Idiopathic Guttate Hypomelanosis (IGH) is a benign and asymptomatic skin manifestation characterized as diffuse hypopigmented macules, or white spots. The size of the lesions varies from 1-10mm, but are most commonly 1-3 mm in diameter. It is most commonly seen in fair-skinned individuals and appears to be related to cumulative sun exposure rather than just age. Interestingly, this condition manifests in women earlier than men, probably because their legs are more exposed. However, as age increases the incidence of IGH in women and in men is the same. IGH can also be seen in older dark-skinned individuals, but usually at more advanced age. The distribution of IGH can be seen along most exposed areas of the body. These include areas of the arms, legs, upper back, and face. Lesions are usually seen first along the anterior portion of the legs and then seen on the arms, back and face.
The classic white spots of IGH are due to a decrease in melanin in the skin. There is evidence of a genetic component as this disease has been known to run in families. As the name suggests, the exact cause of IGH is unknown, but ultraviolet light exposure may play an important role in the cause of IGH.
The diagnosis of idiopathic guttate hypomelanosis is made clinically by visual inspection alone. Biopsies can be done, but are usually unnecessary. Differential diagnoses to consider include pityriasis alba, tinea versicolor, hypopigmented flat warts, and vitiligo.
While this condition is benign, this condition may be visually disturbing to some patients and treatment may be requested. Primary treatment should consist of educating patients on the importance of sun protection as the appearance of IGH points to signs of sun damage. Patients should be encouraged to wear sunscreen on a daily basis and avoid artificial tanning beds. Treatment modalities that may reduce the appearance of IGH include the topical steroids, tretinoin, pimecrolimus and dermabrasion.
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