‘Coudability’: a new physical sign of alopecia areata

SIR, The diagnosis of classical alopecia areata is simple but problems may arise with diffuse disease, in which the whole scalp may be involved but without discrete patches, and alopecia areata in which the margin of the patch is vague because short and long hairs are mixed. In addition to the characteristic hair stumps and patent follicular orifices there is another feature which may help diagnosis, especially where the margins of the patches are vague. I have used it for many years and it is probably worth reporting as others seem not to know of it. In classical alopecia areata the disorder affects most of the follicles in the patch and the hairs snap off, sometimes (but especially in children) leaving dark dots at the follicular orifices and, more often, the better known and loved exclamation-mark-shaped stumps. In such affected follicles there appears to have been a short period of growth of poor hair which then snaps, the length of the stump being dictated by duration of the period between onset of disease and cessation of follicular growth. (Interestingly, the appearance of the exclamatory stump is a composite of three easily discernible factors: (i) loss of pigment proximally which makes the proximal shaft look narrower than it actually is; (2) splaying of the zone of rupture which looks even wider because of refraction of light; (3) a progressive narrowing of the shaft which is therefore less than suggested by appearances. ) In the more subacute condition and in some follicles which are only affected partially or transiently, the hair can be seen to continue to grow. This results in a short length of poor shaft, partly depigmented and narrowed often with localized splaying where the hair has begun to split. Sometimes a single hair can be seen to be affected several times along its length indicating episodic disease and recovery. More often there is a single area of weakness which corresponds to a single episode and which is the basis of the physical sign I am at last ready to describe. The sign is of a normal-looking hair which easily can be made to kink when bent or pushed inward, the kink corresponding to the shaft defect produced by the episode of alopecia areata. Often such kinks occur 5-10 mm above the scalp, presumably because the follicle is no longer active and the stationary shaft defect has not yet revealed itself by snapping. Less commonly it is because the follicle has recovered but the hair has not yet grown out sufficiently to localize a fracture. After snapping, some of these hairs continue growing and this explains the long exclamation hairs—often up to several centimetres in length—seen occasionally in alopecia areata, but more often found if looked for. When irregularity of shape or vagueness of outline of the lesion causes diagnostic doubt, inward movement of the hair will invariably produce a sharp kink, usually several millimetres from the scalp, which reveals the site of affection of hairs caught by alopecia areata. The follicles of such hairs can be removed with a forceps applied below the kink and usually show the characteristic anagen atrophy. I have not seen such hairs in other diseases. The appearance of the kink gives the hair the shape of a coude catheter (Bailey, Bishop & Morson, 1958). For this reason, and because the adjective 'kinky' has already been applied to the hair in copper deficiency, 'coudability' would be an appropriate term for this sign of the hairs of alopecia areata.