Objective: We aim to investigate the morphological features of isolated HFs from AA lesions to understand HF cycling in the pathological process of AA.
Methods: Thirty three patients with AA and ten normal controls were studied. Scalp biopsy specimens were taken from areas of recent active hair loss or at the margin of a hair loss lesion. HFs were then isolated under a dissecting microscope and their morphological structures were then examined in addition to routine histological evaluation.
Results: A high percentage of different phases of the catagen and telogen stage were found in all patients. AA specimens showed HFs in a normal anagen stage were well-shaped with confined pigmentation. HF separated from 7 cases (21%) showed dystrophic anagen with altered structure. One of the features in early catagen of AA is incontinence of pigmentation around and inside ORS in the bulbar area, which was found in 13 cases (39%), which correlated well with features observed histopathologically. During early catagen, the hair shaft started to move away from the dermal papilla (DP) in an upward direction and the bulb became narrower. The DP from an intermediate catagen phase follicle took the shape of a compact ball-like structure and was not completely enclosed by the smaller retracted hair bulb. DP was less condensed and covered with more melanin in AA than in normal catagen, which also correlated well with pathological features. Miniaturized terminal HFs were found in 12 cases (36%) with longer duration of AA.
Conclusion: Melanocytes may be an early target during the progression of AA. Morphological features of isolated HFs from AA lesions correlated well with histopathological features. Study on morphological changes of HF in AA may provide us a three-dimensional view to reveal better the pathological process of AA.