12.7 Vascular Dermatoses, Environmental Injury & Cutaneous Signs of Systemic Disease
Key Takeaways
- Vascular dermatoses, dermatologic immunology, cutaneous manifestations of nutritional deficiencies, environmental injury of skin and pressure injuries are enumerated blueprint subsections.
- Erythema nodosum is a septal panniculitis whose leading causes are streptococcal infection, sarcoidosis, inflammatory bowel disease, drugs and tuberculosis.
- Palpable purpura indicates leukocytoclastic vasculitis and requires evaluation for systemic involvement, particularly renal.
- Pellagra from niacin deficiency causes a photodistributed dermatitis with diarrhea and dementia.
- Frostbite is rewarmed rapidly in warm water and definitive tissue demarcation is deferred for weeks.
1. Erythema Nodosum
A septal panniculitis presenting as tender, warm, erythematous subcutaneous nodules on the anterior shins, typically bilateral. The lesions do not ulcerate and heal without scarring, evolving through bruise-like color changes.
Causes — the differential is the exam content:
| Category | Causes |
|---|---|
| Infection | Streptococcal pharyngitis (the most common identified cause), tuberculosis, coccidioidomycosis, histoplasmosis, Yersinia |
| Inflammatory | Sarcoidosis (Lofgren syndrome), inflammatory bowel disease, Behcet disease |
| Drugs | Oral contraceptives, sulfonamides, penicillins |
| Other | Pregnancy, lymphoma, idiopathic in a large fraction |
Lofgren syndrome — erythema nodosum, bilateral hilar lymphadenopathy, fever and polyarthritis — is an acute sarcoidosis presentation with an excellent prognosis that frequently resolves without corticosteroids.
Evaluation of a first episode: history and examination, throat culture or antistreptolysin O, chest radiograph (for hilar adenopathy or tuberculosis), tuberculin or interferon-gamma testing, and a pregnancy test. Treatment is of the underlying cause plus NSAIDs, rest and leg elevation.
2. Leukocytoclastic Vasculitis and Palpable Purpura
Palpable purpura is the cutaneous signature of small-vessel vasculitis — it is palpable because inflammation and extravasation raise the lesion above the skin, distinguishing it from the flat purpura of thrombocytopenia.
Causes:
- Drugs — the most common cause: beta-lactams, sulfonamides, NSAIDs, allopurinol, thiazides
- Infection — streptococcal, hepatitis B and C, endocarditis
- IgA vasculitis (Henoch-Schonlein purpura) — purpura on the lower extremities and buttocks, arthralgia, abdominal pain and IgA nephropathy; more severe in adults
- Cryoglobulinemia — strongly associated with hepatitis C
- ANCA-associated vasculitis, connective tissue disease, malignancy
The essential step is determining whether the vasculitis is skin-limited or systemic. Obtain a urinalysis looking for hematuria, red cell casts and proteinuria, plus creatinine, complete blood count, liver enzymes, hepatitis serologies, complement levels, ANCA, cryoglobulins and antinuclear antibody. Skin-limited disease resolving with drug withdrawal is common; renal involvement changes management entirely.
3. Erythema Multiforme
Targetoid lesions with three concentric zones, favoring the acral surfaces — palms, soles, extensor extremities — and spreading centrally.
Erythema multiforme is usually infectious, most often herpes simplex virus (recurrent erythema multiforme is nearly always HSV-driven and is prevented with suppressive antiviral therapy), and Mycoplasma pneumoniae in younger patients. This is a key contrast: Stevens-Johnson syndrome and toxic epidermal necrolysis are usually drug-induced, present with atypical targets and dusky macules on the trunk, involve mucosa extensively, and carry substantial mortality.
