Hypertrichosis is often a prominent feature in children with SURF1 deficiency.38 Excess hair is typically observed on forearms, thighs, shins and upper back. Hair abnormalities (pili torti) have been reported in Bjornstad syndrome, caused by deficiency of the complex III assembly factor BCS1l.39 Interestingly, alopecia totalis has recently been reported in children with deficiency of the complex III subunit UQCRFS1. Here, BCS1L is linked to Bjornstad syndrome.