Sec 7 Disorders of Epidermal Differentiation and Keratinization Flashcards
How many percent of contact dermatitis is irritant?
80%
Most important exogenous factor for ICD
Inherent toxicity of chemical for human skin
Major risk factor for irritant hand dermatitis because of impaired barrier function and lower threshold for skin irritation
Atopic dermatitis
Mainstay of treatment for ICD
Identification and avoidance of potential irritant
Mechanisms of ICD:
- Removal of surface lipids and water-holding substances
- Damage to cell membranes
- Epidermal keratin denaturation
- Direct cytotoxic effects
Key cytokine in ICD leading to increased expression of major histocompatibility complex class II and intracellular adhesion molecule 1 on keratinocytes
Tumor Necrosis Alpha-1 (TNA-1)
Hones naive T-lymphocytes to the skin and is elevated during irritant reactions
CCL21
Upregulation of this plays a major role in the hardening phenomenon in cutaneous irritation
Ceramide 1 synthesis
Exogenous factors influencing cutaneous reaction
- Chemical properties 2. Characteristics of exposure 3. Environmental factors 4. Mechanical factors 5. UV radiation
A synergistic or antagonistic effect that occurs as a consequence of specific cellular interactions between compounds that would not occur when irritant is used alone
Crossover phenomenon
T or F: Visible skin irritation (erythema) is decreased in older persons while invisible skin irritation (barrier damage) is increased in elderly
True
Endogenous factors influencing cutaneous reaction
- Primary sensitive skin 2. Lack of hardening 3. Atopic dermatitis 4. Skin site 5. Skin permeability 6. Secondary hyperirritability of the skin (status eczematicus) 7. Individual (genetic) susceptibility
Sites more susceptible to ICD
Face Neck Scrotum Dorsal hands
T or F: A history of atopy is a well-known risk factor for ICD
True
Clinically presents as an acute, often multiple monomorphic reaction that includes scaling, low-grade erythema, vesicles or erosions usually on the dorsum of hands and finger
Irritant reaction
Results from a single skin exposure to a strong irritant or caustic chemical with sensation of burning, itching or stinging; heals after 4 weeks with good prognosis
Acute ICD
Acute reaction but without visible signs of inflammation until 8-24 hours or more after exposure; good prognosis
Delayed acute irritancy
Most frequent type of contact dermatitis in clinical practice; aka traumiterative ICD; with symptoms appearing after days, month or years; prognosis variable
Chronic cummulative ICD
Patients complain of itching, tingling, stinging, burning within minutes of contact with an irritant without visible cutaneous changes; usually on face, head and neck
Subjective irritancy
Irritation is not visually apparent but histologically apparent; common in use of surfactant
Suberythematous irritation
Mechanical irritation from repeated microtrauma and friction; usually leads to dry, hyperkeratotic abraded skin
Frictional dermatitis
Develop after acute skin trauma as burns or lacerations; most commonly on the hands; can persist for about 6 weeks or more; resembles nummular dermatitis
Traumatic dermatitis
Usually seen after exposure to oils, tars, heavy metals and halogens but also after use of cosmetics; pustules are sterile; seen is atopic and seborrheic patients
Pustular or acneiform reactions
Characterized by intense itching, dry skin and ichthyosiform scaling
Asteatotic irritant reaction