15.4 Dermatologic Conditions That Cause or Complicate Wounds
Key Takeaways
- Bullous pemphigoid causes tense blisters in older adults, sometimes triggered by DPP-4 inhibitors; perilesional direct immunofluorescence shows linear IgG and C3 along the basement membrane, and potent topical corticosteroids are first-line.
- Pemphigus vulgaris causes fragile flaccid blisters and painful mucosal erosions with a positive Nikolsky sign; biopsy shows intraepidermal acantholysis with intercellular IgG on direct immunofluorescence, and rituximab with corticosteroids is first-line for moderate to severe disease.
- Stevens-Johnson syndrome involves less than 10% body surface area detachment, overlap 10% to 30%, and toxic epidermal necrolysis more than 30%; stop the culprit drug (such as allopurinol, anticonvulsants, or sulfonamides), estimate mortality with SCORTEN, and treat in a burn or intensive care unit.
- Moisture-associated skin damage includes incontinence-associated dermatitis, intertriginous dermatitis, periwound moisture damage, and peristomal moisture damage; incontinence-associated dermatitis is diffuse with irregular edges in skin folds rather than centered over a bony prominence.
- The ISTAP classification grades skin tears as type 1 (no skin loss), type 2 (partial flap loss), or type 3 (total flap loss); realign the flap when viable, use nonadherent dressings, and mark an arrow showing the direction of removal.
15.4 Dermatologic Conditions That Cause or Complicate Wounds
Core Clinical Principle: Many "wounds" are skin diseases, and many skin diseases complicate wounds. Recognizing blistering disorders, drug reactions, moisture damage, skin tears, and inflammatory skin conditions prevents misclassification (such as calling incontinence dermatitis a pressure injury) and leads to the right biopsy and treatment.
The CWSP outline lists dermatological wounds under Etiological Considerations. Contact dermatitis and scarring are covered with complications, and pyoderma gangrenosum and vasculitis with inflammatory ulcers.
Autoimmune Blistering Diseases
| Feature | Bullous Pemphigoid | Pemphigus Vulgaris |
|---|---|---|
| Typical patient | Older adults, often over 70; associated with neurologic disease and drugs such as DPP-4 inhibitors (gliptins) | Middle-aged adults |
| Blisters | Tense, on red or normal skin; intense itch; may start as hives | Flaccid, fragile, rupture easily into painful erosions |
| Mucosa | Uncommon | Almost always involved (oral erosions) |
| Nikolsky sign | Negative | Positive |
| Level of split | Subepidermal | Intraepidermal (suprabasal acantholysis) |
| Target antigens | BP180 and BP230 (hemidesmosome) | Desmoglein 3, with or without desmoglein 1 |
| Direct immunofluorescence | Linear IgG and C3 along the basement membrane | Intercellular IgG and C3 ("chicken-wire" pattern) |
| Treatment | Potent topical corticosteroids (clobetasol), doxycycline, systemic steroids or steroid-sparing agents; dupilumab is FDA-approved for adults | Rituximab plus systemic corticosteroids for moderate to severe disease |
Biopsy technique: Take one biopsy from the edge of a fresh blister for routine histology and a second from perilesional intact skin in Michel's medium or saline for direct immunofluorescence. Serum antibody tests (such as BP180 and desmoglein ELISA) support the diagnosis.
Wound care: Leave small intact blisters in place, drain large tense blisters while keeping the roof as a biologic dressing, use nonadherent silicone or petrolatum dressings, avoid adhesives, and watch for infection in patients on immunosuppression.
Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis
- Definition by detached body surface area: SJS less than 10%, SJS/TEN overlap 10% to 30%, TEN more than 30%.
- Presentation: Fever and flu-like prodrome, painful dusky macules and atypical target lesions, epidermal sloughing, and mucosal involvement (eyes, mouth, genitals), usually 4 days to 4 weeks after starting a drug.
- Common culprits: Allopurinol, carbamazepine, lamotrigine, phenytoin, sulfonamide antibiotics, nevirapine, and oxicam NSAIDs. HLA-B*15:02 testing is recommended before carbamazepine in patients of certain Asian ancestries.
- SCORTEN (one point each): Age 40 or older, malignancy, heart rate 120 or more, detachment above 10% on day 1, BUN above 28 mg/dL, glucose above 252 mg/dL, and bicarbonate below 20 mEq/L; higher scores predict higher mortality.
