[Ulstrastructural study of various evolutive stages of pityriasis versicolor (author's transl)].

Small size, less numerous and sometimes clustered melanosomes, were seen within the melanocytes. The others organites alos showed abnormalities: smaller mitochondria, abundant cytofilaments. Sometimes total degeneration of the melanocyte was seen. These alterations are variable, depending upon the evolutive stage of pityriasis versicolor: either hypopigmented undergoing treatment or not, or hyperpigmented. Reactions of several cellular types of the dermoepidermal unit could be observed: more numerous Langerhans cells located near the base of the epidermis, abundant nerve fibers in the superficial dermis and active fibroblasts of foetal type. A slight inflammatory infiltrate was present in some cases. It is suggested that a toxic effect of the fungus is responsible for the changes of the morphological aspects of the melanocyte.