Epidermal Langerhans cells in erythrokeratodermia variabilis. Histochemical and ultrastructural investigations before and after treatment with etretinate (RO 10-9359).

The distribution of epidermal Langerhans cells (LC) in erythrokeratodermia variabilis (EKV) was investigated using enzyme-histochemical (ATPase) and immunohistochemical (anti-T6 and anti-HLA-Dr) techniques. Biopsy specimens from lesional skin of five patients were examined before and 8 weeks after treatment with etretinate (RO 10-9359). In addition, electron microscopy studies were carried out in two of these cases. The number of ATPase-positive dendritic cells in lesional epidermis appeared to be remarkably reduced in comparison with normal skin from healthy subjects. After treatment, the number of ATPase-positive dentritic cells had increased but still remained below normal values. Similar but less striking results were found for anti-T6-stained specimens. The HLA-Dr antigen appeared to be unsuitable as a marker for comparative quantitative studies because of the highly variable expression of this antigen in the control specimens. Electron microscopy studies revealed LC in the basal and suprabasal layers of the lesional epidermis. Both before and after treatment, the LC exhibited a normal ultrastructure. In view of the clinical and histologic normalization of the skin lesions during treatment, these findings suggest that the decreased number of epidermal LC may be related to the abnormal keratinization that occurs in EKV.