- Care: Stop the culprit drug immediately, admit to a burn or intensive care unit, provide fluids, nutrition, pain control, eye care, and nonadherent dressings, avoid sulfonamide-containing products such as silver sulfadiazine, and monitor for sepsis.
Moisture-Associated Skin Damage (MASD)
MASD includes four forms: incontinence-associated dermatitis (IAD), intertriginous dermatitis (ITD), periwound moisture-associated dermatitis, and peristomal moisture-associated dermatitis.
| Feature | Incontinence-Associated Dermatitis | Pressure Injury |
|---|---|---|
| Cause | Urine or stool on skin | Pressure or shear over bone or under a device |
| Location | Perineum, buttocks, groin, skin folds; may extend down thighs | Over bony prominences (sacrum, coccyx, heels) or device sites |
| Shape and edges | Diffuse, irregular, poorly defined, mirror-image "kissing" lesions | Usually a single, more defined shape |
| Depth | Partial thickness; no necrosis | Can involve necrosis, slough, or deep tissue |
| Management | Gentle pH-balanced cleanser, skin protectant, containment of incontinence, treat Candida | Pressure redistribution and staged wound care |
Intertrigo occurs where skin touches skin; treat by drying and separating folds with moisture-wicking textiles, and add antifungal therapy for candidiasis (bright red with satellite papules and pustules). Erythrasma, a bacterial intertrigo, glows coral red under a Wood's lamp.
Skin Tears
Skin tears are traumatic wounds from shear, friction, or blunt force that separate skin layers, most common on the arms and legs of older adults.
| ISTAP Type | Description |
|---|---|
| Type 1 | No skin loss: a linear or flap tear in which the flap can cover the wound bed |
| Type 2 | Partial flap loss: the flap cannot cover the whole wound bed |
| Type 3 | Total flap loss: the entire wound bed is exposed |
Management: Control bleeding, gently cleanse, realign a viable flap with a moistened cotton-tipped applicator or gloved finger, apply a nonadherent silicone contact layer or foam, avoid adhesive strips on fragile skin, and draw an arrow on the dressing showing the direction of removal so the flap is not lifted. Prevent recurrence with moisturizers, padded rails, long sleeves, and careful handling.
Other Inflammatory Skin Conditions
- Hidradenitis suppurativa: Painful nodules, abscesses, and sinus tracts in the axillae, groin, and buttocks. Hurley stage I has abscesses without tracts or scarring, stage II has recurrent abscesses with tracts and scarring separated by normal skin, and stage III has diffuse interconnected tracts. Treatments include antibiotics, adalimumab, secukinumab, and bimekizumab (all FDA-approved), and surgical deroofing or wide excision.
- Psoriasis: New plaques can form at sites of trauma (the Koebner phenomenon), including surgical wounds and debridement sites.
- Stasis dermatitis: Itchy, scaly eczema of the lower legs from venous hypertension, often misdiagnosed as bilateral cellulitis; treat with compression, emollients, and short courses of topical steroids.
- Tools: Potassium hydroxide (KOH) preparation for fungi, Wood's lamp examination, patch testing, and biopsy with direct immunofluorescence.
Clinical Traps
Trap 1: Staging Incontinence Dermatitis as a Pressure Injury
Diffuse, shiny, irregular erosions in the gluteal cleft and perineum of an incontinent patient are IAD. Misclassifying them inflates pressure injury rates and leads to the wrong treatment.
Trap 2: Taking the DIF Biopsy From the Blister Center
Direct immunofluorescence needs perilesional skin. A sample from an eroded blister base may be falsely negative.
An 81-year-old man who started sitagliptin 8 months ago has intensely itchy, tense blisters on the thighs, flexures, and abdomen. There are no oral erosions, and the Nikolsky sign is negative. Which diagnostic approach and first-line treatment are most appropriate?
An 86-year-old woman with fecal and urinary incontinence has shiny, red, weeping, partial-thickness erosions with irregular, poorly defined edges in the gluteal cleft and across both inner buttocks in a mirror-image pattern. There is no necrosis, and the lesions are not centered over the sacrum or coccyx. How should this be classified and managed?
A 90-year-old woman on long-term prednisone bumps her forearm on a wheelchair and has a 5-cm skin tear. After gentle cleansing, the pale flap covers only about half of the wound bed. What is the ISTAP type, and what is appropriate care?