Perifollicular Inflammation and Fibrosis in Androgenetic Alopecia: Implications for Diagnosis and Treatment - A Comparative Histopathologic and Clinical Study with Normal-Appearing Scalp

This study of 129 androgenetic alopecia (AGA) patients identifies perifollicular infundibulo-isthmic lymphocytic infiltrates and fibrosis (PIILIF) as a significant inflammatory endotype, particularly in patients aged 44 or older with advanced hair loss or treatment resistance. PIILIF was present in 81% of patients and is characterized by CD4-predominant lymphocytes and increased mast cells. The study found that 67% of patients with AGA-PIILIF improved with combination therapies targeting hormonal and inflammatory pathways. The findings suggest that PIILIF contributes to treatment resistance and graft failure in hair transplantation, emphasizing the need for early diagnosis and targeted anti-inflammatory treatments to enhance outcomes.