Restricted growth, sometimes known as dwarfism, is a condition characterised by short stature.
There are two main types of restricted growth:
- proportionate short stature (PSS) – a general lack of growth, where the length of the trunk and limbs are in proportion
- disproportionate short stature (DSS) – where the limbs are shorter or out of proportion with other parts of the body
As well as having short stature, some people with restricted growth also have other physical problems, such as bowed legs or an unusually curved spine.
However, most people don’t have any other serious problems. They can often live a relatively normal life and have a normal life expectancy.
Read more about the symptoms of restricted growth.
What causes restricted growth?
The most common cause of PSS is being born to small parents, but it can sometimes occur as a result of the body not producing enough growth hormone.
DSS usually occurs as part of a genetic condition, such as achondroplasia. Many children born with DSS have parents of average height and the faulty gene causing the condition occurred by chance.
If your child is diagnosed with restricted growth, tests will be carried out to try to identify the underlying cause.
Managing restricted growth
Treatments recommended for people with restricted growth depend on the cause of the condition and any associated problems they have. A number of different healthcare professionals will usually be involved in your care.
Some people with restricted growth may benefit from treatment with growth hormone injections, which can help a child with restricted growth grow more than they otherwise would.
In cases of DSS where the legs are particularly short, a leg-lengthening procedure is sometimes used, although this is controversial and there is uncertainty about its safety and effectiveness.
Read more about treatments for restricted growth.
Symptoms of restricted growth
People with restricted growth (dwarfism) often have no symptoms other than short stature, although some people have associated health problems.
Symptoms commonly seen in people with proportionate and disproportionate short stature are outlined below.
Proportionate short stature
People with proportionate short stature (PSS) grow very slowly and have a general lack of growth throughout the body. The length of the trunk (tummy and chest) remains in normal proportion with the legs.
PSS may not be noticeable until later in childhood or until a child reaches puberty.
Additional symptoms associated with PSS depend on the underlying cause. For example:
- people with growth hormone deficiency may have low energy levels, increased body fat, weak bones (osteoporosis), dry skin, reduced muscle strength and high cholesterol
- girls and women with Turner syndrome won’t start having periods and won’t be able to have children
- people with Prader-Willi syndrome may have a constant desire to eat, reduced muscle tone (hypotonia), learning difficulties and behavioural problems
- people with chronic illnesses affecting organs such as lungs, heart or kidneys will have further symptoms relating to their underlying condition
Read more about the causes of restricted growth.
Disproportionate short stature
In people with disproportionate short stature (DSS), there is an overall lack of growth, and certain limbs may be shorter or out of proportion with other parts of the body.
People with achondroplasia, one of the most common causes of DSS, typically have:
- a normal-length trunk with short arms and legs
- a large head with a prominent forehead and flat nasal bridge
- short and wide hands and feet
- short fingers and toes
Most people with DSS don’t have any other significant health problems, although some people with achondroplasia have:
- bowed legs, which may cause ankle or knee pain
- abnormal curvature in the top of the spine (kyphosis) and/or sideways curvature of the spine (scoliosis)
- a build-up of fluid around the brain (hydrocephalus)
- repeated middle ear infections, which can cause hearing difficulties
- irregular breathing at night (sleep apnoea), which can interrupt sleep and cause excessive sleepiness during the day
- numbness and weakness in the legs, caused by the compression of the spinal cord and nerves leaving the spine
Causes of restricted growth
Restricted growth (dwarfism) may be caused by many different medical conditions, and is more noticeable in some conditions than others.
Causes of proportionate short stature
The main cause of proportionate short stature (PSS) is being born to small parents.
A less common cause is the body not producing enough growth hormone, which is estimated to affect one in every 3,500 to 4,000 children.
This may be present at birth, because of problems with the pituitary gland (a pea-sized gland below the brain responsible for producing several important hormones) or as part of another condition. It can also start in childhood, as the result of an injury, a brain tumour or radiotherapy to the brain.
In about half of children with growth hormone deficiency, the cause is unknown.
Other possible causes of PSS include:
- long-term conditions – such as those affecting the lungs, heart or kidneys
- steroid treatment for a chronic condition – such as asthma
- genetic abnormalities – such as Down’s syndrome, Noonan syndrome, Turner syndrome, Prader-Willi syndrome and short stature homeobox-containing gene (SHOX) deficiency
- malnutrition or poor absorption of food – for example, in coeliac disease
If your child is diagnosed with restricted growth, tests may be carried out to try to identify the underlying cause.
Read more about diagnosing restricted growth.
Causes of disproportionate short stature
Conditions associated with disproportionate short stature (DSS) are usually caused by a faulty gene. The affected genes stop the bones and cartilage developing properly, leading to restricted growth that is often noticeable from birth.
Many children born with DSS have parents of average height and the change to the gene happens by chance. However, people with conditions that cause DSS may pass their condition on to their children.
The most common cause of DSS is a condition called achondroplasia, which is estimated to affect around one in every 25,000 people.
Other conditions that cause DSS include:
- mucopolysaccharide disease
- diastrophic dysplasia
- spondyloepiphyseal dysplasia
- multiple epiphyseal dysplasia
- Conradi syndrome
- Ellis-van Creveld syndrome
You can read more about some of these rare conditions on the Restricted Growth Association website.
Diagnosing restricted growth
A diagnosis of restricted growth (dwarfism) is based on symptoms, height measurements, family history and tests.
Depending on the cause of the condition, restricted growth may be diagnosed before or soon after a child is born, or when growth problems become more obvious as they get older.
Tests may not need to be carried out if you or your child don’t have any other health problems.
Diagnosing growth hormone deficiency
Growth hormone deficiency is usually diagnosed using growth hormone stimulation tests.
Medicine is injected into a vein to cause growth hormone levels in the blood to increase. If the level of growth hormone is found to be lower than normal, it indicates growth hormone deficiency.
A scan of the brain is necessary to look at the pituitary gland (which produces growth hormone) if blood tests show low levels of growth hormone.
Diagnosing conditions that cause restricted growth
The following tests can be used to diagnose a condition that causes short stature:
- blood tests to check for any liver, kidney and bone problems or malnutrition – blood tests can also be used to analyse chromosomes, which can help to diagnose some genetic conditions, such as Turner syndrome
- urine tests to confirm some enzyme deficiency disorders – such as mucopolysaccharide disease
- imaging tests such as X-rays or MRI scans to check for abnormalities in the bones or pituitary gland – which may indicate growth hormone deficiency
Diagnosis in pregnancy
Diagnosis during pregnancy (also called prenatal diagnosis) may be offered to parents who have a genetic history of a condition that causes short stature.
Some potential abnormalities may be visible during routine ultrasound scans, but tests such as chorionic villus sampling or amniocentesis are needed to confirm a diagnosis, as they can be used to see if your baby carries one of the faulty genes associated with restricted growth.