What Is Short Stature (Dwarfism)? What Causes Short Stature?
Dwarfism, nanism, short stature, or restricted growth is a medical disorder in which the person is of abnormally short stature. According to various sources, short stature may be caused by over 200 different medical conditions. According to the LPA (Little People of America), dwarfism is defined as an adult height of 4 feet 10 inches (148 cm) or less. However, as population groups around the world have varying average statures, height definition may vary. Today the term short stature is becoming more widely used, while the term dwarfism is becoming obsolete.
The height of people with short stature may vary from about 81 cm (2 feet 8 inches) to 142 cm (4 feet 8 inches).
According to The Mayo Clinic, USA, current treatments for short-stature-related conditions are aimed at lessening complications, rather than increasing height.
Throughout history, and also today, people with short stature may experience discrimination. People with short-stature are more likely to address educational, occupational and social challenges with good family support, social networks, advocacy groups and adaptive products.
According to the National Health Service (NHS), UK, restricted growth is categorized as either:
- PSS (proportionate short stature) - there is less-than-normal general growth throughout the body. The trunks of adults are in proportion to their legs (trunk = abdomen and chest). Typically, a person with PSS is shorter than 5 feet tall. The most common reason is having short parents. PSS may also occur if the person's body either does not process growth hormone properly, or does not produce enough of it. There are about 12,600 adults with growth hormone deficiency in England and Wales (Source: NHS). Growth hormone treatment is sometimes an effective treatment for people with PSS.
- DSS (disproportionate short stature) - this occurs when the joints and bones do not grow properly. The person may have a severe lack of all-over body growth, or some limbs may be shorter in proportion to the rest of their body.
DSS is generally linked to a change in the genes (genetic mutation). A significant proportion of children with DSS have parents who are not below average height. Experts say the genetic mutation must have occurred spontaneously (rather than inheriting a genetic fault).
According to the NHS, there are about 30,000 people with restricted growth conditions that cause DSS in the UK.
DSS treatment usually involves a multidisciplinary approach - the patient sees a wide range of health care professionals. A leg-lengthening procedure may be used for people with short legs. However, there are doubts about the procedures safety and efficacy.
Dwarfism is an "Obsolete term for a condition or a group of conditions in which the height of the person while standing is below the third percentile. Usually termed short stature."
Short stature in pediatrics is "..height below the third percentile when plotted on a growth chart."
In the rest of this article the terms short stature and restricted growth will be used, rather than the (obsolete) term dwarfism.
What are the signs and symptoms of short stature?
A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor notice. For example, pain may be a symptom while a rash may be a sign.Short stature may be caused by one of over 200 different medical conditions, or a combination of them. Therefore, signs, symptoms and features vary considerably. In general, the disorders are divided into two main categories - PSS (proportionate short stature) and DSS (disproportionate short stature).
PSS (Proportionate short stature)
The individual grows very slowly. However, all the body parts grow in the right proportions to each other (limbs are not too long or short in relation to the rest of the body). Without treatment, a child with PSS does not generally reach an adult height of five feet or over.
An adult with a growth hormone deficiency is more susceptible to developing osteoporosis, having cardiovascular problems, and reduced muscle strength. All three combined mean there is a lower capacity for physical exercise.
PSS usually results from a medical condition or disorder which is present either at birth, or during early childhood. The condition limits growth and development. Most of the disorders are rare, so signs and symptoms may vary considerably. As the disorder affects overall growth, often there is poor development in at least one body system. Some very rare disorders may result in cognitive problems (mental developmental problems).
Growth hormone deficiency occurs when the pituitary gland does not produce enough growth hormone. Growth hormone is essential for normal childhood growth. Signs and symptoms of growth hormone deficiency include:
- The child's height is below the third percentile of standard pediatric growth charts
- The child's growth rate is slower than other children's of the same age
- Delayed sexual development during teen years
- No sexual development during teen years
- A wide neck (web-like)
- A small lower jaw (receding lower jaw)
- A high and narrow palate
- The hairline at the back of the head is low
- Widely spaced nipples
- Broad chest
- Short hands
- Cubitus valgus - the arms turn outward at the elbows
- Arms and feet swell, especially at birth
- Delayed growth
- Delayed sexual development
An adult with DSS will have a height between 81 cm (2 feet 8 inches) and 142 cm (4 feet 8 inches). These measurements can vary, e.g. the NHS (UK) describes a stature range from 107cm (3 foot 6 inches) to 137cm (4 feet 6 inches).
Most individuals with DSS have an average-sized trunk and very short limbs. However, some may have a very short trunk and shortened, but disproportionately large limbs. A disproportionately large head size is a common characteristic of DSS.
The majority of people with DSS have variations of intelligence similar to the rest of the population. Cognitive abilities may sometimes be affected if there is too much fluid around the brain (hydrocephalus).
