Introduction

The colour of normal skin comes from a mixture of pigments. Untanned Caucasian skin is pink, from oxyhaemoglobin in the blood within the papillary loops and superficial horizontal plexus. Melanin blends with this colour, e.g. after a suntan. Melanin is, of course, also responsible for the shades of brown seen in Negroid skin. Other hues are caused in addition to these pigments is yellow from carotene, found mainly in subcutaneous fat and in the horny layer of the epidermis.

Cause and Types of Hyperpigmentation

There is no single cause that is responsible for the hyperpigmentation in skin. There are different causes for different types of lesions which are discussed as below:

Freckles

Freckles are most commonly observed hyper pigmented lesions. They are seen most often in the red-haired or blond person as sharply demarcated light brown-ginger macules, usually less than 5 mm in diameter. They multiply and become darker with sun exposure.

Causes

• Freckles can be found on anyone; however it can be genetic and is related to the presence of the melanocortin-1 receptor MC1R gene variant.
• The formation of freckle is triggered by exposure to sunlight exposure to UV-B radiation activates melanocytes to increase melanin production, which can cause freckles to become darker and more visible.

Clinical Course

• Freckles are rare on infants and more commonly found on children before puberty.
• Predominantly found on the face, although may appear on sun exposed areas such as arms or shoulder.
• They are seen most often in the red-haired or blond person as sharply demarcated light brown-ginger coloured macules, usually less than 5 mm in diameter.
• They multiply and become darker with sun exposure.

Treatment

No treatment is necessary; just should avoid sun over exposure and use sunscreen.

Lentigo

A lentigo (plural: lentigines) is a small pigmented spot on the skin with a clearly-defined edge, surrounded by normal-appearing skin. They are light or dark brown macules, ranging from 1 mm to 1cm across. It is harmless hyperplasia (increased number) of melanocytes. The different types of lentigines are:

1. simple lentigo
2. senile or solar lentigo
3. multiple lentigines

Simple lentigo

1. Also known as lentigo simplex.
2. Most common form of lentigo.
3. Arise most often in childhood.
4. Often on areas not exposed to sun, including the mucous membranes.

Senile or solar lentigo

1. Occurs mostly after middle aged.
2. Also known as liver spots or age spots.
3. They are associated with sun exposure and aging.
4. They range in colour from light brown to red or black and are located in areas most often exposed to the sun, particularly the hands, face, shoulders, arms and forehead, and the scalp if bald.

Multiple lentigines

Some syndromes featuring multiple lentigines are:

1. Peutz-Jeghers Syndrome
2. Cronkhite-Canada Syndrome
3. Leopard Syndrome

Treatment

• Treatment is usually not necessary.
• Melanin specific high energy lasers (e.g. pigmented lesion dye laser, 510 nm; Q-switched ruby laser, 694 nm; Q-switched alexandrite laser, 755 nm) are extremely effective for treating ugly lesions.
• Liver spots associated with actinic damage lighten or clear with the daily application of 0.1% tretinoin cream or 2%-4% hydroquinone.

Chloasma

Chloasma is a patterned pigmentation of the face occurring in women during pregnancy or when taking oral contraceptives. The areas of increased pigmentation are well defined, symmetrical and their edges are often scalloped.

Clinical course

• Most of the extra melanin lies in the epidermis, but there is some in the dermis too, making treatment more difficult. If the area is viewed under Wood’s light, an increase in contrast or in pigmentation suggests mainly epidermal pigmentation, whereas loss of contrast suggests dermal pigment.
• The light brown colour becomes darker after exposure to the sun.
• Placenta may secrete hormones that stimulate melanocytes. Chloasma should be differentiated from a phototoxic reaction to a scented cosmetic or to a drug.

Treatment

Treatment is unsatisfactory, although some find bleaching agents that contain hydroquinone helpful. The optimal effect is achieved with preparations containing 2-5% hydroquinone, applied for 6-10 weeks. After this, maintenance treatment should be with preparations containing no more than 2% hydroquinone. A sunscreen will make the pigmentation less obvious during the summer and will minimize the chance of spread.

Nutritional hyperpigmentation

Any severe wasting disease, such as malabsorption, AIDS, tuberculosis or cancer, may be accompanied by diffuse hyperpigmentation. Kwashiorkor presents a mixed picture of generalized hypopigmentation and patchy postinflammatory hyperpigmentation, and in this condition the hair is red-brown or grey.

References

1. Hann, S-K. and Nordlund, J.J. (2000) Vitiligo. Blackwell Science, Oxford.
2. Nordlund, J.J., Boissy, R.E., Hearing, V.J., King, R. Ortonne, J-P. (1998) The Pigmentary System. Oxford University Press, New York.
3. Taylor, S.C. (2002) Understanding skin of color. Journal of the American Academy of Dermatology. Suppl. 46/2.
4. Robbins and Cotran Pathologic Basis of Disease Elsevier. 2005. Page 1232.
5. clinical dermatology(hunter J,savin J,dahl-M)2002 3rd ed.