What is the diagnosis and management of a patient presenting with erythematous patches and a rough, scaly erythematous base on the scalp, face, and arms?

Diagnosis: Seborrheic Dermatitis

The most likely diagnosis is seborrheic dermatitis, characterized by erythematous patches with greasy, yellowish scales affecting sebaceous-rich areas including the scalp, face, and upper trunk. 1

Clinical Features Supporting This Diagnosis

The presentation of erythematous patches with rough, scaly erythematous base on the scalp, face, and arms is highly consistent with seborrheic dermatitis, which:

• Affects areas with high sebaceous gland density, particularly the scalp, face (especially nasolabial folds, eyebrows, and forehead), and upper trunk 2
• Presents with greasy yellowish scaling, erythema, and secondary inflammation from Malassezia yeast 2
• Commonly involves the scalp with thick plaques covered by scales 3

Key Differential Diagnoses to Exclude

Psoriasis should be considered but is less likely given the distribution pattern. Look for well-demarcated, indurated plaques with thick silvery scale rather than greasy yellow scales, and inquire about personal or family history of psoriasis 1

Atopic dermatitis presents with more intense pruritus and lichenification in chronic cases, often with flexural involvement rather than sebaceous areas 1, 4

Contact dermatitis would show sharp demarcation corresponding to contact areas and requires patch testing if suspected 5

Management Approach

First-Line Topical Treatment

Initiate combination therapy with topical antifungal medication plus short-term low-potency corticosteroid:

Antifungal Therapy (Primary Treatment)

• Ketoconazole 2% cream applied to affected facial and body areas twice daily 1
• For scalp involvement: Use ketoconazole 2% shampoo, selenium sulfide 1% shampoo, or betadine shampoo 2-3 times weekly 1
• Solutions, foams, or shampoos are preferred over ointments for scalp treatment due to ease of application through hair 1

Anti-inflammatory Therapy (Short-term Only)

• Hydrocortisone 1% or prednicarbate 0.02% cream for significant erythema and inflammation 1
• Critical limitation: Use for no more than 2-4 weeks, especially on the face, due to risk of skin atrophy, telangiectasia, and tachyphylaxis 1, 6
• Avoid higher-potency corticosteroids like clobetasol on the face due to high risk of adverse effects 1

Essential Supportive Skin Care

Implement these measures concurrently with topical medications:

• Use mild, pH-neutral (pH 5) non-soap cleansers or dispersible creams as soap substitutes 1
• Apply fragrance-free moisturizers containing petrolatum or mineral oil immediately after bathing to damp skin 1
• Avoid all alcohol-containing preparations on the face as they significantly worsen dryness and trigger flares 1
• Use tepid (not hot) water for bathing 1
• Pat skin dry rather than rubbing 1

Treatment Duration and Tapering Strategy

After initial 2-4 week treatment course:

• Gradually taper corticosteroid frequency (e.g., twice daily → once daily → every other day → discontinue) 1
• Continue antifungal therapy as maintenance, as seborrheic dermatitis is chronic and relapsing 2
• Consider switching to ketoconazole shampoo for long-term scalp maintenance 1

Monitoring for Complications

Watch for secondary infections requiring specific treatment:

• Bacterial superinfection (Staphylococcus aureus): Look for crusting, weeping, or increased warmth; treat with oral flucloxacillin 1
• Herpes simplex superinfection: Suspect if grouped vesicles or punched-out erosions appear; initiate oral acyclovir immediately 1

When to Refer to Dermatology

Refer if any of the following occur 1:

• Diagnostic uncertainty or atypical presentation
• Failure to respond after 4 weeks of appropriate first-line therapy
• Recurrent severe flares despite optimal maintenance therapy
• Need for second-line treatments (phototherapy, systemic agents)

Second-Line Options for Refractory Cases

If inadequate response to first-line therapy 1:

• Narrowband UVB phototherapy has demonstrated efficacy in open studies for recalcitrant seborrheic dermatitis 1
• Avoid applying moisturizers immediately before phototherapy as they create a bolus effect 1

Common Pitfalls to Avoid

• Do not use non-sedating antihistamines as they provide no benefit in seborrheic dermatitis 1
• Avoid prolonged corticosteroid use beyond 2-4 weeks, particularly on the face 1, 6
• Do not use greasy or occlusive products that can promote folliculitis 1
• Avoid harsh soaps and detergents that remove natural skin lipids 1
• Do not overlook occupational or hobby-related exposures that could indicate contact dermatitis 5