Dermatology MCQ - Inflammatory Dermatoses - Seborrhoeic Dermatitis

A 25-year-old man presents with a several-month history of a red, greasy, scaly rash affecting his scalp, nasolabial folds, and the retroauricular areas. The scaling on the scalp is diffuse and yellow in color. He reports mild pruritus. The rash improves with sun exposure and worsens during periods of stress. Which of the following is the most likely diagnosis?

A. Psoriasis
B. Systemic Lupus Erythematosus
C. Allergic Contact Dermatitis
D. Seborrhoeic Dermatitis
E. Tinea Faciei

Correct Answer: D. Seborrhoeic Dermatitis

Explanation:

• The presentation is classic for Seborrhoeic Dermatitis. The key diagnostic clues are the distribution in seborrhoeic areas (scalp, face [nasolabial folds, eyebrows, glabella], and retroauricular folds), the characteristic greasy, yellowish scale, and the chronic, relapsing course. The history of improvement with sun exposure and exacerbation with stress is also commonly reported.

• Why the other options are incorrect:

  • A. Psoriasis: Scalp psoriasis presents with well-demarcated, thick, silvery-white scales, not a diffuse, greasy, yellow scale. Psoriasis on the face is less common and would typically be more plaque-like. It does not preferentially affect the nasolabial folds.

  • B. Systemic Lupus Erythematosus: A malar rash from lupus is typically a fixed, erythematous, flat or raised plaque across the cheeks and nose, sparing the nasolabial folds. It does not present with greasy scaling in the scalp and retroauricular areas.

  • C. Allergic Contact Dermatitis: This would present with more acute, intensely pruritic, and often vesicular inflammation. The distribution would correspond to contact with an allergen (e.g., from haircare products, cosmetics), not the symmetric, classic seborrhoeic distribution.

  • E. Tinea Faciei: This fungal infection on the face often presents as an annular, expanding plaque with a raised, scaly, and sometimes vesicular border with central clearing. A KOH preparation would be positive for hyphae. The diffuse, bilateral, and non-annular pattern in seborrhoeic areas is not typical for tinea.

Key Points for Exams

• Pathophysiology: Associated with an inflammatory reaction to the yeast Malassezia spp. (formerly Pityrosporum ovale) in genetically predisposed individuals.

• Associations: It is extremely common in the general population. Severe or refractory seborrhoeic dermatitis can be a cutaneous marker of HIV infection and is also associated with Parkinson's disease.

• Infantile Form: A self-limiting form known as "cradle cap" occurs in infants.

• Prognosis: The condition is chronic and relapsing. It is not curable, but it can be well-controlled with consistent therapy.

• Management:

  1. Topical Antifungals: First-line treatment to reduce Malassezia colonization. Includes ketoconazole or ciclopirox shampoos, creams, and lotions.

  2. Low-Potency Topical Corticosteroids: Used for short courses to rapidly reduce inflammation and pruritus (e.g., hydrocortisone 1-2.5% cream).

  3. Topical Calcineurin Inhibitors: Pimecrolimus cream or tacrolimus ointment are excellent steroid-sparing alternatives, especially for facial and intertriginous areas.

  4. Keratolytics: For scalp involvement, shampoos containing salicylic acid, coal tar, or selenium sulfide can help lift scale.