Guttate hypomelanosis, attributable to long-term sun exposure, is seen frequently on the forearms and shins of women older than 40 years. It is differentiated from the depigmentation that is characteristic of vitiligo, which has a predilection for periorifacial and genital areas. Tinea versicolor, which is associated with scale, usually arises on the trunk. Some healed factitial lesions feature depigmentation caused by scarring, which was absent on this patient. Cutaneous drug reactions usually are more diffuse than this patient’s rash; hormone replacement agents, also a possible suspect, are not photosensitizing.