Progressive Macular Hypomelanosis

Progressive macular hypomelanosis (PMH) is a common but under-recognized disorder characterized by multiple non-scaly, nummular hypopigmented macules and patches distributed symmetrically on the trunk and proximal extremities of young adults.¹ The term PMH was first introduced by Guillet in 1988 to describe a dyschromia primarily affecting young women of mixed racial background with Fitzpatrick skin types IV-VI in the Caribbean and West Indies.¹ Although more common in darker skin types, PMH has been reported in patients with skin types I-III in the United States, northern Europe and throughout Asia.^2,3 The exact incidence of PMH is unknown as it is frequently misdiagnosed as tinea versicolor or pityriasis alba. The eruption itself is asymptomatic, with the most common complaints being about cosmesis and the persistent or progressive nature.^1,4 Most patients fail to improve despite repeated trials of topical and systemic antifungals and/or topical steroids. As familiarity with the diagnosis increases and an understanding of its pathogenesis emerges, reports of therapeutic success are growing. We report our experience with five patients with PMH who improved with antimicrobial therapy.

Five young adults, ranging in age from 26 to 29 years old and with Fitzpatrick skin types IV-VI, presented with asymptomatic, hypopigmented non-scaly macules on their trunk and/or extremities. Each patient had developed asymptomatic dyspigmentation over the course of months to years. Three patients had consulted a dermatologist prior to their presentation in our clinic, and had failed to improve despite treatment with systemic and/or topical antifungal therapy. Woods lamp examination of the hypopigmented skin was performed upon initial evaluation and demonstrated perifollicular red fluorescence in hypopigmented lesions in all except one patient, and a clinical diagnosis of PMH was rendered in each case. Histologic examination of lesional and non-lesional skin was performed for one patient (Table 1, Patient 1) and demonstrated that hypopigmented macules had fewer melanocytes and melanophages compared to normally-pigmented adjacent skin. Periodic acid-Schiff staining failed to reveal fungal elements. Patients were treated with oral antibiotics and a topical antibacterial agent for a minimum of six weeks prior to re-evaluation. All patients showed at least partial response to this regimen within two to three months (Table 1). Despite some improvement, antibiotics were discontinued in one patient (Patient 5) at her request and narrow band ultraviolet therapy was initiated with rapid improvement and repigmentation (Figure 1).

The term "progressive macular hypomelanosis" was first employed by Guillet et al. in 1988 to describe this characteristic hypopigmentation within mixed racial populations in the French Caribbean, although there are multiple reports of this entity published under various names including cutis trunci variata in Venezuela, dyschromia creole in the French West Indies, progressive and confluent hypomelanosis of the melanodermic metis, nummular and confluent hypomelanosis of the trunk in the Netherlands, and progressive macular confluent hypomelanosis and idiopathic multiple large macule hypomelanosis in the United States.^1,5-8 PMH was initially thought to exclusively affect patients with Fitzpatrick skin types V and VI from tropical and subtropical climates and the prevalence continues to be highest in populations with darker skin types. However, there are growing reports in recent years of lighter skin patients (Fitzpatrick types I-IV) with PMH in the United States, Europe, Korea, Singapore and China.^1-3,9-11