Abstract
Malassezia folliculitis and Pityriasis versicolor are studied mycologically and histopathologically.
Positive rates of Pityrosporum spp., both by direct examination and culture study of follicular contents were very much higher in Malassezia folliculitis than in acne vulgaris or steroid acne. Pityrosporum was also increased in the normal looking skin of patients with Malassezia folliculitis compared to acne vulgaris, steroid acne and controls. Histopathologically, clusters of spores of the orbiculare type were seen in the dilated infundibula in Malassezia folliculitis.
In the hair follicles of Pityriasis versicolor, hyphae were seen only in the orifices and acroinfundibula. However, spores of the orbiculare type were also seen in the infrainfundibula. In two cases, spores were seen continuously from the infrainfundibula to the orifices and transformed into hyphae only in the orifices.
It can be concluded that in Malassezia folliculitis, the increase of spores in the infundibula is important in its pathogenesis, whereas in Pityriasis versicolor, the yeast-mycelial transformation in the orifices plays an important role. In both diseases, normal looking skin also contained fungal elements and was considered to already be in the preclinical stages of the disease.
