Summary
Dwarfism is a disorder characterised by shorter than normal skeletal growth
that can be genetic.Achondroplasia is a common form of short-limbed dwarfism.
The majority of children born with the disorder have average-sized parents.
On this page:
Symptoms of dwarfism
On this page:
Symptoms of dwarfism
Causes of dwarfism
Common problems during infancy and childhood
Common problems during adulthood
Treatment for dwarfism
Where to get help
Things to remember
Dwarfism refers to a group of conditions characterised by shorter than normal
skeletal growth. This shortness can be manifested in the arms and legs or
trunk. There are over 300 conditions that cause abnormal skeletal growth and
dwarfism. Achondroplasia is the most common type of short-limb dwarfism,
occurring in around one in 25,000 children with both sexes at equal risk. This
type of skeletal dysplasia (abnormal skeletal growth) is usually diagnosed at
birth.
The majority of children born with the disorder have average-sized parents. The
child may experience delay developing motor skills, such as controlling the movements
of the head, but intellectual development is normal in children with
achondroplasia. The average final height for a person with this condition is
130cm for men and 125cm for women. Short-statured people lead normal, fulfilled
lives. Achieving higher levels of education and career and personal ambitions
is not limited by stature.
Symptoms of dwarfism
The characteristics of achondroplasia include:
a trunk of relatively normal length
disproportionately short arms and legs
bowed legs
reduced joint mobility in the elbow
other joints that seem overly flexible, or ‘double jointed’, because of loose
ligaments
shortened hands and feet
a large head
a flat mid-face
crowded teeth, because of small upper jaw
a prominent forehead
a flattened bridge of the nose.
Skeletal dysplasias and dwarfism
Dysplasia means ‘abnormal growth’. There are around 300 different types of
skeletal dysplasias, with achondroplasia being the most common form of
disproportionate short stature. Other skeletal dysplasias can cause short-trunk
disorders and proportionate short stature. A skeletal dysplasia is diagnosed
with a variety of tests, including physical examination, x-rays, tissue and
bone samples, and specific genetic tests.
Causes of dwarfism
About 80 per cent of people born with achondroplasia have average-sized
parents. This means that the genetic mutation that causes achondroplasia occurs
during conception, when the mother’s egg is fertilised by the father’s sperm.
It is not known why this genetic mutation occurs, or how the mutation
translates into the characteristics of achondroplasia. Twenty per cent of
people born with achondroplasia inherit the faulty gene from an affected
parent. If one parent has achondroplasia, then their child has a 50 per cent
chance of inheriting the gene for the condition. If both parents have
achondroplasia, then their child has a one in four risk of inheriting the
faulty gene from both parents, which causes a fatal condition known as ‘double
dominant’ or homozygous achondroplasia. Children born with this variation
generally don’t live beyond 12 months of age.
Common problems during infancy and childhood
The child with achondroplasia faces a number of difficulties, including:
breathing difficulties – including snoring and sleep apnoea (the regular cessation
of breathing during sleep), caused by narrowed nasal passages.
ear infections – caused by narrowed Eustachian tubes (tubes leading from the
ears to the throat) and nasal passages.
bowed legs – the legs are initially straight, but become bow-legged once the
child starts walking. Over time, in some cases, the weight of the child’s body
causes the legs to bow.
increased lumbar lordosis – a backward curve in the lower spine.
reduced muscle strength – the child has softer muscle tone than normal, and
needs to be adequately supported until the muscle groups are ready to support
the neck and spine.
hydrocephalus – the child has an increased risk of hydrocephalus (one in 100),
which is an accumulation of cerebrospinal fluid inside the skull that can lead
to head enlargement.
narrow foramen magnum – the child has a smaller than normal opening at the base
of the skull (foramen magnum), where the spinal cord begins. This can sometimes
press against the brain stem and cause symptoms including apnoea (cessation of
breathing) and neurological signs.
Common problems during adulthood
Problems faced by the adult with achondroplasia can include:
Nerve compression – the nerves in the lower back or lumbar region are squashed,
which can cause symptoms such as numbness or tingling in the legs.
Obesity – most adults experience difficulties in maintaining a healthy weight
for their height.
Crowded teeth – the upper jaw is typically small, which causes the teeth to
overcrowd.
Higher risk pregnancies – pregnant women with achondroplasia need expert
antenatal care. Caesarean section is the usual mode of delivery.
Treatment for dwarfism
There is no cure for achondroplasia. Human growth hormone has no place in its
management, as the condition is not caused by a lack of growth hormone.
Treatment focuses on the prevention, management and treatment of medical
complications as well as social and family support.
surgery – may be advised to relieve pressure on the nervous system, generally
at the base of the skull and lower back, or to open obstructed airways by
removing the adenoids
dental and orthodontic work – to correct malocclusion and ensure dental health
support from other health care providers – including geneticists, neurologists
and paediatricians.
Where to get help
Victorian Clinical Genetics Services (VCGS), Southern Cross Bone Dysplasia
Centre (Director, Dr Ravi Savarirayan) Tel. (03) 8341 6201 (for appointments)
Short Statured People of Australia (Victorian branch) Tel. (03) 9560 6895
Your local doctor (can refer you to VCGS bone dysplasia clinics).
Things to remember
Dwarfism is a disorder characterised by shorter than normal skeletal growth
that can be genetic.
Achondroplasia is a common form of short-limbed dwarfism.
The majority of children born with the disorder have average-sized parents.