SUMMARY.— The pathogenesis of alopecia areata was studied by plucking hairs from each of a series of concentric zones, using felt patterns placed over lesions. It was possible to group lesions according to the zone with the greatest proportion of club hairs. The results are logically interpreted to mean that a wave of hair follicle damage or arrest moves centrifugally from a focal point beyond the area of alopecia. It is suggested that follicles may react in I of 3 ways. Firstly, severe damage may weaken the hair in the keratogenous zone, this being followed by breakage when the weak zone reaches the plane of the scalp; at the same time the follicle is precipitated into catagen and the hair is extruded as an exclamation mark. Secondly, the follicle may be precipitated into catagen with loss of the club in a normal manner, followed by replacement with a dystrophic anagen hair. Thirdly, the follicle may become dystrophic without a catagen phase.
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Eckert et al. (1968) studied this question.