Osteofibrous dysplasia in a Japanese boy with Costello syndrome.

We present the case of a boy with Costello syndrome who developed osteofibrous dysplasia during a phase of growth hormone therapy. The lesion and the accompanying pain disappeared after discontinuation of the therapy. Growth hormone is a known mitogen for some neoplasms and osteofibrous dysplasia has been reported to become aggressive. Thus, although osteofibrous dysplasia in Costello syndrome has not been reported before, growth hormone therapy should be used under close supervision in children with this syndrome.