MedWire News: Melasma in men occurs largely as a result of sun exposure, suggest study findings published in the Journal of the American Academy of Dermatology.
In contrast, in women the condition seems to occur as a result of a combination of factors including sex hormones, genetics, and ultraviolet (UV) radiation exposure.
"Knowledge of the histopathology of melasma is a prerequisite for understanding its pathogenesis," say Eun-So Lee (Ajou University School of Medicine, Suwon, Korea) and colleagues.
"However, the histopathological characteristics of male melasma are not well characterized," they add, although sun exposure and subtle testicular resistance have been suggested as possible causative factors.
To investigate further, Lee and colleagues examined biopsy samples from melasma lesions and adjacent nonlesional skin in eight men and 10 women with the condition. They also examined lesional and nonlesional skin samples from five men and five women with solar lentigo.
The researchers found that male melasma lesions had the highest vascularity of all the skin samples tested (1.19 vs 0.27-0.93% area), which is characteristic of UV radiation associated lesions. The lesion-to-nonlesion ratio was also greater in male melasma compared with lentigo groups.
"In response to UV radiation, human keratinocytes secrete one of the melanogenic cytokines, stem cell factor (SCF)," explain the authors.
"Human fibroblasts also secrete SCF; this suggests the possibility that overexpression of these cytokines by dermal fibroblasts may activate melanocytes in the overlying epidermis," they add.
In agreement with this, both SCF and c-kit (SCF receptor) were significantly increased in samples taken from male melasma lesions compared with the other skin samples.
Of note, the team found no significant evidence of a hormonal contribution to male melasma.
"This study suggests that the key factor in prevention of male melasma is avoidance of sun exposure," conclude Lee et al.
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