Familial expansile osteolysis is an autosomal dominant bone dysplasia characterized by increased bone remodeling with osteolytic lesions mainly affecting the appendicular skeleton. There is medullary and cortical expansion of the bone without sclerosis, leading to painful and disabling deformities and tendency to pathologic fracture. Clinical features include onset of conductive hearing loss in childhood, premature loss of teeth caused by root resorbtion, and variably increased serum alkaline phosphatase.
Familial expansile osteolysis is caused by heterozygous mutation in the RANK gene (TNFRSF11A; 603499) on chromosome 18q21.
