure of lacerations to salt water. Aeromonas hydrophila is part of the Vibrionaceae family and can cause necrotizing fasciitis in both immunocompromised and immunocompetent patients. Unlike V. vulnificus sepsis, where exposure is usually to seawater, in A. hydrophila, infection, contact with brackish water, soil, wood, or dirty ditches is typically the common exposure. Infections can follow any trauma, fracture, or injury where there was exposure to fresh water. Patients with necrotizing fasciitis are acutely ill. They are often thought to have an infection that is not responding to standard antibiotic therapy. There is commonly a paucity of cutaneous findings in the early course of the disease. Pain is out of proportion to physical findings. There may be associated skin necrosis and bullae formation. While necrotizing fasciitis most commonly involves the lower extremities, other sites may also be involved. Signs of systemic illness such as fever, lethargy, hypotension, and tachycardia are present; these may progress to multi-organ failure.

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