Description

• Seborrheic dermatitis (SD) is a multifactorial skin disease influenced by both host and environmental factors.
• Involves sebaceous areas of the body
  • Including the scalp, face, back, chest, and intertriginous areas
  • Characterized by greasy, yellow, scaly erythematous lesions
• Usually a self-limited condition in infants but can be a chronic, relapsing condition in adolescents and adults

Epidemiology

• Trimodal distribution: infants, adolescents, and adults >50 years of age
• Highest prevalence in first 3 months of life
• Affects approximately 10% of the general population and up to 70% of infants in the first 3 months of life
• No sex predilection in infants; however, in adolescents and adults, males are affected more commonly than females.
• Seasonal pattern: Prevalence of disease increases in winter months.
• Strong association between Malassezia species, a common commensal organism, and SD

Risk Factors

• There are no known genetic factors that contribute to disease.
• Hormonal effects: exposure to maternal estrogen in infancy and surge of androgens in puberty
• Immunocompromised status
  • Impaired cellular immunity may contribute to pathogenesis of disease.
  • Prevalence of SD in immunocompromised patients is significantly higher than in general population.

General Prevention

There are no known preventive measures.

Pathophysiology

• Androgens stimulate sebaceous glands, causing production of more sebum.
• Malassezia
  • A lipophilic yeast that is normally found in sebum-rich areas of the skin
  • Can break down skin sebum lipids, producing potentially inflammatory fatty acids
• In response to the inflammatory fatty acids, keratinocytes produce proinflammatory cytokines.

Etiology

Not completely known, although it was thought that yeast, androgens, and the local host immune response play a role in SD development.