Restricted growth (dwarfism) is a condition characterised by short stature. It can be caused by several different medical conditions.
There are two main types of restricted growth:
- proportionate short stature (PSS) – a general lack of growth
- disproportionate short stature (DSS) – a problem with the way certain bones grow
Read more about the symptoms of restricted growth.
Proportionate short stature (PSS)
If someone has PSS, the length of their trunk (abdomen and chest) will be in normal proportion with the legs, but they will have a general lack of height.
The most common cause of PSS is being born to small parents. PSS can also occur when the body does not produce enough growth hormone.
Certain genetic syndromes may also cause PSS. For example, girls with Turner syndrome and children with a genetic abnormality known as SHOX gene haploinsufficiency have a mild form of PSS.
Read more about the causes of restricted growth.
Disproportionate short stature (DSS)
DSS occurs when there is a problem with the way joints and bones grow. Certain limbs may be shorter, or the trunk may be particularly short. Generally, there may be a severe lack of height.
Conditions associated with DSS are usually caused by a faulty gene. Many children born with DSS have parents of average height and the faulty gene occurred by chance.
Treatment will depend on the cause of short stature and is likely to involve many different types of healthcare professionals.
If the legs are particularly short, DSS can be treated with a leg-lengthening procedure, although there is uncertainty about the safety and effectiveness of this.
Some children with restricted growth may be eligible for treatment with human growth hormone.
Find out more about treating restricted growth.
People with restricted growth (dwarfism) will probably have other symptoms associated with the health condition responsible for their short stature.
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 but their body parts are in proportion.
Disproportionate short stature
People with disproportionate short stature (DSS) may also have one or more of the following features or symptoms:
- Bowed legs.
- Scoliosis – the spine curves to one side.
- Kyphosis – the upper spine curves outwards.
- Back problems – in certain conditions, these spinal problems may lead to compression of the spinal cord and nerves leaving the spine. This causes pain and numbness in the hips, knees and legs, and can make it difficult to move around.
- Top-heavy head in comparison to the rest of the body – this makes it hard to balance.
- Sleep apnoea – this sleep disorder causes irregular breathing at night and excessive sleepiness during the day.
- Hearing difficulties – young children may have hearing difficulties and problems with speech and language.
- Osteoarthritis – this type of arthritis particularly affects the hip and knee joints in DSS. If other joints are also affected, it may be very difficult to move around. In some conditions, the joints cannot be fully straightened.
- Weakness in the neck – in certain conditions, there may be weakness of the joints between bones in the neck, which must be identified and treated early.
- Hydrocephalus – this is excess fluid in the brain cavities.
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. The growth hormone deficiency may be present at birth, due to problems with the pituitary gland (a pea-sized gland below the brain responsible for producing several important hormones) or as part of another condition. Or it may start in childhood, as the result of an injury or disease affecting the head.
In about half of children with growth hormone deficiency, the cause is unknown. Growth hormone deficiency is estimated to occur in 1 in 3,500-4,000 children.
Other possible causes
Other possible causes of PSS include:
- chronic illnesses, such as those affecting the lungs, heart or kidneys
- steroid treatment for a chronic illness, such as arthritis
- genetic abnormalities such as Down's syndrome, Noonan syndrome, Turner syndrome and Prader-Willi syndrome
- malnutrition or poor absorption of food (for example, in coeliac disease)
Disproportionate short stature
Conditions associated with disproportionate short stature (DSS) are usually caused by a faulty gene. Many children born with DSS have parents of average height and the change to the gene happens by chance. The affected genes stop the bones and cartilage developing properly, leading to restricted growth.
People with conditions that cause DSS may pass their condition on to their children. Conditions that cause DSS are usually present from birth.
The most common cause of DSS is a condition called achondroplasia. This causes shortened limbs (especially the upper arms and thighs), a large skull with prominent forehead, short hands and feet, and spinal abnormalities.
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 information on any of these rare conditions on the Restricted Growth Association website.
A diagnosis of restricted growth (dwarfism) is based on symptoms, measurement of height, family history and tests.
Proportionate short stature may not be noticeable until childhood or adolescence.
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 pituitary gland is not working properly, growth hormone levels will be lower than normal, indicating growth hormone deficiency.
Two growth hormone stimulation tests are usually required to diagnose growth hormone deficiency. A scan of the brain is necessary to look at the pituitary gland if blood tests show low levels of growth hormone being produced.
Diagnosing a condition that causes restricted growth
Conditions that cause disproportionate short stature are often diagnosed at birth. However, in some cases they may be diagnosed later. For example, pseudoachondroplasia is often diagnosed at around three years of age.
Generally, the following tests are used to diagnose a condition that causes short stature:
- Blood tests - to check for evidence of any liver, kidney and bone problems or malnutrition. Blood tests can also be used to analyse chromosomes, which can help to diagnose some conditions, such as Turner syndrome.
- Urine tests can confirm some enzyme deficiency disorders, such as mucopolysaccharide disease.
- Imaging tests such as Xrays or MRI scans check for abnormalities in the bones or pituitary gland, which may indicate growth hormone deficiency
- Biopsies of bone marrow or skin can help diagnose abnormalities that indicate certain conditions.
Human growth hormone can help stimulate growth in children with growth hormone deficiency.
This and other available treatments for short stature are outlined below.
Growth hormone treatment
The following may be options for children whose growth failure is associated with any of the following conditions:
- growth hormone deficiency
- Turner syndrome
- Prader-Willi syndrome
- chronic kidney disease
- children who are born small and fail to catch up in growth by the age of four or later
- children with a particular faulty gene, known as short stature homeobox-containing gene deficiency (or SHOX gene haploinsufficiency)
Children with true growth hormone deficiency respond very well to growth hormone treatment. Growth response in children with other conditions can vary, and treatment may be started at different ages depending on the growth pattern of the child.
For example, growth hormone is given to girls with Turner syndrome as soon as it becomes obvious that they are not growing normally. This may help to improve their adult height.
Somatropin treatment should always be started and monitored by a child health specialist (paediatric endocrinologist) with expertise in managing growth hormone disorders in children. It is usually given as a single daily dose by injection.
Skin reactions are the most commonly reported side effect of somatropin. In very rare cases, the treatment is associated with persistent severe headaches, vomiting and vision problems.
Controlling long-term conditions
Controlling long-term conditions, such as lung disease, heart disease, bowel disease or arthritis, from an early stage can reduce the effect these conditions have on growth.
Children should have regular check-ups with their health team and should be referred to a child health specialist (paediatrician) as early as possible. Their care is likely to involve a team of healthcare professionals, including one or more of the following:
- occupational therapists
- hearing specialists (audiologists)
- speech and language therapists
- specialists in nervous system disorders (neurologists)
- specialists in spine and joint problems (orthopaedic specialists)
- children's nurse specialists
If a person has particularly short legs, a leg-lengthening process, known as distraction, is an option. This involves breaking the leg bone and fixing it to a special frame. This is gradually adjusted every day to lengthen the bone.
However, this can be a long procedure and has a risk of complications. Also, it may not always have the desired results. As there is uncertainty about the safety and effectiveness of distraction in lengthening the leg bone, it is important to understand exactly what the procedure involves and to talk to your orthopaedic specialist doctor about the risks.
Some people have pain after the limb-lengthening procedure. Other possible complications include:
- poor bone formation
- bone lengthening at an inappropriate rate
- a blood clot in a vein