What is the most likely diagnosis in a patient with significant opioid use disorder who has large ulcerative lesions on the anterior distal lower legs?

Xylazine-Induced Skin Ulceration

The most likely diagnosis is xylazine-induced skin ulceration, a rapidly emerging complication of contaminated opioid use, particularly in regions where fentanyl is mixed with xylazine (a veterinary sedative). This should be your primary consideration in any patient with opioid use disorder presenting with large, necrotic leg ulcers, especially if they are located on the anterior distal lower extremities 1.

Key Diagnostic Features

The clinical presentation is highly characteristic:

• Large, necrotic ulcers with extensive subcutaneous tissue involvement
• Bilateral lower extremity distribution (knees to ankles most commonly affected)
• Copious purulent drainage with foul odor
• Poor wound healing despite standard wound care
• Geographic clustering: Predominantly seen in Philadelphia and Puerto Rico where xylazine contamination of the drug supply reaches up to 78% 1

Pathophysiology

Xylazine causes direct alpha-2 adrenergic receptor-mediated vasoconstriction of local blood vessels, leading to:

• Decreased skin perfusion at injection sites
• Tissue ischemia and necrosis
• Impaired wound healing
• Secondary bacterial superinfection (commonly MRSA, Streptococcus pyogenes, E. coli, Proteus) 1

Critical Differential Considerations

While xylazine is the leading diagnosis in current practice, you must also consider:

Venous/Lymphatic Insufficiency from IV Drug Use

• Occurs in 74% of patients with intravenous drug addiction 2
• Presents with fibrinous, recurrent ulcers predominantly on legs (77% of cases spare the upper limbs) 2
• More chronic course (>1 year in 61.5% of cases) 2

Peripheral Artery Disease (PAD)

• Less likely in younger patients without traditional vascular risk factors
• Would expect ischemic rest pain and signs of arterial insufficiency 3
• Associated more with inhaled drug use than IV use 2

Management Approach

Immediate priorities:

1. Suspect xylazine contamination and counsel patient accordingly
2. Aggressive wound debridement of necrotic tissue 1
3. Broad-spectrum IV antibiotics targeting polymicrobial infection (cover MRSA, Streptococcus, gram-negatives) 1
4. Topical wound care with appropriate dressings 1
5. Substance use disorder treatment referral - withdrawal from contaminated supply is essential for healing 2, 4

Common Pitfalls

• Do not assume standard venous ulcer management will suffice - these wounds require recognition of the xylazine etiology
• Do not miss deep tissue involvement - check for osteomyelitis (tibial involvement reported) and abscess formation 1
• Do not overlook systemic effects - xylazine also causes hypotension, bradycardia, and respiratory depression beyond the local tissue damage 1
• Geographic awareness is critical - if practicing outside high-prevalence areas, xylazine may still be present as it spreads to new regions

The key distinguishing feature from traditional drug-related leg ulcers is the severity and rapidity of tissue necrosis with xylazine, compared to the more chronic fibrinous ulcers seen with venous insufficiency from long-term IV drug use 2, 1.