Histopathological characterization of inflammatory interparietal involvement in frontal fibrosing alopecia.

Introduction: Frontal fibrosing alopecia (FFA) may involve the interparietal area; however, histopathologic features in this site remain undefined. Objective: The objective of the study was to histopathologically characterize inflammatory interparietal involvement in patients with FFA in real-world practice. Methods: A descriptive, retrospective study enrolled patients with FFA who developed interparietal inflammatory findings. Patients underwent two interparietal biopsies; samples were assessed under a uniform protocol, which included follicular counts, inflammatory infiltrate features, scar tissue, vacuolar degeneration (VD) of the follicular epithelium, epithelial or stromal (E/S) clefting, concentric lamellar fibroplasia (CLF), and sebaceous glands (SGs). Results: A total of 12 females (mean age: 64.25 years) were included. Following dermatopathologic review, six patients were classified as having crown-area FFA (CA-FFA), four patients as having fibrosing alopecia with a pattern distribution (FAPD), and two patients as having indeterminate cicatricial alopecia. CA-FFA showed greater structural loss with scar tissue and sebaceous gland reduction, whereas FAPD showed a miniaturization-dominant profile and increased catagen/telogen hairs. Patients with a biopsy suggestive of CA-FFA more often had a diffuse clinical pattern, were older, had a longer disease duration, and had approximately twice as much occipital involvement than as those in the FAPD group. Discussion/Conclusion: Given that FFA produces greater structural disruption than FAPD, our results raise the question of whether these conditions are overlapping entities or part of the same process that has progressed. Further studies in patients with FFA and FAPD are needed to elucidate the role of androgenetic factors in addition to lymphohistiocytic infiltrate and perifollicular lamellar fibrosis.