Perifollicular Fibrosis and Inflammation in Androgenetic Alopecia and Seborrheic Dermatitis: Diagnostic Challenges in Differentiation from Fibrosing Alopecia in a Pattern Distribution

This study aimed to differentiate histopathological features of Androgenetic Alopecia (AGA) and Seborrheic Dermatitis (SD) from Fibrosing Alopecia in a Pattern Distribution (FAPD) by examining scalp biopsies from 56 Caucasian male patients. Results showed that AGA is characterized by higher vellus follicle counts and lower terminal follicle and anagen hair counts, indicating follicular miniaturization. Both AGA and SD exhibited frequent perifollicular fibrosis, limiting its specificity for scarring alopecias. Unique to AGA were mild basal vacuolization and eccrine duct dilatation, while polytrichia was exclusive to SD. Perifollicular inflammation was common in both conditions, sometimes resembling lichenoid patterns. The presence of Demodex spp. was more prevalent in AGA. Despite the study's limitations, including a small sample size and lack of FAPD comparison, it highlights the significant histopathological overlap between AGA, SD, and FAPD features, emphasizing the need for careful clinicopathological correlation to prevent misclassification.