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Disorders of pigmentation 

Disorders of pigmentation
Disorders of pigmentation

Eugene Healy

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date: 08 December 2019

Normal human skin colour results from the reflection of light from haemoglobin in blood, and carotenoids and melanin pigmentation in skin. The melanin pigmentation is the major component determining differences in skin colour between races.

Increases and decreases in skin pigmentation (hyperpigmentation and hypopigmentation, respectively) may be localized or generalized, can result from a wide variety of physiological or pathological processes, including both genetic and acquired factors, and may reflect underlying systemic disease.

Addison’s disease (primary adrenocortical hypofunction) can result in diffuse hyperpigmentation, more pronounced in sun-exposed areas, sites exposed to trauma, such as the elbows and knees, the creases of the palms and soles, surgical scars, the buccal and gingival mucosa, as well as the nipples and genital region. Numerous drugs can cause changes in pigmentation, e.g. amiodarone can cause a blue-grey discolouration of the skin whereas bleomycin can cause a flagellate pattern of hyperpigmentation.

Vitiligo is characterized by white patches of variable size, but in some darker-skinned people the margin or entire patch may be an intermediate colour of light brown (trichrome vitiligo). Patches may be generalized or segmental in distribution, and the borders are irregular. In the generalized form lesions are usually symmetrical, and the more frequently involved sites are around the orifices (eyes, nose, mouth), flexures (axillae, groins, genitals), and extensor surfaces (elbows, knees, digits). The isomorphic or Koebner phenomenon can occur, in which trauma to the skin can produce lesions at that site. The skin is usually normal otherwise, with no evidence of scaling or atrophy.

Microbial diseases such as pityriasis versicolor, leprosy, and syphilis are important infectious causes of hypopigmentation. Irrespective of cause and associations with underlying systemic disease, disorders of pigmentation can cause considerable distress to sufferers due to the visible nature of this condition.

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