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- An erythematous, scaly, greasy dermatitis that favors the sebaceous areas of the body, including the scalp, face, postauricular, central chest, and intertriginous areas
- The distribution pattern and clinical course varies with age. Infants commonly manifest predominantly self-limiting scalp involvement (“cradle cap”), while adults and adolescents more commonly demonstrate chronic involvement of the face, ears, and scalp.
Frequent washing with a medicated shampoo containing sulfur, selenium sulfide, salicylic acid, tar, corticosteroid, an antifungal agent, or zinc pyrithione or application of a medicated lotion, foam, gel or cream containing either one of the aforementioned compounds can reduce disease flares. There are no other preventive measures and modulation of dietary intake is of no benefit.
- There are 2 populations in whom seborrheic dermatitis develops: Infants, in which seborrheic dermatitis usually develops after the first 3–4 weeks of life, peaks at age 3 months, and usually resolves by 1 year of age; and adolescents and adults, in whom it usually persists, although the disease may be seen in children of all ages.
- In adults, seborrheic dermatitis is more common in males.
- The development of seborrheic dermatitis during infancy does not predict the development of adolescent and/or adult disease.
Although it is one of the more common skin diseases seen in infants as well as in adolescents and adults, the incidence of seborrheic dermatitis is unknown.
- Affects 2–5% of the adult population.
- Affects ∼6% of children 2 to 10 years of age.
- Affects ∼ 18% of infants <2 years of age.
Controversy exists as to whether there is a genetic predisposition. There is evidence that it is more common in families, but not spouses, of affected patients.
- Although not an infection per se, there is increasing acceptance that the lipophilic yeast Malassezia, a commensal skin organism, is a contributing factor. Increased sebaceous gland activity likely favors the growth of Malassezia. The use of topical antifungal agents such as ketoconazole significantly decreases the number of Malassezia yeast in seborrheic dermatitis patients with subsequent clinical improvement.
- The local host immune response to Malassezia toxins or enzymes also plays a probable role in the development of seborrheic dermatitis. Seborrheic dermatitis is one of the most common cutaneous manifestations of AIDS in adults, where it can be particularly severe and recalcitrant to standard therapy.
- Androgen-mediated stimulation of sebaceous gland activity is likely important, given that seborrheic dermatitis presents in infancy and puberty.
- The histopathologic findings are nonspecific and include parakeratosis, acanthosis, spongiosis, elongation of the rete ridges, and a mild lymphocytic dermal inflammatory infiltrate.
- A multifactorial disease influenced by both genetic and environmental factors
- It is not clear whether the infantile and adolescent/adult forms share a common etiology or whether they are distinct disorders.