Bone Dysplasia

Bone Dysplasia: Cartilage and Bone Disorders

There are hundreds of different bone disorders which affect growth. They are mostly rare and often inherited. They are known as skeletal dysplasias. The most common one is Achondroplasia.


Physical characteristics include short upper arms and thighs, a normal length back, a large head, and a depressed nasal bridge, small nose and large forehead.

Those with this condition appear to have large muscles for their leg length. Intelligence and general health are not usually affected.

Achondroplasia is caused by a mutation of a single gene and has a dominant pattern of inheritance. This means that, for adults with the condition, there’s around a 50% chance of any children you have also being affected. However, most cases are caused by a new mutation, without any family history, and this particular gene seems to be one of the most unstable in the human make-up.


This is a similar syndrome, with less noticeable physical characteristics and short stature. Like Achondroplasia, short stature is because of the short legs. The face doesn’t look out of the ordinary (although it has some tell-tale features if you know what to look for) and children with Hypochondroplasia may often be simply diagnosed as ‘just very short.’

Hypochondroplasia is also inherited as a dominant gene, but it seems to be separate from the Achondroplasia gene in that the two very seldom appear in the same family. With Hypochondroplasia, one of the parents often has the disorder.

Definite, confirmed diagnosis can often be tricky. The most helpful feature is comparison of sitting-height and leg-length centiles. While in Achondroplasia the x-ray signs are marked and characteristic, in Hypochondroplasia they are minimal. Clinical trials are currently evaluating the effectiveness of growth hormone treatment.

Other Skeletal Dysplasias

  • Diastrophic Dysplasia (DTD)
  • Conradi-Hunermann syndrome
  • Pseudoachondroplasia
  • Spondylo-epiphyseal dysplasia (SED)
  • Pseudoachondroplasia

And many more rarer syndromes

More information can be found at RGA and Little People UK


Puberty and the Tanner Stages (pdf)

CGF Measuring Guidelines (pdf)

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