Achondrogenesis refers to a group of rare and extreme skeletal dysplasias.
The estimated incidence is 1:40,000 with no recognized gender predilection.
It is classified as an osteochondrodysplasia, meaning deficiency of both bone and cartilage development.
There are several recognized subtypes:
- type 1
- type 2: Langer-Saldino achondrogenesis
Mutations in the SLC26A2 and COL2A1 genes cause achondrogenesis types 1B and 2, respectively. The genetic cause of achondrogenesis type 1A is still unknown. The patterns of inheritance are autosomal recessive in types 1A and 1B, and autosomal dominant with de-novo mutations in type B.
Sonographic diagnosis may be possible after 13 weeks of gestation, where nuchal edema may be evident as an early (though non-specific) sign.
The fetal bony structures are often unable to be identified. There may also be extreme micromelia . Calvarial ossification may be preserved with the type II subtype which can, in turn, give a floating head appearance.
Additional sonographic findings include:
- frontal bossing
- flat face
- anteverted nares
- long philtrum
- narrow fetal thorax
- lung aplasia/hypoplasia
- rib fractures may be present in type 1A
Other ancillary sonographic features that may be present include:
Treatment and prognosis
The prognosis is generally poor, with most infants being stillborn or dying soon after birth.
History and etymology
M Fracaro first described a case of achondrogenesis in 1952.
- achondroplasia: a common cause of dwarfism; not to be confused with achondrogenesis
- Achondrogenesie Typ IA
- Achondrogenesie Typ IB
- Achondrogenesie Typ II
- fehlende enchondrale Ossifikation