[An unusual cause of alopecia on the scalp].

Alopecia is defined as a congenital or temporary absence of hair or even as total or partial hair loss. Clinical manifestation is more marked on the scalp and it is more common in men than in women. Nevertheless, a set of extrinsic factors may be responsible for scarring alopecia of the scalp, including tumors, infections or even loss of substance secondary to thermal burns. On the basis of these illustrations, we here report three cases of patients with scarring alopecia of the scalp secondary to so-called "atypical" causes. The first case (A) is that of a 6-year-old child presenting with alopecia on the right parietal scalp. In-depth interview with his mother allowed to discover the cause of the loss of substance: cutaneous necrosis following laborious delivery by vacuum extraction. The second illustration (B) shows the case of a 40-year-old woman seen in consultation for cutaneous necrosis of the occipital scalp secondary to chemical burn. The patient reported the application of a chemical product in order to fix hairstyle. Finally, the third case (C) is that of a 27-year old patient followed-up for bilateral frontoparietal alopecia secondary to the application of poisonous plant having, according to her beliefs, nourishing virtues for the hair.