What are the signs of factitious dermatitis pathology?

Signs of Factitious Dermatitis (Dermatitis Artefacta) on Pathology

Factitious dermatitis is primarily a clinical diagnosis of exclusion with no specific pathological findings—the key pathological feature is the absence of findings that would suggest an alternative organic dermatological disease. 1, 2

Primary Pathological Characteristics

The histopathology in dermatitis artefacta is typically non-specific and reflects the method of self-injury rather than a distinct disease process. 2 The pathological findings depend entirely on what mechanism the patient used to create the lesions (mechanical trauma, chemical application, thermal injury, etc.). 3, 4

Non-Specific Findings Include:

• Epidermal necrosis or ulceration without underlying vasculitis, infection, or inflammatory infiltrate that would suggest organic disease 3
• Acute inflammatory changes consistent with recent trauma but lacking the organized pattern seen in true inflammatory dermatoses 3
• Absence of specific diagnostic features for conditions like vasculitis, bullous diseases, or infectious processes that the clinical presentation might mimic 2
• Normal tissue architecture in areas adjacent to the lesions, which contrasts with most organic skin diseases that show transitional changes 1

Critical Diagnostic Approach

The role of biopsy in factitious dermatitis is to exclude organic disease, not to confirm the diagnosis. 2 The pathologist should specifically look for:

• Absence of vasculitis in ulcerated or necrotic lesions 2
• Absence of specific immunofluorescence patterns that would indicate autoimmune blistering diseases 2
• Absence of organisms on special stains (PAS, GMS, acid-fast) that would indicate infection 2
• Absence of granulomatous inflammation or other organized inflammatory patterns 3

Clinical-Pathological Correlation

Multiple biopsies showing different non-specific patterns in the same patient strongly suggests factitious disease. 3 Key correlative features include:

• Geometric or bizarre-shaped lesions on clinical examination that don't follow anatomical or dermatomal distributions 3, 2
• Sharp demarcation between affected and normal skin without the gradual transition typical of organic disease 3
• Lesions in easily reachable areas while sparing areas the patient cannot access (the "hollow hand sign"—sparing of the center of the back) 1, 2
• Presence of multiple morphologies (erosions, ulcers, crusts, burns) suggesting different methods of self-injury 3

Common Pitfalls to Avoid

Do not rely on pathology alone to make or exclude the diagnosis of factitious dermatitis. 2 Critical mistakes include:

• Assuming a non-specific biopsy rules out organic disease—always correlate with clinical presentation and consider additional testing 2
• Missing concomitant organic disease—patients with factitious dermatitis may also have legitimate dermatological conditions 1
• Failing to recognize chemical-induced changes—application of caustic substances can create unusual histological patterns that may be misinterpreted 4
• Over-interpreting artifact—crush artifact from biopsy technique should not be confused with pathological findings 3

Specific Histological Patterns by Method of Injury

The pathology reflects the mechanism used:

• Mechanical trauma (scratching, cutting): Non-specific ulceration with acute inflammation and granulation tissue 3
• Chemical application: Epidermal necrosis with variable dermal inflammation depending on the agent used 4
• Thermal injury: Coagulative necrosis of epidermis and superficial dermis 3
• Excoriation: Erosions with serum crusts and absence of primary lesions 3

In 93% of successfully managed cases, diagnosis required multidisciplinary evaluation combining dermatological assessment (including biopsy to exclude organic disease) with psychiatric evaluation. 1