Retronychia is a rare onychopathy, occurring in young adults. It is due to a conflict between the nail plate and the proximal supra-nail fold. Favouring factors are predominantly microtrauma. The diagnosis is clinical and confirmed by surgical avulsion, which also has therapeutic value. We report a case of retronychia of the nails of the right hand in a 22 year old man, following immobilisation with a right anterobrachial-palmar cast.