Definition
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Seborrheic dermatitis (SD): chronic, relapsing, inflammatory skin condition affecting sebaceous-rich areas.
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Characterized by erythematous, greasy, yellowish scales.
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Often mildly pruritic, more common in infants and adults.
Epidemiology & Risk Factors
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Affects 2–5% of adults, more in men.
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Peaks: infants (“cradle cap”) and adults 30–60 years.
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Risk factors:
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Neurological disorders (Parkinson’s disease)
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HIV infection
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Stress, cold weather
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Oily skin or seborrhea
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Pathophysiology
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Malassezia yeast overgrowth on sebaceous skin → inflammatory response.
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Genetic and immune factors contribute.
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Sebum production promotes yeast proliferation.
Clinical Features
| Feature | Typical Location | Appearance |
|---|---|---|
| Infants | Scalp (“cradle cap”), face, diaper | Yellow, greasy scales, minimal erythema |
| Adults | Scalp, eyebrows, nasolabial folds, ears, chest | Erythematous, greasy, yellowish scales |
| Pruritus | Usually mild | Can be moderate in severe cases |
| Chronicity | Relapsing | Seasonal flares (winter) |
💡 Exam Tip: Face involvement often nasolabial folds; scalp involvement may be diffuse with greasy plaques.
Differential Diagnosis
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Atopic dermatitis – itchy, flexural involvement, history of atopy.
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Psoriasis – well-demarcated plaques with silvery scales, extensor surfaces.
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Tinea capitis – patchy hair loss, scaling, possible lymphadenopathy.
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Rosacea – central facial erythema, no scales.
Investigations
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Usually clinical diagnosis; investigations rarely required.
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Consider KOH prep if fungal infection suspected.
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HIV testing in severe, refractory adult SD.
Management
General Measures
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Gentle cleansing with non-soap cleansers.
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Avoid harsh detergents, frequent scratching.
Topical Therapy
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Mild-moderate: antifungal shampoos/creams (ketoconazole, ciclopirox)
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Inflammatory flares: low-potency topical corticosteroids (short-term)
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Adjunct: selenium sulfide, zinc pyrithione, coal tar shampoo
Chronic/Refractory
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Combination therapy: antifungal + mild steroid.
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Consider long-term maintenance therapy with antifungal shampoo.
Complications
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Secondary bacterial infection (rare).
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Cosmetic/psychosocial impact from visible lesions.
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Chronic, relapsing course.
PLAB-Style Questions
Q1: A 35-year-old man presents with erythematous, greasy, yellowish scales on his scalp and nasolabial folds. Mild pruritus is present. What is the most likely diagnosis?
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A. Psoriasis
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B. Atopic dermatitis
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C. Seborrheic dermatitis
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D. Tinea faciei
✅ Answer: C. Seborrheic dermatitis
(Greasy, yellowish scales in seborrheic distribution with mild pruritus.)
Q2: An adult patient with HIV presents with severe, widespread seborrheic dermatitis. Which of the following is the most appropriate initial management?
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A. Oral antifungal therapy
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B. Topical ketoconazole or antifungal shampoo
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C. Systemic corticosteroids
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D. Emollients only
✅ Answer: B. Topical ketoconazole or antifungal shampoo
(First-line therapy; systemic therapy rarely needed unless refractory.)
High-Yield Pearls
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Seborrheic dermatitis → sebaceous-rich areas: scalp, face, chest.
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Greasy, yellow scales differentiate from psoriasis (silvery, dry).
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Mild pruritus, chronic relapsing course.
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Antifungal shampoos are mainstay; short-term mild steroids for flares.
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Severe or refractory SD → consider HIV testing.
