Clinicopathologic Features of Progressive Macular Hypomelanosis in Korea

Lee, Hyun Soo; Sohn, Seonghyang; Kang, Hee Young; Lee, Eun So; Kim, You Chan

Abstract

BACKGROUND
Progressive macular hypomelanosis, a disease of uncertain etiology, was first described by Guillet et al. in 1988. It is characterized by asymptomatic hypopigmented macules and patches that appear on the trunk and upper extremities. It is a relatively recently described disorder and more case reports are needed.
OBJECTIVE
The purpose of the study was to document the clinicopathologic and ultrastructural features of progressive macular hypomelanosis in Korean patients.
METHODS
Patients who presented to our hospital and were diagnosed with progressive macular hypomelanosis from July 2009 to June 2014 were enrolled in this study. Skin scrapings were taken for fungal tests, and skin biopsy specimens from lesional and normal skin were obtained. Sections of the skin biopsies were stained with hematoxylin and eosin, Brown and Brenn Gram stain, and Fontana-Masson stain, and they were incubated with a panel of immunohistochemical reagents used to identify melanocytes, namely, gp-100, melan-A, and microphthalmia-associated transcription factor. The tissues from two patients were also examined using electron microscopy.
RESULTS
Over the course of 5 years, 16 patients presented with ill-defined hypopigmented macules on their trunks and upper extremities. The mean age of the patients was 28.4+/-9.0 years and the male to female ratio was about 1 : 4. Histopathologically, lesional skin showed a reduced level of pigmentation, while the number of melanocytes was preserved. None of the patients showed bacterial colonization of the pilosebaceous units. Electron microscopy demonstrated smaller and less melanized melanosomes in the lesional keratinocytes.
CONCLUSION
Progressive macular hypomelanosis is a hypopigmentary disorder that is characterized by a loss of melanosomes without damage to the melanocytes. Although there are several reports that describe a possible relationship between Propionibacterium acnes and progressive macular hypomelanosis, it remains unclear.