Seborrheic Dermatitis | Atlas Dermato

General information

Chronic, relapsing erythematous and scaly inflammatory dermatosis predominantly affecting areas rich in sebaceous glands.
Associated with an abnormal inflammatory response to Malassezia yeasts, which are normal components of the skin microbiome.
Characterized by a chronic course with flares and remissions.
Mainly occurs in two forms: infantile seborrheic dermatitis and adolescent/adult seborrheic dermatitis.
Infantile disease usually develops during the first few months of life and often resolves spontaneously.
Adult disease generally begins after puberty and is particularly common between 30 and 60 years of age.
More common in men.
Flares are often more frequent or severe during fall and winter.
May be particularly severe or refractory in patients with HIV infection or neurological disorders such as Parkinson disease.
Severe generalized seborrheic dermatitis in an infant associated with diarrhea, recurrent infections, or failure to thrive should prompt evaluation for an underlying systemic disorder or immunodeficiency.

Poorly demarcated erythematous scaly patches or plaques.
Greasy yellow or white scales, sometimes flaky.
Variable degree of erythema.
Variable pruritus.
Scalp involvement may present with diffuse dandruff ± scaly plaques.
In skin folds, lesions may appear more erythematous and less scaly because of moisture.
In darker skin tones, erythema may be less apparent and pigmentary changes may be more prominent.

Scalp +++.
Hairline and forehead.
Eyebrows and glabella.
Nasolabial folds.
Retroauricular region and external auditory canal.
Beard and moustache areas.
Presternal region and upper trunk.
Skin folds in more extensive disease.
In infants: scalp, face, retroauricular areas, and skin folds, sometimes including the diaper area.

Yellowish or white scales.
Variable erythematous background.
Fine arborizing or branching vessels may be present.
Vascular structures tend to have an irregular distribution.
Dermoscopy may help distinguish seborrheic dermatitis from psoriasis, which more typically shows white scales and regularly distributed dotted vessels.

Primarily a clinical diagnosis based on characteristic morphology and distribution.
Laboratory investigations are usually unnecessary.
KOH preparation ± fungal culture if dermatophytosis is suspected.
Bacterial culture if secondary bacterial infection is suspected.
Skin biopsy is rarely required and is generally reserved for atypical or refractory disease.

Main goals: reduce Malassezia, control inflammation, and prevent recurrence.
Scalp flare: ketoconazole 2% shampoo 2–3×/week for 2–4 weeks, leaving it on for approximately 3–5 minutes before rinsing.
Alternative: ciclopirox shampoo, according to the available formulation.
Significant scalp inflammation: briefly add an appropriate topical corticosteroid formulation such as a solution, foam, or oil.
Face/trunk flare: ketoconazole 2% cream once or twice daily for 2–4 weeks.
Significant facial inflammation: hydrocortisone 1–2.5% once or twice daily for only a few days, minimizing corticosteroid exposure on facial skin.
Tacrolimus or pimecrolimus may be used as steroid-sparing alternatives, particularly for facial disease or frequent recurrences.
Scalp maintenance: antifungal shampoo approximately once weekly, adjusted according to recurrence frequency.
Facial maintenance: intermittent topical antifungal therapy; a topical calcineurin inhibitor may be considered for frequent recurrences.
Avoid prolonged use of potent topical corticosteroids, particularly on the face and skin folds.
Severe or refractory disease should be managed individually by a dermatologist; systemic antifungal therapy may occasionally be considered.