Editor,— A 57 year old man presented with a spontaneous posterior dislocation of his right shoulder. It had happened as he reached up to open an overhead cupboard door. He had first dislocated it eight weeks before, while an inpatient receiving chemotherapy for a brain tumour.

He was accompanied by his daughter. When asked she admitted having dislocated both her shoulders in the past. From the history these seemed to be spontaneous dislocations. As there appeared to be a familial tendency she was asked about other members …