4. Leg Ulcers
An enumerated topic under vascular dermatoses, and a common source of misdiagnosis.
| Venous | Arterial | Neuropathic | |
|---|---|---|---|
| Location | Medial malleolus (gaiter area) | Distal toes, pressure points, lateral malleolus | Plantar pressure points |
| Appearance | Irregular, shallow, exudative | Punched-out, dry, pale or necrotic base | Punched-out with surrounding callus |
| Pain | Aching, better with elevation | Severe, worse with elevation, better dependent | Painless |
| Surrounding skin | Hemosiderin staining, lipodermatosclerosis, varicosities | Shiny, hairless, cool, absent pulses | Callus, deformity |
| Key test | Duplex ultrasound | Ankle-brachial index | Monofilament testing |
| Treatment | Compression | Revascularization | Offloading |
Compression is the treatment for venous ulcers and is contraindicated in significant arterial disease — so an ankle-brachial index should be measured before applying compression. Applying compression to an ischemic limb causes tissue necrosis, which is exactly the trap exam items are built around.
Pyoderma gangrenosum should be considered for an ulcer with a violaceous undermined border that enlarges rapidly and is exquisitely painful, often with pathergy (worsening after debridement). It is associated with inflammatory bowel disease, inflammatory arthritis and hematologic malignancy. Surgical debridement worsens it — the treatment is immunosuppression, and recognizing this prevents serious harm.
5. Cutaneous Manifestations of Nutritional Deficiency
A named blueprint subsection.
| Deficiency | Skin findings | Other features |
|---|---|---|
| Niacin (B3) — pellagra | Photodistributed dermatitis, Casal necklace | Diarrhea, dementia, death; seen in alcohol use, carcinoid, isoniazid |
| Vitamin C — scurvy | Perifollicular hemorrhage, corkscrew hairs, gingival bleeding | Poor wound healing, arthralgia |
| Zinc | Acrodermatitis enteropathica — periorificial and acral erosive dermatitis | Alopecia, diarrhea, impaired taste; after bariatric surgery, in parenteral nutrition |
| Vitamin A | Follicular hyperkeratosis (phrynoderma) | Night blindness, xerophthalmia |
| Essential fatty acids | Dry scaly dermatitis | Prolonged fat-free parenteral nutrition |
| Vitamin K | Purpura, easy bruising | Elevated prothrombin time |
| Iron | Koilonychia, angular cheilitis, glossitis | Microcytic anemia |
| B12 / folate | Hyperpigmentation, glossitis | Macrocytic anemia; B12 also myeloneuropathy |
Think of these after bariatric surgery, in chronic alcohol use, in malabsorption, in restrictive eating disorders, and in prolonged parenteral nutrition — the same populations in which the exam places them.
6. Environmental Injury and Pressure Injuries
Frostbite — freezing injury with initial numbness and waxy pallor. Rewarm rapidly in circulating water at 37 to 39 degrees Celsius, and do not rewarm if there is any risk of refreezing, since freeze-thaw-refreeze cycles are far more damaging. Rewarming is painful and requires analgesia. Do not debride early: the extent of tissue loss cannot be judged for weeks, and premature amputation removes salvageable tissue. Clear blisters may be drained; hemorrhagic blisters indicate deeper injury and are left intact.
Burns — assess depth and total body surface area involved. Superficial partial-thickness burns are painful and blanch; full-thickness burns are insensate, leathery and do not blanch. Circumferential full-thickness burns risk compartment syndrome and require escharotomy. Fluid resuscitation is calculated from body surface area involved, and inhalation injury should be suspected with facial burns, singed nasal hairs, carbonaceous sputum or hoarseness.
Pressure injuries — an enumerated subsection under both Dermatology and Geriatric Syndromes, covered in detail with geriatric syndromes. The essential dermatologic point is staging by the deepest tissue visible, and that a stage cannot be assigned when the wound base is obscured by slough or eschar (unstageable), while deep tissue pressure injury appears as a persistent non-blanchable deep red, maroon or purple discoloration of intact skin.
A 68-year-old man with diabetes and a 50 pack-year smoking history has a shallow exudative ulcer over the medial malleolus with surrounding hemosiderin staining and varicosities. A clinician proposes multilayer compression bandaging. Which step is most important before applying compression?
A 58-year-old woman with a history of alcohol use disorder presents with a symmetric scaly erythematous eruption on the dorsal hands, face and a broad band across the anterior neck, along with chronic diarrhea and new confusion. Which deficiency best explains this constellation?