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Idiopathic Guttate Hypomelanosis

Idiopathic Guttate Hypomelanosis1

Idiopathic Guttate Hypomelanosis2

General Information
Idiopathic Guttate Hypomelanosis is the name given to 2 to 5mm flat white spots found on the shins and forearms. ‘Idiopathic’ definition is the cause is unknown, ‘guttate’ means resembling tear-drops, and ‘hypomelanosis’ is referring to the lighter color of the affected areas. Most commonly seen in middle-aged, light-skinned women, but has been increasingly seen in both sexes including older dark-skinned people with a history of long-term sun exposure. Although the cause is unknown, many researchers believe that ultraviolet light plays an important role. Some treatments include medical therapy which are corticosteroids, either topical or intralesional, and retinoids, typically topical tretinoin. Sunscreens are advised because IGH is a marker of sun damage. Avoiding sun tanning earlier in life can avoid this condition because tanning accentuates the process and intensifies the pigmentary contrast. A good alternative to sun tanning is using artificial tanning, dihydroxyacetone-containing topical agents.

Epidemiology
Very common condition to the point of being almost universal in elderly fair-skinned individuals

Etiology
Unknown. However, it is hypothesized that ultraviolet light plays an important role

Pathogenesis
Develops first on the legs of fair-skinned women in early adult life. Later, it may spread to other sun-exposed areas, such as the arms and the upper part of the back.

Clinical
Discrete, angular or circular off-white macules that are 1-3 mm in diameter. Lesions may measure up to 10 mm in diameter

Histology
Epidermal atrophy of the actinic type, a patchy decrease or absence of melanocytes and melanin, flat rete ridges, and basket weave hyperkeratosis

Bibliography
1. “Idiopathic guttate hypomelanosis” (Online). http://www.dermnet.org.nz/colour/guttate-hypomelanosis.html (visited: March 19, 2008) 2. “Idiopathic Guttate Hypomelanosis” (Online). January 2007. http://www.emedicine.com/DERM/topic194.htm (visited: March 19, 2008)

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