Dwarfism

Introduction

Restricted growth is a symptom of many different medical conditions. It is more noticeable in some conditions than others.

Restricted growth is usually categorised as either:

• proportionate short stature (PSS), or
• disproportionate short stature (DSS).

Proportionate short stature

PSS means there is general lack of growth throughout the body. The length of the trunk (abdomen and chest) remains in normal proportion with the legs. Adults rarely reach five feet tall.

The most common cause of PSS is being born to small parents. PSS can also happen when the body does not produce enough growth hormone, or cannot process it properly (see Causes page).

In some cases, hormone treatment can be used to treat people with proportionate short stature (see Treatment page).

Disproportionate short stature

DSS occurs when there is a problem with the way joints and bones grow. Certain limbs may be shorter, or there might be a severe lack of general, all-over body growth (see Symptoms page). Adults are usually between 107cm (3ft 6in) and 137cm (4ft 6in) in height.

Conditions associated with DSS are usually caused by genetic mutation (change in the genes). Many children born with DSS will have average-height parents and the genetic mutation will have occurred spontaneously.

Treatment will depend upon the cause of the short stature and is likely to involve a multidisciplinary approach (seeing many different types of healthcare professionals).

If the legs are particularly short, DSS can be treated with a leg-lengthening procedure (see Treatment page), although there is uncertainty about the safety and effectiveness of this.

Genetic

Genetic is a term that refers to genes. Genes are the characteristics inherited from a family member.

Genes

Genes contain information that you inherit from your parents, such as eye or hair colour. They are carried by chromosomes.

 

Symptoms

Proportionate short stature

People with proportionate short stature, including girls with Turner syndrome, grow very slowly but their body parts are in proportion. Without treatment, they rarely reach five feet tall.

Adults with a growth hormone deficiency are at greater risk of osteoporosis (thin, weak bones) and cardiovascular disease. They have reduced muscle strength and have a lower capacity for exercise.

Disproportionate short stature

Adults with disproportionate short stature (DSS) are usually between 107cm (3ft 6in) and 137cm (4ft 6in) in height, and they may also have one or more of the following features or symptoms:

• Bowed legs.
• Scoliosis, which is the spine curving to one side.
• Kyphosis, which is the upper spine curving outwards.
• Spinal stenosis, which is the spinal canal (though which the spinal cord passes) becoming narrower than normal.
• Back problems. In certain conditions, spinal problems (above) 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, making it hard to balance.
• Sleep apnoea, which is a sleep disorder that causes irregular breathing at night and excessive sleepiness during the day.
• Hearing difficulties. Young children may experience these and have 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 the bones in the neck, which must be identified and treated early.
• Hydrocephalus, which is too much fluid in the brain cavities.

 

Causes

Proportionate short stature

Growth hormone deficiency

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.

Growth hormone deficiency can start in adulthood or childhood:

• Adult-onset growth hormone deficiency is commonly caused by tumours of the pituitary gland (pea-sized gland below the brain), or by radiation therapy to the head.
• Child-onset growth hormone deficiency may be present from birth, due to problems with the pituitary gland or as part of another syndrome. It may also occur after birth as a result of injury or disease affecting the head. In some cases, no cause can be found.

Other causes

Other possible causes of PSS are:

• Turner syndrome – where defects in chromosomes can cause restricted growth in girls (see Useful links),
• chronic illnesses, such as those affecting the lungs, heart or kidneys, or
• treatment for a chronic illness (for example, arthritis), which may slow the release of growth hormone in your body.

Disproportionate short stature

Conditions associated with disproportionate short stature (DSS) are usually caused by genetic mutation (change in the genes). Many children born with DSS will have average-height parents and the genetic mutation will have occurred spontaneously. The affected genes stop the bones and cartilage developing properly, leading to restricted growth.

People with conditions causing DSS may pass their condition on to their children. Conditions causing DSS are usually present from birth (congenital).

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 causing DSS include:

• hypochondroplasia,
• mucopolysaccharide disease,
• diastrophic dysplasia,
• spondyloepiphyseal dysplasia (SED),
• multiple epiphyseal dysplasia,
• pseudochondroplasia,
• Conradi syndrome, and
• Ellis-van Creveld syndrome.

For information on any of these rare conditions, go to the UK’s Restricted Growth Association website

 

Diagnosis

Diagnosis of restricted growth is based on symptoms, measurement of height, family history and tests (see below).

