Progressive macular hypomelanosis: An update

Abstract

Progressive macular hypomelanosis (PMH) is a common and often misdiagnosed disorder characterized by numerous nummular, coalescing hypopigmented macules on the trunk of adolescents, and young adults. It was originally described in patients with Fitzpatrick skin types V-VI from tropical countries, but is now understood to have a worldwide distribution in a variety of skin types. The pathogenesis of PMH is unknown, but is thought to involve Propionibacterium acnes, which has been found in abundance in the pilosebaceous units of lesional skin. Biopsies of lesions demonstrate normal architecture of epidermis and dermis, but exhibit decreased melanin content. It is important to note that this is different from vitiligo, which has a total absence of melanin. Many patients with PMH often times go misdiagnosed for tinea (pityriasis) versicolor, postinflammatory hypopigmentation, and other dyschromias. Topical antifungal and corticosteroid therapy have proven ineffective in PMH, but successes have been reported with topical and systemic antibacterial treatment modalities and even phototherapy. Given the increasing prevalence of patients with skin of color, it is important to better understand the nature of this condition, along with its diagnosis, management, and treatment.