Achondroplastic dwarfism is a type of genetic disorder that is a common cause of dwarfism. People with this condition have short stature, usually reaching a full adult height of around 4'0" (1.22 metres). The disorder is a result of an autosomal dominant mutation in the fibroblast growth factor receptor gene 3 (FBFR3), which causes an abnormality of cartilage formation. It occurs at a frequency of about 1 in 20,000 to 1 in 40,000 births.
Clinical features of Achondroplastic dwarfism
* dwarfism (nonproportional short stature)
Description of Achondroplastic dwarfism
People with Achondroplastic dwarfism have one normal copy of the fibroblast growth
factor receptor 3 gene and one mutant copy. Two copies are invariably fatal before or
shortly after birth. Only one copy of the gene needs to be present for the disorder to be
seen. Thus, a person with Achondroplastic dwarfism has a 50% chance of passing on the gene
to their offspring, meaning that 1 in 2 of their children will have Achondroplastic
dwarfism. Since two copies are fatal, if two people with Achondroplastic dwarfism have
children, there's a 1 in 4 chance of it dying shortly after birth; 2 out of 3 surviving
children will have normal Achondroplastic dwarfism. However, in 3 out of 4 cases, people
with Achondroplastic dwarfism are born to parents who don't have the condition. This is
the result of a new mutation.
Achondroplastic dwarfism - Radiologic Findings
A skeletal survey is useful to confirm the diagnosis of Achondroplastic dwarfism. Skull
films demonstrate a large skull with a narrow foramen magnum, and relatively small skull
base. The vertebral bodies are short and cuboidal, and there is congenitally narrowed
spinal canal. The iliac wings are small and squared, with a narrow sciatic notch. The
tubular bones are short and thick with metaphyseal cupping and flaring and irregular
growth plates. Fibular overgrowth is present. The hand is broad with short metacarpals and
phalanges, and a trident configuration. The ribs are short with cupped anterior ends. If
the radiographic features are not classic, a search for a different diagnosis should be
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