Skin pigmentation is the term used for describing the colour of the skin. Skin with greater pigmentation (hyperpigmentation) appears dark and skin with lesser pigmentation (hypopigmentation) appears light. The pigment responsible for this colouring is melanin.

Skin pigmentation disorders can be broadly divided as hypopigmentation and hyperpigmentation disorders, which are further classified, on the basis of distribution, as localised or generalised.

The normal pigmentation of the skin can be disturbed due to various factors like heredity, post-injury, auto immune disease, pregnancy and Addison’s disease (which is characterised by hypofunction of the adrenal gland).

Various pigmentation disorders are:

Generalised hyperpigmentation:
It is usually caused due to excessive melanocyte stimulating hormone (MSH) in the circulating blood.

• It is seen in about 95% of patients suffering from Addison’s disease in pressure areas of the skin.
• In about 90% of patients suffering from haemochromatosis. Haemochromatosis is characterised by excessive absorption of iron from the digestive tract.

Localised hyperpigmentation:

• Melasma is patchy hyperpigmentation of the body, mainly face, occurring during pregnancy. Pregnant women are advised to avoid direct sunlight and use sunscreen while going out in the sun. It usually disappears after pregnancy.
• Due to some types of skin cancer like melanoma and basal cell carcinoma.
• Post inflammatory pigmentation which occurs after injury or after some inflammatory skin conditions like eczema.
• Due to prior or current skin infections.
• Due to some benign conditions like melanotic nevi.

Generalised hypopigmentation:

• Albinism is a recessive hereditary disease, characterised by little or no pigmentation in the skin, hair and pupil. Albinism is characterised by many symptoms like blurred or impaired vision, photophobia (sensitivity to light), strabismus (inability to move the eyes together in the same direction) and involuntary back and forth motion of the eyes. Other common problems include easy sunburns and greater chances of developing skin cancers. These problems are attributed to the absence of melanin. Melanin protects the body from the harmful UV radiations of the sun.
• In rare cases, a pituitary dysfunction can lead to acquired generalised hypomelanosis.

Localised hypopigmentation:
This may occur due to partial loss of melanin (achromia) or complete loss of melanin (leukoderma).

• Vitiligo is an acquired disorder causing loss of melanin.
• After an injury or thermal burn
• In leprosy patients, patchy loss of pigmentation is seen
• In pityriasis alba, characterised by several small round scaly pink patches. The condition gets reversed by itself in some months.