Leukoderma induced by Rhododendrol is different from leukoderma of vitiligo in pathogenesis: a novel comparative morphological study

Background

Rhododendrol (Rhododenol®), an inhibitor of tyrosinase activity, is used as a skin‐whitening component. Many cases of leukoderma after the application have been reported, termed Rhododenol‐induced leukoderma (RIL). The aim of this study was to clarify the pathogenesis of RIL morphologically through comparison with vitiligo.

Methods

We examined 14 cases of RIL and 15 cases of vitiligo using routine histopathology and immunohistochemistry. Thirteen cases of RIL, 6 cases of vitiligo and specimens of the RIL mouse model were evaluated by electron microscopy.

Results

There were common findings in RIL and vitiligo at the light‐microscopic level: a) vacuolar changes in the dermoepidermal junction, b) melanophages in the papillary dermis, c) perifollicular lymphocyte infiltration, d) loss or decrease of basal melanin pigment and e) decrease of melanocytes in the lesions. The ultrastructural observations demonstrated specific findings of RIL: 1) remaining melanocytes in depigmented lesions, 2) inhomogeneous melanization in melanocytes and 3) degenerated melanosomes in melanocytes. Some of the findings were observed in a RIL mouse model. Furthermore, it is notable that cell organelles of melanocytes were intact in our RIL cases.

Conclusions

Morphological changes of RIL targeting melanosomes in melanocytes without degeneration of organelles reflect the reversible clinical course of most cases.

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