Frictional Alopecia in a Child: An Uncommon Presentation of Lower Limb Hair Loss

Sir, A 6 year-old male child presented to the dermatology outpatient department with patchy loss of hair in the bilateral lower limb. He has a history of similar lesions 1 year back as reported by the parents. Personal history revealed a history of atopy in the child. Otherwise, the child was healthy, going to school, and had no history of patchy alopecia of the scalp. Family history was noncontributory. On clinical examination, the child had multiple patches of alopecia of variable size on the anterior aspect of the bilateral shin areas, the lateral aspect of the legs [Figure 1a], and the posterior aspect as well [Figure 1b]. Dermoscopic evaluation with a Heine delta 30 dermoscope revealed decreased hair density, black dots, broken hair, hair shaft length variability, and bending of hair shafts [Figure 2a]. Along with that few areas showed evidence of excoriation with red-brown hemorrhagic spots and collarette of scale in dermoscopy [Figure 2b]. The thyroid profile of the child was within normal limits. The parents have reported a history of cross-legged sitting while studying and occasional rubbing. A provisional diagnosis of frictional alopecia of the lower limb was made, and the patient has been advised of habit reversal techniques and avoidance of cross-legged sitting. The parents have been counseled regarding the disease, the possible causative factors, and the outcome.Figure 1: (a and b) Well-defined patchy nonscaring alopecia (black arrows) in the lower limb of a young childFigure 2: (a) Dermoscopic image with Heine delta 30 polarized mode showing black dot (black circles), hair shaft bending (black arrows), variable hair length (blue arrow). (b) Hemorrhagic spots (yellow square)DISCUSSION Anterolateral leg alopecia is an entity most commonly seen in middle-aged or elderly males and less commonly in females. The terms such as frictional alopecia, socks alopecia, and peroneal alopecia have been used synonymously. The exact pathogenesis is still unknown, but it is postulated that friction due to rubbing with socks, trousers, high ankle boots, or sometimes cross-legged sitting has been associated with the condition.[1] But sometimes it has also been associated with androgenic alopecia, thyroid disorder, and peripheral nerve disease when a frictional cause has not been found.[2] It is usually reported in middle-aged or elderly males; pediatric cases are less or not reported. In our case, it was a pediatric patient, and the habit of cross-legged sitting and rubbing on the area corroborates with the hair loss on the posterior aspect of the legs as well. The differential diagnosis, in this case, was alopecia areata, but we could find broken hairs, bending of the hair shaft, and hair shaft length variability, thus ruling out alopecia areata.[3,4] We also found black dots, evidence of microtrauma in dermoscopy, possibly associated with rubbing or friction. This entity is usually self-resolving, having a benign course. Habit reversal and counseling are the mainstay of therapy. Still, there is a paucity of data on etiopathogenesis, association, and management of such cases, especially in the pediatric population. The disorder is often underreported due to the benign nature of the disease.[5] In our case, there can be a possible association with atopy. Anterolateral leg alopecia should be thoroughly evaluated and investigated for possible etiologies and association. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.