The Histopathology of Alopecia Areata in Vertical and Horizontal Sections

In 2001, David A. Whiting's study on the histopathology of alopecia areata (AA) analyzed 494 scalp biopsies and highlighted the diagnostic benefits of using horizontal sections. The study found that AA patients had about 25% fewer follicles than controls, with an average of 30 hairs per 4 mm punch biopsy, including an abnormal terminal:vellus ratio of 1.3:1 and an anagen:telogen ratio of 62:38. Key histopathologic features of AA included peribulbar and intrabulbar mononuclear infiltrates, degenerative changes in the hair matrix, and increased numbers of miniaturized vellus hair follicles. The sex ratio of AA patients varied with age, and a 21% reduction in follicular counts was observed in patients aged 61-75. Alopecia universalis (AU) showed a 15% reduction in follicular counts compared to other AA types. Horizontal sections were deemed more useful than vertical sections for diagnosing and providing prognostic information in AA, particularly in cases lacking characteristic peribulbar inflammatory infiltrate.