Achondroplasia: Definition, Symptoms and Causes

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Achondroplasia Cause of Dwarfism

DEFINITION

Achondroplasia or commonly known as Dwarfism is short physical stature caused by a medical or genetic condition.

A person is usually considered a dwarf if they are less than 4 ft, 10 in (1.5 m) in height. The average adult with dwarfism is usually about 4 ft (1.2 m) tall.

DESCRIPTION

The term “dwarfism” is often used to describe achondroplasia, a condition characterized by short stature and disproportionately short arms and legs.

This is the most commonly found form of dwarfism. However, there are other, less common forms of dwarfism, as well.Achondroplasia Cause of Dwarfism

In these forms, dwarfs may or may not have disproportionate limbs. In some cases, the individual’s body parts develop proportionately.

Dwarfism may be unaccompanied by other symptoms, or it may occur together with other problems physical and mental.

DEMOGRAPHICS

Dwarfism as a result of achondroplasia occurs in about 1 in every 26,000 to 40,000 births.

Dwarfism resulting from spondyloepiphyseal dysplasia (a bone growth disorder that affects the spine and the ends of bones) occurs in approximately 1 in 95,000 births.

Dwarfism resulting from dystrophic dysplasia (a cartilage and bone development disorder that often produces joint deformities) occurs in about 1 in every 100,000 births.

Additionally, infants born with a growth hormone deficiency or brittle bones may be prone to dwarfism.

CAUSES AND SYMPTOMS

More than 200 conditions can cause dwarfism.

Dwarfism is most often caused by either a random genetic mutation in the egg or sperm cell during fetal development or an inherited genetic change passed down by a parent.

Other causes include metabolic, endocrine, and hormonal disorders, such as pituitary gland or kidney malfunction.

Chromosomal abnormalities can also lead to dwarfism. Transmission of maternal rubella and maternal malnutrition may be contributing factors to the development of dwarfism.

Maternal age is also an influence. Environmental factors impacting intrauterine growth include maternal use of drugs, alcohol,

Hypothyroidism can also lead to dwarfism—hypothyroidism results from the insufficient activity of the thyroid gland.

Hypothyroidism can have various causes, including underdevelopment, lack of or extraction of the thyroid gland; shortage of an enzyme important for adequate thyroid function; iodine deficiency; or an underactive pituitary gland.

In addition to retarding growth, hypothyroidism can cause intellectual disabilities if thyroid hormones are not administered in the initial few months of a baby’s life.

If the condition is left untreated, it causes impaired mental development in 50% of affected children by six months.

DIAGNOSIS

Doctors can order several tests to determine if a child has dwarfism. As a general measure, physicians usually keep updated measurements of the child to analyze their growth speed.

Other factors can alert the doctor to the child’s condition, including facial and skeletal structure. X-rays and other imaging studies can be used to determine if any abnormalities exist in the skull or skeleton.

The doctor may also utilize magnetic resonance imaging (MRI) to examine the pituitary gland and hypothalamus.

Abnormalities in these areas often indicate a growth hormone deficiency. Hormone and genetic testing help establish an accurate diagnosis.

TREATMENT

Since growth problems are so varied, there are a wide variety of treatments for them. Some standard therapies include nutritional changes, medications to treat underlying conditions, and (if appropriate) hormone replacement therapy.

“HGH,” the growth hormone for therapeutic purposes, was initially derived from deceased persons’ pituitary glands.

Anyhow, natural growth hormone was prohibitively expensive and presented health hazards thanks to contamination properties. 

In the 1980s, men who received growth hormone therapy in childhood were found to have developed Creutzfeldt-Jakob disease, a fatal neurological disorder.

Since then, natural growth hormone has been replaced by a biosynthetic hormone that received FDA approval in 1985.

PROGNOSIS

People with dwarfism-related conditions often never grow beyond 5 ft (1.5 m).

Individuals with dwarfism are usually of average intelligence and lifespan but are at risk for fluid buildup in the brain.

Some individuals develop clubfoot, a condition in which one or both feet are deformed.

Most people with dwarfism inherit one usual copy of a growth gene and one mutated copy of a growth gene.

If a fetus inherits a mutated gene from both parents, its survival rate is usually shallow.

PREVENTION

Most causes of dwarfism are impossible to prevent because they are genetically manifested.

Parents can undergo genetic testing to assess whether their children are at risk of developing dwarfism.

Parents with achondroplasia can also receive genetic counseling to understand the dangers of childbearing better.

Achondroplasia often generates randomly, however, and is generally unpreventable.

PARENTAL CONCERNS

Adults with a family history of achondroplasia should speak to a healthcare provider when deciding to have children.

Parents with achondroplasia have a 50% chance of passing the gene on to their offspring.

If both parents have achondroplasia, the likelihood increases to 75%. However, parents who do not have achondroplasia can also produce children with dwarfism.

Final Words

QUESTIONS TO ASK YOUR DOCTOR

  • What are the causes of dwarfism?
  • What are some complications of dwarfism?
  • What tests are needed to diagnose dwarfism?
  • What is the average lifespan of a person with dwarfism?
  • What are some genetic indications that a child may be at risk of developing dwarfism?

Resources

Defendi, Germaine L. “Genetics of Achondroplasia.” Medscape. http://emedicine.medscape.com/article/941280-overview (accessed April 27, 2020).

Kaneshiro, Neil K., ed. “Achondroplasia.” Medline Plus, U.S. National Library of Medicine. http://www.nlm.nih.gov/medlineplus/ency/article/001577.htm (accessed April 27, 2020).

Kemp, Stephen. “Pediatric Growth Hormone Deficiency.” eMedicine.comhttp://www.emedicine.com/ped/topic1810.htm (accessed April 27, 2020).

KidsHealth. “Dwarfism.” KidsHealth, The Nemours Foundation. http://kidshealth.org/parent/medical/bones/dwarfism.html# (accessed April 27, 2020).

Mayo Clinic staff. “Dwarfism.” Mayo Clinic. http://www.mayoclinic.org/diseases-conditions/dwarfism/basics/definition/con-20032297 (accessed April 27, 2020).

MedlinePlus. “Dwarfism,” MedlinePlus, U.S. National Library of Medicine. http://www.nlm.nih.gov/medlineplus/dwarfism.html (accessed April 27, 2020).

WebMD. “Dwarfism.” WebMD. http://www.webmd.com/children/dwarfism-causes-treatments (accessed April 27, 2020).