The patient was an apparently healthy, 5-year-old girl who presented marked hair fragility from 7 months of age. Physical examination revealed diffuse hypotrichosis with short, dull, fragile hair associated with areas of erythema and follicular hyperkeratosis (Fig. 1A). The vertex was the least affected area. The hair pull test was negative whereas the traction test was positive. Trichoscopy revealed dystrophic constrictions (Fig. 1B, arrows) regularly separated by eliptical nodes that corresponded to areas of normal hair thickness, giving the hair a beaded appearance. Other findings included mild alopecia of both eyebrows, normal eyelashes, and no alterations of the nails or teeth. In the family history, the patient's mother had a similar condition that had started during childhood and affected the scalp, eyebrows, and eyelashes. At the time of consultation, the mother presented total scalp alopecia and partial repopulation of the eyelashes and eyebrows, with similar findings on trichoscopy (Fig. 1, C and D).

Figure 1

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The diagnosis in our patient was monilethrix, a rare hereditary hair dysplasia that has an autosomal dominant inheritance in the majority of cases. Trichoscopy characteristically shows the “regularly bended ribbon sign”. The diagnosis is confirmed by the detection of moniliform hair on optical or scanning electron microscopy; however, the availability of dermoscopy in outpatients now enables us to make a rapid diagnosis of this condition.