The following signs, symptoms or features may also be present in people with DSS:
- Bowed legs
- The spine curves to one side (scoliosis)
- The upper spine curves outwards (kyphosis)
- The spinal canal may be narrower than normal (spinal stenosis)
- Pain and numbness - compression of the spinal cord and nerves may result in pain and numbness in the knees, legs, and hips. Sometimes mobility is affected.
- Top-heavy head - this may result in balance problems, because the head is proportionally larger (compared to the rest of the body), giving the individual a higher center of gravity.
- Sleep apnea - a breathing disorder that occurs during sleep; the patient breathes irregularly. Sleep apnea often results in fatigue and sleepiness during the waking hours.
- Hearing problems - may occur more commonly in children. Speech and language development may be affected.
- Osteoarthritis - a type of arthritis which targets the hip and knee joints in people with DSS. Patients whose other joints are also affected may have mobility problems. In some more severe cases the joint(s) does not straighten out completely.
- Neck weakness - the joints in the bones in the neck may be weak. If identified early on the condition is treatable.
- Too much liquid in the brain cavities (hydrocephalus)
Achondroplasia is caused by a mutation in FGFR3 (the fibroblast growth factor receptor-3 gene). FGFR3 is located on chromosome 4 in chromosome band 4p16.3. People with achondroplasia may have the following signs, symptoms and features:
- Average sized trunk
- Short limbs. The upper arms and upper legs are particularly short.
- Short fingers. There may be a wide separation between the middle and ring fingers.
- Elbows have limited mobility.
- Large head, with prominent forehead, and flattened bridge of the nose.
- Progressive genu varum - bowed legs
- Lordosis - progressive development of swayed lower back
- Average adult height of 4 feet (122 cm)
- Very short trunk. During infancy this may not be noticeable.
- Short neck.
- Short limbs.
- Hands and feet of average size
- Flattened cheekbones
- Coxa vara - a hip deformity, resulting in inward-turning thighbones
- Clubfoot - twisted feet, or feet that are out of shape
- Kyphosis - curvature of the upper spine (progressive)
- Progressive development of lordosis (swayed lower back)
- Hearing problems
- Vision problems
- Adult height from 91cm (3 feet) to 122cm (4 feet)
What are the causes of short stature?
Causes of PSS (proportionate short stature)The most common cause of PSS is having short/small parents. A growth hormone deficiency is also a cause (less common).
The onset of growth hormone deficiency can occur during infancy or adulthood:
Adult-onset growth hormone deficiency - in such cases, the causes may be a tumor in the pituitary gland, or radiotherapy (radiation therapy) to the patient's head.
Child-onset growth hormone deficiency - this is often present at birth. Also, it is a problem with the pituitary gland. Sometimes it may be part of another syndrome. Injuries or diseases that affect the head are the main causes when onset is during childhood, but after birth.
PPS may also be caused by:
- Turner syndrome (girls)
- Some chronic (long-term or recurring) illnesses, especially of the lungs, heart or kidneys are affected.
- Chronic illness treatment. E.g. arthritis treatment may affect the proper release of growth hormone in the body.
In the majority of cases, conditions linked to DSS are caused by a change in the genes - a genetic mutation. As a significant number of children born with DSS have parents of average stature, experts say that the genetic mutation occurred spontaneously, rather than as a result of an inherited genetic trait. The genetic mutation affects the development of bone and cartilage, which undermines physical growth.
A parent who has a condition linked to DSS may pass that condition on to their children. The following conditions are linked to DSS:
- Achondroplasia (most common cause of DSS)
- Conradi syndrome
- Diastrophic dysplasia
- Ellis-van Creveld syndrome
- Hypochondroplasia
- Mucopolysaccharide disease
- Multiple epiphyseal dysplasia
- Pseudochondroplasia
- Spondyloepiphyseal dysplasia (SED)
Diagnosis of short stature
In order to diagnose restricted growth, the doctor will look at the signs, ask the patient (or parents, caregivers) about symptoms, check their medical and family histories, and possibly carry out some tests. Individuals with PSS (proportionate short stature) may not show signs and symptoms until later on during childhood or adolescence.A pediatrician will examine a number of factors and characteristics to monitor and asses a child's growth to determine whether they have a short stature disorder. In some cases a pediatrician may refer the patient to other specialists, such as an orthopedic pediatrician (specializes in bone abnormalities), an endocrinologist (hormone specialist), or a doctor who specializes in genetics.
Diagnosis of growth hormone deficiency - the doctor will order an ITT (insulin tolerance test). Insulin is injected into a vein, causing blood glucose levels to drop. In a healthy individual, a drop in blood glucose (sugar) levels will trigger the pituitary gland to release growth hormone. If growth hormone levels are lower than normal, it usually means there is a growth hormone deficiency.
