Aetiology

• precise cause of melasma is unknown
  
  
• aetiological factors include:
  • genetic and racial influences
    • increased incidence in individuals of Hispanic origin who live in areas receiving high-intensity UV radiation (1)
    • there is also a tendency for individuals with brown skin in Sri Lanka, India, the Philippines and Middle Eastern countries to develop melasma at an early age
    • there is a family history of melasma in upto 30% of cases (1)
  • exposure to ultraviolet radiation
    
    
• oestrogen/progesterone therapies
  • the incidence of melasma increases with the length of time for which the contraceptive has been taken (2). The incidence associated with the oral contraceptive pill is unknown but varies from 9% to 37%, with the higher incidence associated with sunnier climates (2,3,4)
    
    
• pregnancy (7)
  • 90% of pregnant women have increased skin pigmentation, and 5% to 70% have chloasma (the 'mask of pregnancy'), i.e., reversibly increased skin pigmentation in the face, on the dorsum of the nose, and on the eyelids
    • probabilty of chloasma depends on
      • sunlight exposure,
      • genetic predisposition,
      • and skin type
• Other aetiological factors that have been reported include cosmetics and phototoxic antiepileptic drugs, especially phenytoin (5,6).
  
  
  
  
  
  
  
  
  
  
  
  

Reference:

• (1) Pathak MA et al (1985). Usefulness of retinoic acid in the treatment of melasma. J Am Acad Dermatol, 15, 894-899.
• (2) Carruthers R (1966). Chloasma and oral contraceptives. Med J Aust, 2, 1-20.
• (3) Resnik S (1967). Melasma induced by oral contraceptive drugs. JAMA, 199, 95-99.
• (4) Sanchez NP et al (1981). Melasma; a clinical, light microscopic, ultrastructural and immunofluorescence study. J Am Acad, 4, 698-710.
• (5) Smith AG et al. Chloasma, oral contraceptives, and plasma immunoreactive beta-melanocyte-stimulating hormone. J Invest Dermatol, 68, 169-70.
• (6) Lufti RJ et al (1985). Association of melasma with thyroid autoimmunity and other thyroid abnormalities and their relationship to the origin of melasma. J Clin Endocrinol Metab, 61, 28-31
• (7) Mackensen F, Paulus WE, Max R, Ness T.Ocular changes during pregnancy. Dtsch Arztebl Int. 2014 Aug 18;111(33-34):567-75; quiz 576.