achondrogenesis

Neonatal lethal dwarfism characterized by severe bone dysplasia of all four limbs, micromelia, enlarged skull, and a short trunk with delayed or absent ossification of the lower spine and pubic bones. There are various types. [G. a- priv. + chondros, cartilage, + genesis, origin]

- Type IA a. [MIM*200600] a. with hypervascular cartilage and hypercellular bone; uncertain inheritance pattern. SYN: Houston-Harris syndrome.

- Type IB a. [MIM*600972] a. with severely disorganized intracartilaginous ossification; autosomal recessive inheritance, caused by mutation in the diastrophic dysplasia sulfate transporter gene (DTDST) on chromosome 5q. SYN: Parenti-Fraccaro syndrome.

- Type II a. [MIM*200610] a. with autosomal dominant inheritance, caused by mutation in the collagen type II gene (COL2A1) on chromosome 12q. SYN: Langer-Saldino syndrome.

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achon·dro·gen·e·sis (a-kon″dro-jenґə-sis) the severest of the chondrodysplasias, a hereditary disorder characterized by hypoplasia of bone, micromelia, enlarged head, shortened trunk, and deficient or absent ossification of the lower spine and pubis. It is divided into type I (further subdivided into Ia and Ib) and type II, which differ in site of mutation and mode of inheritance; all are lethal before or shortly after birth.