BH21 Segmented heterochromia with calibre change: an under-recognized sign of alopecia areata

Abstract A 37-year-old woman with a history of recently regrown patchy alopecia areata (AA) presented with increased hair shedding and hair colour changes. She had observed intermittent bands of lighter hair colour within otherwise normal black hairs. The patient had a history of atopy and was diagnosed with iron deficiency 3 years prior, treated with supplementation, but ferritin levels were normal at the time of presentation. She denied dyeing her hair. Trichoscopy and light microscopy revealed sections of lighter hair colour along individual hair shafts associated with decreased calibre of the fibre within these areas. Strikingly, the hair fibres returned to normal diameter where her normal black hair colour resumed. Segmented heterochromia describes lighter bands of colour along the same hair shaft and is mainly associated with intermittent iron deficiency anaemia. However, changes in hair calibre are not described in this condition. In contrast, the combination of lighter hair pigmentation and reduced hair shaft calibre is sometimes observed close to the scalp in some longer hairs affected by AA. In 1984 Shuster coined the term ‘coudability’ to describe the sign of easy hair shaft kinking in these hairs when they are pushed towards the scalp (Shuster S. ‘Coudability’: a new physical sign of alopecia areata, Br J Dermatol 1984; 111: 629). The name is derived from the elbow-shaped bend in the affected area of the hair, reminiscent of tip of a coude urinary catheter. We present this case as an uncommon variant of the coudability hair, where the ‘on–off’ changes observed represent the effects of an intermittent low-level inflammatory process on the hair follicle on a background of diffuse AA. Observation of this sign suggests ongoing disease activity and should prompt additional therapy to prevent disease progression.