Proportionate short stature may not be noticeable until childhood or adolescence, when growth patterns start to show a delay.

Diagnosing growth hormone deficiency

A diagnosis of growth hormone deficiency is usually confirmed using an insulin tolerance test (ITT), where insulin is injected into a patient’s vein to cause their blood sugar level to fall.

An ITT tests the function of the pituitary gland when the blood sugar level is low. A fully-functioning pituitary gland would release growth hormone when the blood sugar level falls. If the pituitary gland is not working properly, growth hormone levels would be lower than normal, indicating growth hormone deficiency. 

Diagnosing the underlying condition

The conditions that cause disproportionate short stature are often diagnosed at birth, but may be diagnosed later than this in some cases (for example, pseudochondroplasia is often diagnosed at around three years of age).

Generally, the following tests are used to diagnose an underlying condition causing short stature:

• Blood tests to analyse chromosomes are used to diagnose some conditions.
• Urine tests can confirm some enzyme deficiency disorders (such as mucopolysaccharide disease).
• X-rays and biopsies of bone marrow or skin can help to diagnose abnormalities that indicate certain conditions.

Treating Restricted Growth

Treatment will depend upon the cause of the short stature and is likely to involve a multidisciplinary approach (seeing many different types of health professionals).

Proportionate short stature

Hormone treatment for children

Human growth hormone can help stimulate growth in children with a growth hormone deficiency.

In 2002, the UK’s National Institute for Health and Clinical Excellence (NICE) recommended somatropin (human growth hormone treatment) for children with a proven diagnosis of growth hormone deficiency.

For example, somatropin is given to girls with Turner syndrome as soon it becomes obvious they are not growing normally, sometimes when they are as young as one or two. This helps to prevent short stature during adulthood.

Somatropin is usually given daily, by injection, as a single dose. It can increase height by as much as 10cm.

For more information, read the NICE guidelines on Growth hormone deficiency in children

Hormone treatment for adults

Human growth hormone helps treat the symptoms of growth hormone deficiency in adults.

Replacing levels of human growth hormone appears to lower the risk of cardiovascular disease and increase bone mineral density in adults with a growth hormone deficiency, lowering their risk of bone fractures.

In 2003, the NICE recommended human growth hormone treatment (somatropin) for adults with growth hormone deficiency if they fulfilled the following criteria:

• they have severe growth hormone deficiency (determined after an insulin tolerance test or equivalent test),
• they have a perceived impaired quality of life (determined using a special questionnaire), and
• they are already receiving treatment for another pituitary hormone deficiency.

Somatropin is self-administered by a daily injection.

Side effects may include headache, joint pain, muscle pain, fluid retention, visual problems and nausea or vomiting.

The NICE guidelines state: ‘…Based on the evidence from randomised controlled trials, in terms of quality of life the effectiveness of growth hormone treatment in adults with growth hormone deficiency remains unproven.’

For more information, read the NICE guidelines on Growth hormone deficiency in adults

Controlling long-term conditions

Controlling chronic (long-term) conditions such as lung disease, heart disease or arthritis from an early stage can lessen the effect of these on growth.

Disproportionate short stature

Treatments should focus on preventing or treating any complications that may occur in the condition that causes disproportionate short stature (DSS).

Children should attend for regular check-ups with their health team and be referred on to a paediatric (child) specialist at the earliest opportunity. Their care is likely to involve a team of healthcare professionals which may include one or more of the following:

• physiotherapists,
• occupational therapists,
• audiologists (hearing specialists),
• speech and language therapists,
• neurologists (specialising in disorders of the nervous system),
• orthopaedic specialists (specialising in spine and joint problems), and
• geneticists.

Leg lengthening

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, which is gradually adjusted every day to lengthen the bone.

However, this can be a long procedure and is not without the risk of complications. Also, it may not always achieve the desired results. Given that there is uncertainty about the safety and effectiveness of distraction in lengthening the leg bone, it is important that you understand exactly what the procedure entails and talk to your doctor about the risks.

Some people experience pain after the limb lengthening procedure. Other potential complications include:

• poor bone formation,
• infection,
• bone lengthening at an inappropriate rate, and
• deep vein thrombosis (a blood clot in a vein).

For more information, read the NICE 2006 guidelines on Intramedullary Distraction for Lower Limb Lengthening or the NHS leaflet on IlizarovFixation for Limb Lengthening

https://www.hse.ie/eng/health/az/d/dwarfism/ [1]