Hyperparathyroidism in the pediatric population typically presents during adolescence, as with this case, and there appears to have higher incidence of bone involvement then adults.16 The effects of hyperparathyroidism on skeletally immature bone and development of sarcoma are not known, but an in vitro study13 suggests that exposure to PTH in younger rats may have a higher risk for sarcoma development than in rats exposed later in life. The gene discussed is PTH; the disease is sarcoma.