Ayako Ito, Kazunari Sugita, Hiroyuki Goto, Osamu Yamamoto
DOI: 10.2340/00015555-3519

The pathogenesis of seborrhoeic dermatitis is controversial and remains unclear. Malassezia is considered to be a commensal fungi and is found not only in the stratum corneum but also in hair follicles. It is an important pathogenic factor in seborrhoeic dermatitis. The aim of this study was to clarify the pathogenesis of seborrhoeic dermatitis, morphologically, through comparison with psoriasis vulgaris. Fifteen cases of seborrhoeic dermatitis, 7 of psoriasis, and 6 of normal skin were examined using routine histopathology, immunohistochemistry, and electron microscopy. Macrophages were found to be diffusely distributed in the upper dermis of seborrhoeic dermatitis and psoriasis. In contrast, a significant increase in the number of dendritic cells in the follicular epithelium and dendritic cell clusters in the perifollicular dermis were found only in seborrhoeic dermatitis. Ultrastructural examination of the clusters demonstrated that dendritic cells interacted with lymphocytes, macrophages, and other dendritic cells. In conclusion, folliculotropic distribution of dendritic cells as well as dendritic cell-immune cell clusters play an important role in the pathogenesis of seborrhoeic dermatitis.

Seborrhoeic dermatitis is a common refractory skin disease. The causal factors and disease mechanisms are unknown. The aim of this study was to investigate the morphology of seborrhoeic dermatitis. It was found that dendritic cells, which could control several immune-related cells, had a unique distribution in the skin and formed cell clusters around hair follicles. It was also shown that there was a strong interaction of dendritic cells with other inflammatory cells in the clusters. These suggest the central role of dendritic cells and hair follicles in the aetiology of seborrhoeic dermatitis. This knowledge may be used in developing treatments for the disease.