Transverse Histological Analysis of Scalp Seborrheic Dermatitis: A Novel Perspective

Seborrheic dermatitis is a chronic inflammatory disease affecting seborrheic areas of the skin, including the scalp. It is often confused with scalp psoriasis due to similar clinical and histopathological features.

This study described microscopic changes in the pilosebaceous unit in seborrheic dermatitis (SDS) using cross-sectional histological sections in order to improve diagnostic accuracy in differentiating SDS from scalp psoriasis and early-stage alopecia.

This study included 35 men aged 18-65 diagnosed with SDS (both mild and severe cases). Scalp biopsies were obtained and analyzed for 35 microscopic parameters, including quantitative and qualitative variables, and compared with the data of scalp psoriasis from a previous study.

Among 35 scalp biopsies from seborrheic dermatitis (SDS) cases, no significant histological differences were observed between mild and severe forms. Sebaceous gland atrophy was absent in SDS but present in 40% of 22 psoriasis cases, which also showed significantly smaller gland size (0.22 vs. 0.51 mm; p < 0.05). Perifollicular inflammation and fibrosis were common in SDS, while Malassezia yeasts and Demodex mites were rarely identified.

The small sample size and lack of longitudinal follow-up limit the generalizability of the results. Additionally, only scalp biopsies were analyzed, excluding other affected areas.

The findings emphasize that the absence of sebaceous gland atrophy is a useful criterion in the differentiation of seborrheic dermatitis from psoriasis of the scalp. They also highlight the diagnostic complexity of SDS with histological features that could be confused with some scarring alopecias, especially fibrosing alopecia in a pattern distribution.