Introduction
The dermatology history OSCE may be a standalone skin history station or combined with a clinical photograph or lesion description task. You must elicit a systematic history of the skin complaint using a structured framework, identify red flags, and cover relevant triggers and associations.
💎 Clinical Pearl
Ask the patient to describe the rash or lesion in their own words first. "Can you tell me about this skin problem? When did you first notice it?" Then use a systematic framework to characterise it fully.
SCAM Framework for Skin Complaints
🧠 Mnemonic
SCAM — Site, Character, Associated features, Modifying factors
- Site: where on the body? Distribution pattern?
- Character: what does it look like? Colour, size, flat or raised, blistered, scaly?
- Associated features: itching, pain, burning, systemic symptoms (fever, joint pain, weight loss)
- Modifying factors: what makes it better or worse? Treatment tried?
Systematic Skin History
1. Onset and Course
- When did it start? Was onset sudden or gradual?
- Has it spread? Changed in appearance?
- Episodic or persistent?
- First episode or recurrent?
2. Distribution
Distribution pattern is diagnostically powerful:
| Distribution | Suggests |
|---|---|
| Flexural surfaces (antecubital fossa, popliteal fossa) | Atopic eczema |
| Extensor surfaces (elbows, knees) | Psoriasis |
| Sun-exposed areas (face, V of neck, dorsa of hands) | Photosensitive disorders (SLE, polymorphic light eruption) |
| Dermatomal (unilateral, single stripe) | Herpes zoster (shingles) |
| Symmetrical (both cheeks) | Rosacea, SLE malar rash |
| Palms and soles | Palmoplantar psoriasis, secondary syphilis, hand-foot-mouth disease |
3. Lesion Character
Use morphological terms:
- Macule (flat, coloured) vs papule (raised, under 1 cm) vs plaque (raised, over 1 cm) vs nodule (deep, over 1 cm)
- Vesicle (small fluid-filled blister) vs bulla (large blister) vs pustule (pus-filled)
- Scales, crusting, lichenification (thickened, leathery skin from chronic rubbing)
- Excoriations (scratch marks — indicates chronic pruritus)
4. Symptoms
- Pruritus (itching): worst at night = scabies, eczema; relieved by cooling = eczema; no itch = psoriasis usually
- Pain or burning: herpes zoster, cellulitis
- Systemic features: fever, arthralgia, fatigue (psoriatic arthritis, reactive arthritis, SLE)
5. Triggers and Aggravating Factors
- Contact triggers: detergents, soaps, metals (nickel), latex, plants (contact dermatitis)
- Food triggers: urticaria, atopic eczema in children
- Stress: psoriasis, eczema, rosacea
- Sun exposure: photosensitive disorders
- Medications: drug-induced rash — ask about recent new drugs
Key Differentials: Psoriasis vs Eczema
| Feature | Psoriasis | Atopic Eczema |
|---|---|---|
| Distribution | Extensor surfaces (elbows, knees, scalp, nails, lower back) | Flexor surfaces (antecubital fossa, popliteal fossa, neck) |
| Character | Well-demarcated erythematous plaques with silvery scale | Poorly demarcated erythema, vesicles, weeping, lichenification |
| Itch | Less prominent (may be absent) | Intense, worse at night |
| Associated conditions | Psoriatic arthritis, nail changes (pitting, onycholysis, subungual hyperkeratosis) | Atopy: asthma, allergic rhinitis, food allergy |
| Family history | Psoriasis in first-degree relative | Atopic triad in family |
| Triggers | Stress, infection (strep — guttate psoriasis), medications (beta-blockers, lithium, antimalarials), trauma (Koebner phenomenon) | Allergens, irritants, stress, heat, infection |
Skin Cancer Red Flags — ABCDE for Melanoma
🧠 Mnemonic
ABCDE Melanoma Red Flags:
Asymmetry — one half does not mirror the other
Border — irregular, ragged, or blurred edges
Colour — variation in colour within the lesion
Diameter — greater than 6 mm (size of a pencil eraser)
Evolution — any change in size, shape, colour, or any new symptom (bleeding, itching, crusting)
Other Skin Cancer Red Flags
- Non-healing ulcer or wound (squamous cell carcinoma, basal cell carcinoma)
- Pearly, rolled border with central ulceration: BCC
- Firm, flesh-coloured or erythematous nodule that bleeds easily: SCC
- Previous skin cancer, immunosuppression, extensive UV exposure, Fitzpatrick skin type I or II
Drug History
Always ask about: recent new medications (drug-induced rash — almost any drug can cause a morbilliform rash); antibiotics (amoxicillin maculopapular rash); allopurinol, carbamazepine, lamotrigine (Stevens-Johnson syndrome risk); OCP and minocycline (SLE-like rash).
Social and Family History
- Occupation: hand dermatitis in healthcare workers (latex, frequent washing), chefs, hairdressers
- Pets: tinea (ringworm from cats and dogs), scabies
- Contact with others with similar rash (scabies, impetigo)
- Family history of atopy, psoriasis, skin cancer
"How do you differentiate psoriasis from eczema in the history?"
Psoriasis affects extensor surfaces (elbows and knees), presents with well-demarcated plaques with silvery scale, is often less itchy than eczema, and is associated with nail changes and psoriatic arthritis. Eczema affects flexural surfaces (antecubital and popliteal fossae), is intensely itchy especially at night, presents with poorly defined weeping or lichenified skin, and is associated with personal or family history of atopy.
"What are the ABCDE red flags for melanoma?"
Asymmetry (one half does not mirror the other), Border (irregular, ragged, or notched edge), Colour (uneven pigmentation with multiple shades), Diameter (greater than 6 mm), and Evolution (any change in size, shape, colour, or any new symptom such as bleeding or itching). Any lesion with these features requires urgent referral under the 2-week wait rule.
"What drug history questions are important in a dermatology OSCE?"
Ask about all medications including OTC preparations and herbal remedies. Any drug can cause a maculopapular drug rash (most commonly antibiotics, particularly amoxicillin). Allopurinol, carbamazepine, and lamotrigine carry a risk of Stevens-Johnson syndrome. Beta-blockers, lithium, and antimalarials can trigger or worsen psoriasis. NSAIDs can exacerbate urticaria.
"What distribution patterns are diagnostically important in skin disease?"
Flexural distribution (antecubital and popliteal fossae) suggests atopic eczema. Extensor distribution (elbows, knees) with silvery scale suggests psoriasis. Dermatomal unilateral distribution suggests herpes zoster. Sun-exposed distribution suggests photosensitive disorders or drug photosensitivity. Palms and soles involvement suggests palmoplantar psoriasis, secondary syphilis, or hand-foot-mouth disease.
Related guides: Skin Lesion Examination OSCE | Musculoskeletal History OSCE | How to Take a Cardiology History OSCE