Idiopathic Guttate Hypomelanosis

After more than 15 years of wondering what the “white specks” on his legs were, a 64-year-old man consulted his physician. The patient was taking medication to control hypertension; he was otherwise healthy.

The lesions were 2- to 5-mm, sharply marginated, cream- to white-colored macules. Distributed all over his legs, the lesions were particularly dense on the shins.

Based on the lesions' clinical appearance, Drs Charles E. Crutchfield III and Humberto Gallego of St Paul diagnosed idiopathic guttate hypomelanosis. This disorder affects approximately 40% of persons in their 40s, 50% of those in their 50s, and more than 70% of persons older than 70 years. Hypomelanosis is often overlooked in persons with light complexions; frequently, it can be detected only by Wood's light examination, or it is noticed after sun exposure or tanning. The cause of idiopathic guttate hypomelanosis is unknown.

The macules are found most commonly on the extensor surfaces of the upper and lower extremities. Although idiopathic guttate hypomelanosis has a very characteristic appearance, vitiligo and the confetti lesions of tuberous sclerosis need to be considered in the differential diagnosis.

Treatment options are limited. Some success has been reported after a light liquid nitrogen freeze. The macules are not amelanotic; hence, theoretically, the freezing “angers” the remaining melanocytes enough to initiate melanin production. Longer freezing periods (in excess of 20 seconds) will destroy the melanocytes and produce very long-lasting-perhaps permanent-white macules