How can we differentiate trichotillomania from alopecia areata in children?

Differentiating trichotillomania from alopecia areata 

It can be challenging in some children to distinguish alopecia areata (an autoimmune condition) from trichotillomania (an impulse control disorder whereby individuals pull out their own hair). Sometimes even both coexist in the same patient! 

Exclamation mark hairs are frequently seen in both alopecia areata and trichotillomania and are therefore not specific (arrow). Several dermatoscopic signs, however, are more common in trichotillomania than alopecia areata including flame hairs, split ends, hairs of different lengths, v-sign (shown here with yellow circle), hair powder.