It is also known as melasma and used for a pattern of asymptomatic superficial brownish pigmentation seen mainly in females. The lesions are usually seen on the bridge of the nose, cheeks, upper lip and forehead. On the forehead, a linear area just above the eyebrows is common. The lesions are usually bilateral and often symmetrical. They become more prominent after sun exposure. Usually the lesions appear during pregnancy but have also been seen in unmarried girls and males, females who have disturbed menstrual cycle, have been taking contraceptive pills since long are at increased risk of developing Chloasma.
Etiology of Chloasma
Chloasma is caused by proliferation of melanocytes and increased production of melanosomes. The tendency to suffer from Chloasma is inherited. Some females begin to experience the condition as a result of puberty-induced hormonal rises. In others, the hormonal changes of pregnancy are the probable cause.
Melanocyte possesses estrogen receptors that stimulate hyperactivity. Both estrogen and progesterone stimulate melanogenasis through this mechanism, and both are elevated during pregnancy. Ingestion of oral contraceptive pills and estrogen supplements produces Chloasma through the same mechanism.
Chloasma Is exacerbated by sun exposure, which accounts for its heightened incidence in those who receive greater amounts of UVB radiation. The etiology in males is less well understood, but is not thought to be related to hormonal causes; it may be testicular resistance.