This chapter provides an overview on sclerosing bone dysplasia. Osteoporosis is the most common and known condition characterized by an abnormal bone mineral density. The osteopetroses are a heterogeneous group of sclerosing bone dysplasias, marked by the inability of osteoclasts to resorb bone due to defects in the osteoclastogenesis or the acidification of the extracellular compartment. There is a brief discussion on neonatal osteosclerotic dysplasias, such as Blomstrand dysplasia, desmosterolosis, and raine dysplasia. Blomstrand dysplasia is a very severe disorder being lethal during pregnancy or in the neonatal period. The pregnancy can be complicated by polyhydramnios and hydrops may be apparent on prenatal ultrasound. Midface hypoplasia with short nose, depressed nasal bridge and protruding eyes are characteristic facial features. The limbs are short and broad with relatively normal sized hands and feet. Desmosterolosis is a very rare autosomal recessive metabolic disorder characterized by multiple congenital anomalies and elevated levels of the cholesterol precursor desmosterol.