Achondrogenesis

Achondrogenesis refers to a group of rare and extreme skeletal dysplasias.

The estimated incidence is 1:40,000 with no recognised gender predilection.

It is classified as an osteochondrodysplasia, meaning deficiency of both bone and cartilage development. 

Subtypes

There are several recognised subtypes:

Genetics

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.

Antenatal ultrasound

Sonographic diagnosis may be possible after 13 weeks of gestation, where nuchal oedema 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 5. Calvarial ossification may be preserved with the type II subtype which can, in turn, give a floating head appearance.

Additional sonographic findings include:

Other ancillary sonographic features that may be present include:

The prognosis is generally poor, with most infants being stillborn or dying soon after birth.

M Fracaro first described a case of achondrogenesis in 1952.

General considerations for mild cases include hypochondrogenesis. For absent calvarial bone(s) (type 1A/1B) on antenatal ultrasound, consider acrania.

  • achondroplasia: a common cause of dwarfism; not to be confused with achondrogenesis
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Article information

rID: 13275
Section: Syndromes
Tag: cases
Synonyms or Alternate Spellings:

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