Several features are characteristic of alopecia areata. The most helpful is the presence of swarms of lymphocytes in the vicinity of a hair bulb. It is often the case that only a few such foci are seen in a given biopsy, particularly in a 3 mm. diameter punch biopsy. The demonstration of such a focus may require step sectioning the block. Another feature that is helpful is the finding of follicles that appear to be stuck in the what should be the migration from anagen to catagen to telogen positions. The basement membrane of such a follicle is thickened and convoluted, and the fibrous sheath is also thickened. The outer root sheath is shriveled.
 

	Scan power view.
	Low power view of the bottom right part of the image above. Numerous lymphocytes are found near the hair bulb on the left. This is virtually diagnostic for alopecia areata.
	Very low power view of another part of the biopsy. Note the two follicles near the right side of the picture.
	Higher power view of above. The basement membranes are thickened, and there is thickening of the fibrous sheaths. The epithelial components lack glycogen, and the edges are crinkled. Look at the picture above this one to see how the follicle on the right seems stuck in a relatively deep position considering the shriveled state of the follicle.

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