Loose anagen syndrome in one identical twin girl.

Loose anagen syndrome (LAS) is a hair disorder involving insufficient anchoring of the hair follicle to the scalp owing to an autosomal dominant or sporadic mutation in the gene encoding keratin 6. There are three phenotypes of LAS, including type B, which presents in young, light-haired girls as unruly, uncombable hair with diminished growth. We present a 2-year-old girl with LAS type B whose identical twin sister was unaffected. The diagnosis was confirmed with a painless hair pull test proven to contain anagen hairs with ruffled cuticles on trichoscopy, preventing the need for unnecessary referrals and diagnostic tests.