Hyperpigmentation (skin darkening) and hypopigmentation (skin lightening) are among the most common skin disorders.
The color of the skin is determined by the presence of a pigment called melanin. The skin cells producing melanin are called melanocytes. Increased number or activity of melanocytes results in hyperpigmentation of the skin, whereas decreased number or activity of melanocytes results in hypopigmentation.
Other factors also play a role in determining the color of the skin. These are vascularity or blood supply of the skin, presence of other skin pigments like carotene and thickness of the skinís upper layer (stratum corneum).
Skin pigmentation disorders usually affect a part of the skin. In some conditions, they can affect the entire skin.
► Post Inflammatory Hyperpigmentation
Skin darkening that follows injury and inflammation is referred to as postinflammatory hyperpigmentation. It often follows conditions like acne, psoriasis, atopic and contact dermatitis, lichen planus, trauma, and fixed-drug eruptions. The resultant hyperpigmentation at the site of injury usually lasts for months or years.
The treatment is difficult and long term; but the condition can be cured with topical creams, medications and laser therapy. Local medications that can be used include corticosteroids, salicylic acid and azelaic acid.
Inflammatory conditions could also result in hypopigmentation in some cases.
In this kind of hyperpigmentation, a tan or a brown patch is seen on the sun-exposed areas of the skin, most commonly the face and forearms. It is also seen in pregnant women; however it disappears after delivery. It is sometimes seen in patients taking oral contraceptives or anticonvulsants like phenytoin. Melasma can be treated topically, and in some cases with laser therapy. Sunscreens help to prevent the development of melasma to some extent.
► Solar Lentigines
Solar lentigines are also called liver spots. They are small hyperpigmented spots that erupt after short-term or chronic exposure to ultraviolet light. They are primarily seen on the face, hands, forearms, chest, back and shins. They are more commonly seen in Whites or Asians.
Ablative or topical therapy is used in treating this kind of hyperpigmentation. Ablative therapies include chemical peels, cryotherapy and laser therapy.
Ephelides or freckles are the small sharp macular lesions of red to light brown color seen on the face, neck, chest and arms. They usually occur during childhood after sun exposure. Treatment is usually not needed as they disappear during the winter months. However, the condition can be treated using local medications.
► Cafe-au-lait- macules
This kind of hyperpigmentation is seen at birth or early in life. They are tan or brown in color, and are often found on the trunk. It can be effectively treated by laser therapy and surgery. More than 6 such lesions should raise the suspicion of the presence of disease conditions like tuberous sclerosis, Albright syndrome, or Fanconi anemia.
This hypopigmentation disorder of the skin occurs due to destruction of melanocytes. It is obvious as smooth, white depigmented patches on the skin. According to the distribution of the patches, it is divided into generalized (all over the body), acral / acrofacial (over the face and ends of the limbs), localized (over a smaller surface area) and segmental (affecting one limb or an area supplied by a single nerve, referred to as dermatome).
Affected people should be protected from sunlight. Other forms of treatments used include topical steroids, immune modifiers, phototherapy and surgical grafting techniques. In some cases where the condition is extensive, depigmentation is advised, wherein the patches of normal tissue are lightened out to match the affected tissue and maintain uniformity.
This is another form of hypopigmentation skin disorder with complete absence of the skin pigment. The color of the hair and skin is also lighter than the normal.
► Pityriasis Alba
Pityriasis alba is a common skin condition that usually affects the face in children. Reddish patches with scaling appear on the face, which subside resulting in hypopigmentation. The skin color returns to normal in due course.
► Tinea Versicolor
Tinea versicolor is a fungal infection of the skin. The skin shows the presence of multiple white spots that are white and scaly. The spots may increase in size with time. People with oily skin, those who sweat a lot or who have decreased immunity may be more prone to developing tinea versicolor. The condition is treated with antifungal medications.
► Treatment-induced Hypopigmentation
Medications and treatments used to treat various skin conditions could result in lightening of the skin. These include dermabrasion, use of chemical peels, and local steroids injections.