Rare cause of unilateral upper limb weakness in a young adolescent.

Slowly progressing unilateral upper limb weakness in a previously healthy child can occur due to number of causes which requires a thorough history, physical examination followed by radiological examination, electromyography and so on. Among the various aetiologies, a rare condition such as Hirayama disease is one of the differentials to be considered. There has been a wealth of literature reported on this disease and our case is a learning lesson for all paediatricians to be aware of Hirayama disease and its current concepts.