Dwarfism

Dwarfism (or conditions of short stature) refers to a group of conditions characterized by shorter than normal skeletal growth. This shortness can show in the arms and legs or in the trunk. There are over 100 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 information on this page focuses on achondroplasia, but much of it may also apply to other conditions.

Most children born with achondroplasia have average-sized parents. Children with achondroplasia may be slower to develop motor skills, such as controlling the movements of the head, but their intellectual development is normal. The average final height for a person with achondroplasia is around 130 cm for men and 125 cm for women.

Short-statured people lead normal, fulfilled lives. Achieving higher levels of education, as well as career and personal ambitions, is not limited by stature.

Symptoms of dwarfism#

The characteristics of achondroplasia can 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 flattened bridge of the nose and a flat mid-face
• a prominent forehead
• crowded teeth, because of a small upper jaw

Skeletal dysplasias and dwarfism#

Dysplasia means ‘abnormal growth’. There are around 100 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 the genetic mutation that causes achondroplasia occurs during conception, when the mother’s egg is fertilized by the father’s sperm. It is not known why this mutation occurs, or how it translates into the characteristics of achondroplasia.

The remaining 20 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, their child has a one in four risk of inheriting the faulty gene from both parents. This causes a fatal condition known as ‘double dominant’ or homozygous achondroplasia, and children born with this variation generally do not live beyond 12 months of age. The same child has a 50 per cent chance of inheriting one copy of the gene (and therefore having achondroplasia), and a one in four chance of not inheriting the gene at all (and having average stature).

Common problems during infancy and childhood#

Children with achondroplasia may face a number of difficulties, including:

• breathing difficulties – including snoring and sleep apnea (the regular cessation of breathing during sleep), caused by narrowed nasal passages
• ear infections – caused by narrowed Eustachian tubes (the tubes leading from the ears to the throat) and nasal passages
• bowed legs – the legs are initially straight, but over time (in some cases) they become bowed once the child starts walking
• reduced muscle strength – the child has softer muscle tone than usual and needs to be adequately supported until the muscle groups are ready to support the neck and spine
• hydrocephalus – an increased risk (around one in 100) of an accumulation of cerebrospinal fluid inside the skull, which can lead to head enlargement
• narrow foramen magnum – a smaller than normal opening at the base of the skull, where the spinal cord begins; this can sometimes press against the brain stem and cause symptoms including apnea and neurological signs
• increased lumbar lordosis – a backward curve in the lower spine

Common problems during adulthood#

Problems faced by adults with achondroplasia can include:

• nerve compression – the nerves in the lower back (lumbar region) are squashed, which can cause symptoms such as numbness or tingling in the legs
• obesity – most adults have difficulty 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, and cesarean 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. This may include:

• surgery – to relieve pressure on the nervous system (generally at the base of the skull or the lower back), or to open obstructed airways by removing the adenoids
• dental and orthodontic work – to correct malocclusion and ensure dental health
• support from a range of health care providers, including geneticists, neurologists and pediatricians

There are currently preliminary trials of a medication called vosoritide to treat the symptoms of achondroplasia, but these are only in the early stages.

Genetic counseling and dwarfism#

If your child or another family member has been diagnosed with dwarfism, or if dwarfism runs in your family, it can be helpful to speak to a genetic counselor. Genetic counselors are health professionals qualified in both counseling and genetics.

As well as providing emotional support, they can help you understand dwarfism and what causes it, how it is inherited, and what a diagnosis means for your child’s health and development and for your family. They can also explain what genetic testing options are available to you and other family members.

Genetic counselors are trained to provide information and support that is sensitive to your family circumstances, culture and beliefs. You may choose to visit a genetic counselor if you are planning a family – to find out your risk of passing the condition on to your child, or to arrange prenatal tests. Support groups can also connect you with other individuals and families affected by dwarfism.

Key points#

• There are over 100 conditions that cause abnormal skeletal growth and dwarfism.
• Achondroplasia is the most common type, and people with achondroplasia have normal intellectual development and lead full lives.
• Other skeletal dysplasias can cause short-trunk disorders and proportionate short stature.
• Human growth hormone has no place in management, as the condition is not caused by a lack of growth hormone.

Where to get help#