Special cells in the skin called melanocytes produce melanin. Melanin gives rise to skin pigmentation, or coloring. Disorders of melanin can be characterized by increased melanin production causing skin to get darker (hyperpigmentation) or by decreased melanin production causing skin to get lighter (hypopigmentation). Skin disorders resulting in hypopigmentation may be acquired or congenital (present from birth). Acquired causes of hypopigmentation are more common than congenital causes of hypopigmentation. Collectively, the group of diseases is referred to as skin pigmentation disorders. Twelve skin pigmentation disorders include…
1. Postinflammatory Hyperpigmentation
Postinflammatory hyperpigmentation (PIH) is common and represents darkening of the skin in an area of prior injury or inflammation. The lesions may be described as irregular, darkly pigmented macules and patches. The lesions may persist for months to years. Conditions such as acne, psoriasis, atopic and contact dermatitis, lichen planus, trauma, drugs, and fixed-drug eruptions may lead to postinflammatory hyperpigmentation. It may also occur after laser therapy for other skin lesions. Dark skinned individuals are at higher risk for developing the condition.
Treatment of PIH is often difficult and requires prolonged courses of therapy with excellent patient compliance. Therapeutic agents for PIH include hydroquinone 3-percent or 4-percent (Eldoquin Forte) twice daily, azelaic acid 20-percent cream (Azelex) twice daily, salicylic or glycolic acid peels, retinoids (Retin-A, Tazorac), and laser therapy. Monotherapy seldom gives acceptable clinical results. A clinical trial found serial glycolic acid peels in addition to hydroquinone 2-percent/glycolic acid 10-percent combination twice daily and tretinoin 0.05-percent (Retin-A) at bedtime resulted in faster skin lightening without significant adverse effects.