Skin Findings from Subcutaneous Drug Injection
The hypopigmented scars resulting from subcutaneous injection of heroin and other illicit drugs are called "skin popping scars" or "atrophic scars secondary to skin popping." 1, 2
Clinical Terminology and Characteristics
"Skin popping" is the medical term for the practice of injecting illicit drugs subcutaneously rather than intravenously. 1, 3 The resulting scars have distinct characteristics:
- Hyperpigmented or hypopigmented, fibrotic, depressed, round papules and plaques that typically appear on the extremities 1
- Atrophic scars at injection sites are specifically documented as a stigmata of injection drug use, present in approximately 30.7% of injection drug users 2
- The scars may present as 40-60 or more individual lesions distributed across accessible body surfaces 1
Associated Stigmata of Injection Drug Use
Beyond the atrophic scars themselves, clinicians should recognize the constellation of findings associated with subcutaneous drug injection 2:
- Track marks and "sooting tattoos" (present in 93.1% of injection drug users) - these are linear hyperpigmented marks along veins from repeated injections 2
- Active skin ulcers (18.8% of cases) at injection sites 2
- Puffy hand syndrome (8.7% of cases) from chronic soft tissue inflammation 2
- Chronic suppurative skin infections at injection sites that can lead to serious systemic complications 3
Clinical Significance and Recognition
Recognition of skin popping scars is critical because they serve as important clinical clues for possible substance abuse and its complications. 1, 2 The presence of these lesions should prompt:
- Evaluation for infectious complications including skin and soft tissue infections, hepatitis C, and HIV 2, 3
- Assessment for AA amyloidosis in chronic users presenting with proteinuria or renal impairment, as chronic suppurative skin infections from skin popping can trigger secondary amyloidosis 3
- Screening for other substance use-related dermatological manifestations including pruritus (the most common finding overall), hyperhidrosis (30%), and oral involvement (48.5%) 2
Common Pitfall
The primary pitfall is failing to recognize these scars as indicators of substance use disorder, which delays appropriate screening for associated complications and prevents early intervention for both the dermatological sequelae and the underlying addiction 1, 2. Healthcare practitioners must maintain awareness that these distinctive atrophic, hypopigmented scars represent a specific pattern of drug administration that carries unique risks beyond those of intravenous drug use 3.