Seborrheic Dermatitis

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Seb Derm 101 - The Greasy Itch

  • Chronic, relapsing inflammatory dermatitis presenting with greasy yellow scales and underlying erythema.
  • Common sites: scalp (dandruff), face (nasolabial folds, eyebrows, glabella, retroauricular), chest, intertriginous areas.
  • Infants ("cradle cap") & adults (peak 30-60 yrs, M > F). Seborrheic dermatitis on face across different skin tones

⭐ Seborrheic dermatitis has a biphasic age distribution, peaking in infancy (first 3 months) and again in puberty/adulthood (30-60 years).

Etiopathogenesis - Yeast's Party Foul

  • Key Culprit: Malassezia species (e.g., M. globosa, M. restricta), a lipophilic commensal yeast.
  • Pathophysiology:
    • Malassezia metabolizes sebum triglycerides.
    • Produces irritating free fatty acids (e.g., oleic acid).
    • Disrupts skin barrier integrity.
    • Induces inflammation & keratinocyte hyperproliferation.
  • Contributing Factors:
    • Genetic predisposition.
    • Sebum quantity & composition.
    • Immune system status (critical in HIV).
    • Neurological conditions (e.g., Parkinson's disease).
    • Environmental factors (stress, humidity). Seborrheic Dermatitis Pathogenesis Diagram

⭐ Association with HIV/AIDS is strong; severe or refractory seborrheic dermatitis can be an early cutaneous marker of HIV infection, often seen with CD4 counts < 400 cells/µL.

Clinical Features - Flakes & Red Faces

  • Primary Lesions: Erythematous patches with overlying greasy, yellowish scales ("flakes").
  • Scalp Involvement:
    • Mild: Diffuse scaling (dandruff).
    • Severe: Inflamed, thick, adherent, yellowish crusts; potential hair loss.
  • Facial Involvement ("Red Faces"): Eyebrows, glabella, nasolabial folds, retroauricular. Blepharitis common.
  • Other Affected Areas:
    • Presternal chest: "Petaloid" or annular configuration.
    • Intertriginous zones (axillae, groin, inframammary): Erythema, moist scaling.
  • Symptoms: Pruritus (variable, often mild), burning sensation.

⭐ In infants, seborrheic dermatitis often presents as “cradle cap” (adherent, greasy scales on the scalp) but can also affect the face, diaper area, and intertriginous zones.

Diagnosis & DDx - Spotting the Impostors

  • Clinical diagnosis usually sufficient.
  • Biopsy (rare): Parakeratosis, acanthosis, spongiosis.
  • Key DDx:
    ConditionKey Differentiators
    PsoriasisDry, silvery, thick scales; extensor; nail pitting
    Atopic DermatitisIntense pruritus; flexural; atopic history
    Tinea CapitisAlopecia, broken hairs; +KOH/culture
    RosaceaRedness, telangiectasia, papules/pustules; no scales
    Discoid LupusAdherent scale, follicular plugging, atrophy, scarring

⭐ A key differentiator from psoriasis is that seborrheic dermatitis scales are typically greasy and yellowish, while psoriasis scales are dry, silvery, and thicker.

Treatment Toolkit - Taming the Flare-ups

  • Goals:Malassezia, ↓ Inflammation, Remove scales.
  • First-line Therapy:
    • Topical Antifungals (Ketoconazole, ciclopirox, selenium sulfide, Zn pyrithione).
    • Topical Corticosteroids (Low-potency, short-term; e.g., hydrocortisone).
  • Scalp Specifics:
    • Medicated Shampoos (Ketoconazole 2%, SeS 2.5%).
    • Severe: Add topical steroid solution.
  • Face/Body Specifics:
    • Antifungal Creams (Ketoconazole 2%, ciclopirox 1%).
    • Severe: Add low-potency steroid cream (hydrocortisone 1%).
  • Adjuncts:
    • Keratolytics (Salicylic acid) for thick scales.
  • Maintenance:
    • Reduced frequency; TCIs (Pimecrolimus, Tacrolimus) for face.
  • Refractory Cases:
    • Oral antifungals, Isotretinoin, Phototherapy.

Topical ketoconazole 2% shampoo or cream is a cornerstone of treatment due to its antifungal activity against Malassezia species and its anti-inflammatory effects.

High-Yield Points - ⚡ Biggest Takeaways

  • Common sites include the scalp (dandruff), face (nasolabial folds, eyebrows, glabella), chest, and flexures.
  • Strongly associated with the yeast Malassezia furfur (Pityrosporum ovale).
  • Infantile form is known as cradle cap; adult form is chronic and relapsing.
  • Presents with greasy, yellowish scales on an erythematous base.
  • Exacerbated by stress, cold/dry weather, immunosuppression (e.g., HIV), and Parkinson's disease.
  • Severe or widespread seborrheic dermatitis can be a marker for HIV infection.
  • Management includes topical antifungals (e.g., ketoconazole), mild topical corticosteroids, and keratolytics for scales.
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Practice Questions: Seborrheic Dermatitis

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Flashcards: Seborrheic Dermatitis

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_____ is the only recommended systemic therapy for chronic hand eczema.

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_____ is the only recommended systemic therapy for chronic hand eczema.

Alitretinoin

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