Dense Bone Dysplasias with Normal Bone Shape

This chapter discusses dense bone dysplasias with normal bone shape and includes discussion on osteopetroses, Raine dysplasia, infantile osteopetrosis, osteopetrosis (intermediate), osteopetrosis (late onset forms), osteopetrosis with renal tubular acidosis, dysosteosclerosis, pyknodysostosis, osteomesopyknosis, osteopetrosis (lymphedema, ectodermal dysplasia, immune defect), osteopoikilosis, melorheostosis, and osteopathia striata with cranial sclerosis. Osteoclasts play important roles during bone growth and in maintaining bone health and bone homeostasis. Dysfunction or lack of osteoclasts is under the control and interaction of many genes and leads to increased bone mass and osteopetrosis phenotypes. Increased bone density in osteopetrosis is also accompanied by some loss of modelling resulting in widening of the affected sclerotic transverse striations. The intermittent nature of the sclerosis results in areas of normal bone density and normal modelling in between the sclerotic bands. The mechanisms related to the apparent “switching off” of the abnormal osteoclastic activity has not yet been elucidated. Most of the conditions in this section are related to a failure of osteoclast function. Each condition discussed includes major radiographic features, major clinical findings, genetics, major differential diagnoses, progress, complications and potential therapies, and a bibliography.