Idiopathic subperiosteal new bone formation is uncommon in childhood. We report a case of diffuse periostitis in association with hypergammaglobulinemia and hypoalbuminemia in a 12-year-old boy. In 1966, 2 cases of idiopathic periosteal hyperostosis with accompanying dysproteinemia were documented. This report serves as a review of this unique and perplexing problem in clinical diagnosis.