Part of “CHAPTER 66 – RARE DISORDERS OF SKELETAL FORMATION AND HOMEOSTASIS“

Not all disorders in children that result in widened growth plates and metaphyseal irregularity are forms of rickets (i.e., generalized disturbance of mineralization of skeletal matrix).5 Metaphy-seal or spondylometaphyseal dysplasias may mimic rickets radiographically5; however, the biochemical aberrations associated with rachitic disorders are absent.84 Serum levels of calcium, phosphate, and alkaline phosphatase activity are normal, and biopsy of skeletal tissue away from the metaphyses (after in vivo tetracycline labeling) confirms that bone remodeling is unremarkable. Instead, these disorders involve dysplastic processes occurring in growth plates. They are heritable with various patterns of genetic transmission.1,4,7,84 Mutations in the genes that encode types II, IX, and X collagen have been discovered.