Definition
achondroplasty; osteosclerosis congenita; Parrot's disease (2);
a type of chondrodystrophy characterized by an abnormality of
conversion of cartilage into bone, predominantly affecting the
epiphyses of long bones in which epiphysial growth is retarded and
ceases early, resulting in dwarfism apparent at birth, with short
extremities, but normal trunk; the head is frequently enlarged, with
flattened nose, due to midfacial hypoplasia; autosomal dominant
inheritance. |
Pathology
So what is the cause of Achondroplasia?
A chemical change within a single gene causes Achondroplasia. It
is not caused from anything the parents have done during pregnancy,
the condition has started from a autosomal dominate condition. What
this means is that a new mutation or genetic change has started
during conception. The condition may also be passed on from one
generation to the next; nine out of ten children born with this
condition have average-sized parents. If one parent has
Achondroplasia there is a 50% chance there child will inherit a
single copy of the gene, if both parents have Achondroplasia there
is a 25% chance the child will have a double dominant gene and a 75%
chance of a single Achondroplasia gene: The gene is called
FIBROBLAST GROWTH FACTOR RECEPTOR
An individual with achondroplasia has disproportionate short
stature: the head is large and the arms and legs are short when
compared to the trunk length. This shortness is particularly
noticeable in the upper arms and thighs. Other signs are a prominent
forehead, a flat or even depressed area at the base of the nose
(between the eyes), a protruding jaw, and sometimes poor dental
structure -- the teeth are crowded and the upper and lower teeth may
be poorly aligned.
An adult with achondroplasia usually has an exaggerated forward
curve to the lower spine, which presents a swaybacked appearance.
The legs of a person with achondroplasia almost always become bowed
and the elbows often cannot be straightened completely. Sometimes
the person has limited twisting ability at the elbows. The hands are
short, and the feet are short, broad, and flat. Another sign is
"double" jointedness, caused by lax (loose) ligaments in some
joints. Many achondroplastic children can flex their finger, wrist,
hip, and knee joints to an extreme degree because of ligamentous
laxity. These signs are usually apparent at birth, and
achondroplasia can be diagnosed at that time in most cases.
Intelligence is generally normal.
Affected men average 51.8 inches in height, while women average
48.6 inches. There seems to be little or no relationship between the
height of the parents and the adult height of their children with
achondroplasia
Treatment
At present there is no specific treatment to promote growth in
achondroplasia. Growth-hormone treatment seems to increase the rate
of growth during the first year of treatment, but may not increase
adult height. Surgery to lengthen the legs and arms of people with
achondroplasia is being done on an experimental basis in a few
centers in the US, but it is not a common practice because
complications are frequent and the process is long and arduous
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