The child's measurements - a baby will have his/her height, weight and head circumference measured at specific intervals. After each visit, the pediatrician plots the data on a chart, which indicates the percentile ranking for each measurement, as well as expected growth in the future. With the aid of the chart, which is specific to the child, a doctor can identify any growth abnormality. If some of the measurements do not follow normal patterns, the doctor may ask for more regular visits.
The child's appearance - during each visit the doctor will be aware of, and look out for, distinct facial and skeletal features linked with conditions that are associated with short stature. The child's appearance may help the doctor make a diagnosis.
Diagnosing underlying conditions
Most conditions linked to DSS (disproportionate short stature) are diagnosed when the baby is born. However, sometimes diagnosis may occur later on. The following tests may be used to diagnose an underlying condition linked to DSS:
- Blood tests - chromosome analyses may diagnose some conditions. However, genetic tests are often not needed to make an accurate diagnosis. A test may be ordered simply to distinguish among possible diagnoses when other evidence is not clear. A child (girl) who is thought to have Turner syndrome may undergo special laboratory tests to assess the state of X chromosomes - this can be done via a blood test.
- Family history - the pediatrician may wish to list the stature of the patient's siblings, parents, grandparents and other relatives. The aim here is to work out the average height of family members and determine whether short stature is a family trait.
- Urine tests - to check for enzyme deficiency disorders.
- Imaging technology tests/scans - the doctor may order X-rays, because some abnormalities of the skeleton and skull may show up and help the physician identify a disorder. An MRI (magnetic resonance imaging) scan can show up problems with the pituitary gland or hypothalamus, which have a role to play in hormone function.
- Bone marrow or skin biopsies - these may be useful for confirming conditions associated with short stature.
What are the treatment options for short stature?
The type of treatment an individual receives depends on what has caused the short stature. Most likely, various different healthcare professionals from different areas of medicine will be involved - a multidisciplinary treatment approach.PSS (proportionate short stature) treatment
Pediatric hormone treatment (for children) - human growth hormone may help children who have a deficiency, i.e. the treatment may stimulate physical growth. In 2002 NICE (National Institute for Clinical Excellence), UK, recommended somatropin for children who are diagnosed with a growth hormone deficiency. Somatropin can help prevent short stature later on in life if treatment starts early enough. Treatment involves a daily injection. The patient may gain as much as 10cm in eventual height.
Adult hormone treatment - when treatment is given to adults the focus is on protecting from, for example, cardiovascular disease and low bone mineral density. In the UK somatropin is prescribed for adults with growth hormone deficiency as long as:
- The growth hormone deficiency is severe
- The patient's quality of life is seen to be impaired
- The patient is already receiving treatment for another pituitary hormone deficiency
Somatropin side effects may include headache, muscle pain, edema (fluid retention), problems with eyesight, joint pain, vomiting and nausea.
NICE's guidelines stress that growth hormone treatment effectiveness in adults remains unproven, according to randomized clinical trials carried out so far.
According to the Society for Endocrinology (UK), about 1,750 adults in the United Kingdom receive growth hormone deficiency treatment.
Long-term (chronic) conditions
If such chronic conditions as heart disease, lung disease and arthritis can be controlled early on, the detrimental effects on growth are significantly lower.
Treatment for DSS (Disproportionate short stature)
Treatment for patients with DSS focuses on the complication(s) that are linked to DSS. Any child with DSS should regularly have check-ups and be referred to a pediatrician as soon as possible. Treatment will probably involve a substantial team of health care professionals, including:
- Audiologists
- Geneticists
- Neurologists
- Occupational therapists
- Orthopedic specialists
- Physical therapists (physiotherapists)
- Speech and language therapists
Results may be good. However, it is a long process with risks of complications. Also, it might not work. It is important for the patient and family to fully understand what is entailed in the procedure and what the most likely outcome might be.
Leg lengthening includes the following potential complications:
- Pain; even after the procedure
- Bone formation is poor
- Infection
- Bone lengthens at an inappropriate rate
- DVT (deep vein thrombosis) - a blood clot in a vein
Growth plates - metal staples are inserted into the ends of long bones where growth takes place. The aim is to help bones grow in the right direction.
Inserting staples or rods in order to help the spine get into the right shape.
Increasing the size of the opening in bones of the spine to reduce pressure on the spinal cord.
Complications
DSS (disproportionate short stature) complications- Arthritis later in life
- Delayed mobility development, e.g. crawling, walking and sitting up.
- Dental problems
- Genu varum (bowing of legs)
- Hearing problems
- Hydrocephalus (too much fluid in the brain cavities)
- Kyphosis (hunching of the back)
- Limb problems
- Lordosis (swaying of the back)
- Lumbosacral spinal stenosis (narrowing of the channel in the lower spine during adulthood)
- Otitis media (occurring more frequently)
- Sleep apnea
- Spine problems
- Weight gain
Poorly developed organs, caused by disorders associated with PSS.
Pregnancy complications
A woman with short stature who is pregnant has a higher risk of developing respiratory problems. C-sections (cesarean section) are almost always required.
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