Seborrheic dermatitis

Seborrheic dermatitis is a common chronic inflammatory skin condition that affects areas with high sebaceous activity (e.g., scalp). The etiology remains unknown, but microbial colonization of the skin (esp. Malassezia), immunological factors, climate, or stress have been implicated. This condition is characterized by intermittent flares with intervening asymptomatic periods. Patients may exhibit either an erythematous, patchy scaling, or greasy yellow crusts, both of which could be associated with burning or itching. Early treatment of acute flares with topical glucocorticosteroids is recommended. Topical ketoconazole is used to relieve symptoms. The condition tends to recur over a lifetime despite treatment. Infantile seborrheic dermatitis (also referred to as “cradle cap”) is a subtype of seborrheic dermatitis and appears shortly after birth, primarily affecting the scalp. As opposed to seborrheic dermatitis in adults, it usually heals without treatment after a few months.

• Sex: ♂ > ♀
• Bimodal distribution: infants 2 weeks to 12 months; puberty and early adulthood.
• Prevalence: approximately 3–5% of general population worldwide

References:^{[1][2][3][4][5]}

Epidemiological data refers to the US, unless otherwise specified.

• Unknown etiology; may be associated with Malassezia species
• Predisposing factors
  • Parkinson disease
  • Immunodeficiency (e.g., HIV infection)
  • Oily skin (seborrhea)
  • Androgenetic alopecia
  • Familial history of seborrhoeic dermatitis, psoriasis

References:^[6][7][8]

• The pathophysiology is not yet fully understood
  • Colonization of the yeast Malassezia furfur (previously known as Pityrosporum ovale) in areas with sebaceous glands
  • → inadequate or abnormal immune response to the yeast ) and/or exposure to irritants (toxin production or lipase activity) responses
  • → inflammatory reaction of the skin
• Endogenous precipitants; : psychological stress; , fatigue, sleep deprivation, and hormonal changes
• Exogenous precipitants; : climate (the condition improves in the summer months and worsens in winter; ), trauma (e.g., excoriation of the skin from scratching), medication

References:^{[4][5][9][10]}

• Chronic course with episodic, active phases (associated burning and itching) alternating with inactive, asymptomatic periods
• Ranges from erythematous plaques with patchy scaling → greasy yellow crusts, distributed along areas with hair and oily skin:
  • Scalp (dandruff and itching)
  • Forehead/hairline and retroauricular area
  • Nasolabial fold, eyebrows and periocular region (blepharitis: scaly red eyelid margins)
  • Cheeks and chin
  • Presternal and interscapular regions
  • Axillae, under breasts, umbilicus, and groin area

References:^[4][5][11]

• Primarily a clinical diagnosis

Consider HIV or Parkinson's disease if there is a marked or unusual distribution of seborrheic dermatitis!References:^[5]

• See “Differential diagnosis of scaling” in psoriasis
• Atopic dermatitis: Lesions are usually dry in atopic dermatitis, rather than greasy as in seborrheic dermatitis.
• Contact dermatitis: The rash distribution reflects the areas and shapes of external exposure.

The differential diagnoses listed here are not exhaustive.

• Lifestyle modifications
  • Exposure to sunlight may help relieve symptoms.
  • Avoid precipitating factors if possible
• Medical therapy
  • Creams or shampoos ; containing selenium sulfide, zinc pyrithione, salicylic acid, tar, or sulfur
  • Topical antifungals: ketoconazole (first-line drug), naftifine
  • Topical corticosteroids for severe acute flares
  • Systemic ketoconazole or fluconazole for severe or refractory cases

Steroidal creams should only be used for short periods because long-term use increases the risk of recurrences.

References:^[5][7][12]

• Exacerbation of seborrheic dermatitis may lead to generalized erythroderma
• Secondary bacterial infection

References:^[4]

We list the most important complications. The selection is not exhaustive.

• No cure: often a chronic, recurrent course
• The active phases of seborrheic dermatitis are easily controllable with treatment

References:^[5]

Infantile seborrheic dermatitis

• Onset: occurs shortly after birth
• Clinical features
  • Erythematous (or salmon-colored) scaling plaques → greasy, yellow, adherent scales
  • Location: scalp (common; also known as cradle cap), forehead, nose, external ear, umbilical area, or intertriginous areas
  • Pruritus (rarely)
• Usually a clinical diagnosis
• Differential diagnosis
  • Atopic dermatitis; : While seborrheic dermatitis typically presents during the first 3 months of life; , atopic dermatitis tends to appear at a later stage.
  • Diaper dermatitis; : usually spares intertriginous areas (skin folds)
• Treatment
  • Usually resolves spontaneously without medical therapy
  • Regular bathing, use of baby shampoos, and application of an emulsifying ointment may help relieve symptoms.
  • Topical corticosteroids (low potency) and ketoconazole in severe cases
• Complications (rare)
  • Erythroderma
  • Leiner disease: most severe form of infantile seborrheic dermatitis presenting with erythroderma, recurrent diarrhea, and failure to thrive

References:^{[13][14][15][16]}