The coudability sign of alopecia areata: the real story

Conflict of interest: none declared. Inui et al.1 recently reported in Clinical and Experimental Dermatology their detailed study of ‘coudability’, the sign of alopecia areata I described some years ago.2 While their findings were confirmatory (although they didn’t discuss diffuse AA, in which coudability can be diagnostically useful in the absence of ‘exclamation mark’ hairs), the reason I coined the name ‘coudability’ was not the one they gave; in fact it wasn’t even that given in my original text.2 However, now that the characters who might have been embarrassed are no longer with us, whereas I am still (if only just), I feel able to explain the real story of coudability for those who may use the sign and perhaps even more for those who delight in historical comedy. What I found is that many follicles are only partially struck by AA, and their hairs continue growing, producing either super‐long exclamation mark hairs or, when the hair has not snapped off, a full‐length, apparently normal hair, but one with has a thinner section of shaft at the point where the disease has struck (or several, if there have been recurrent episodes). Such hairs are easily seen with a hand lens, but a lazier way to identify them is by pushing the hair inwards towards the scalp, which produces a very obvious kink in the shaft, where it was poorly formed.