Immunohistochemical analysis of rhododendrol-induced leukoderma in improved and aggravated cases

Background Rhododendrol (RD) is cytotoxic to melanocytes and can cause leukoderma at the application site. Patients with RD-induced leukoderma usually recover after discontinuation of application (improved cases). However, occasionally lesions may expand or new lesions may develop in unapplied sites (aggravated cases). Objective To understand the pathomechanism of RD-induced leukoderma in aggravatedcases. Methods We performed immunohistochemical study to compare the expression of the catalytic subunit of glutamate cysteine ligase (GCLC), E-cadherin, and mast cell tryptase in 22 improved cases, 16 aggravated cases, and 39 normal controls. Results GCLC expression in melanocytes surrounding leukoderma was higher in improved cases than in normal controls and aggravated cases. E-cadherin expression in melanocytes was upregulated both in improved and aggravated cases and increased levels of degranulated mast cells were observed in aggravated cases. Conclusion Our results indicate that downregulation of GCLC expression due to low levels of glutathione along with reduced melanocyte migration and increased E-cadherin expression can aggravate RD-induced leukoderma. Additionally, increased degranulation of mast cells may prolong the persistence of RD-induced leukoderma.