An Overview of Hypoplasia

An Incomplete Development of an Organ or Tissue in the Body

Closeup of a cardiac monitor

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In This Article

Hypoplasia is a term describing the incomplete development of an organ or tissue in the body. In this sense, it’s more of a descriptor than a specific disease, though it may be the dominating feature of one. This underdevelopment is congenital—meaning it arises when the fetus is still in the womb—and can be seen in everywhere from tooth enamel (a condition called Turner’s hypoplasia) to the corpus callosum of the brain, heart, ovaries, various muscle groups, and other regions. Symptoms and treatment vary depending on the location of the hypoplasia.

Medically speaking, it’s differentiated from aplasia, a complete absence of an organ, but depending on location, it can be no less serious. Since the causes are genetic in nature, there are few if any options in preventing this underdevelopment.

Types of Hypoplasia

Largely, the impact of the hypoplasia is determined by which specific organ system is involved. This condition can strike anywhere in the body, but there are several types that are of particular concern.

Hypoplasia of the Nervous and Ocular Systems

  • Cerebellar hypoplasia: This is a relatively rare congenital condition in which the cerebellum of the brain—the "little brain" portion located at the top of the spinal column—is underdeveloped. It first arises during embryonic brain development, and the severity of symptoms depends on the extent of the condition.
  • Hypoplasia of corpus callosum: Also known as white matter hypoplasia or corpus callosum agenesis, this is an underdevelopment of the corpus callosum, which is the inner brain region that connects the right and left hemispheres. It may lead to unusual facial appearance, intellectual disability, and reduced size of the corpus callosum itself.
  • Optic nerve hypoplasia: Also known as DeMorsier’s syndrome, this disorder is characterized by incomplete development of the nerves regulating vision in the eye. Not only can this lead to blindness—it’s the cause of serious vision loss in 15 to 25% of infants  —it is paired with endocrine problems, pituitary gland issues, and hypoplasia of the corpus callosum.

Hypoplasia in Other Major Organ Systems

  • Hypoplastic left heart syndrome: This is when one side of the heart does not form fully while the body is still forming in the womb. Hypoplastic left heart syndrome (HLHS) occurs on the left side, in either the left ventricle, mitral valves, aortic valve, or aorta, rendering the organ unable to properly pump blood. This is a critical and potentially fatal condition, requiring immediate medical attention.
  • Hypoplastic right heart syndrome: As with HLHS, hypoplastic right heart syndrome (HRHS) is an underdevelopment of the major chambers and structures of the right side of the heart, including the tricuspid valve, right ventricle, and/or pulmonary valve. Most notably, this seriously affects the amount of blood that reaches the lung and is very dangerous.
  • Hypoplastic coronary artery disease: This relatively rare condition is characterized by poor development of the circumflex and/or coronary arteries. These major arteries supply the muscles of the heart and are therefore essential to overall health. The symptoms of hypoplastic coronary artery disease resemble those of other serious cardiac problems and are seen as a medical emergency.
  • Pulmonary hypoplasia: Another defect seen at birth, pulmonary hypoplasia is an incomplete development of the tissue that comprises the lungs. Occurring in one lung (unilateral) or both (bilateral), this condition reduces the capacity of the body to access the oxygen it needs, and often requires immediate medical attention.

Other Types of Hypoplasia

  • Hypoplastic breast: In contrast to most other types of hypoplasia, this one—characterized by incomplete development of the breasts in women—isn’t seen until puberty. Though not lethal, reconstructive surgery may be called for in these cases.
  • Ovarian hypoplasia: As with hypoplastic breast, ovarian hypoplasia is first seen as girls enter puberty. Alongside underdevelopment of the ovaries, a crucial part of the female reproductive apparatus, this condition can be paired with irregular or absent menstruation as well as abnormal development of other secondary sex characteristics. This issue can be seen in cases that lead to premature infertility.
  • Testicular hypoplasia: In boys, there may be a variety of reasons for the underdevelopment of the testes, but it’s often be seen in cases of a genetic disorder called Klinefelter syndrome. In these cases, males are born with an extra “X” chromosome; this means that instead of the usual X and Y sex chromosomes that determine male sex, there’s an extra one (making it XXY). Among the symptoms of this issue is the improper development of the testes, which can lead to infertility.

Symptoms

As noted above, the symptoms of hypoplasia depend on what part of the body is affected; in some cases these can be very dangerous, while in others the condition is relatively asymptomatic.

Symptoms of Hypoplasia of the Nervous and Ocular System

  • Cerebellar hypoplasia: Abnormal ocular (eye) movements, poor muscle tone (hypotonia), and ataxia (lack of coordination).
  • Hypoplasia of the corpus callosum: Developmental and speech delay, smaller than usual skull and lower jaw, wide-set eyes, shorter stature, and wide nasal bridge, among others.
  • Optic nerve hypoplasia: Moderate to severe vision loss is a hallmark; may arise alongside endocrine abnormalities, developmental delays, cerebral palsy, and seizure.

Symptoms of Major Organ Hypoplasia

  • Hypoplastic left heart syndrome: In infants, problems breathing, pounding heart, weak pulse, ashen or bluish-colored skin. This condition is considered a medical emergency.
  • Hypoplastic right heart syndrome: Also requiring immediate attention, the symptoms are grayish-blue colored skin, lips, and fingernails, breathing problems, poor feeding, low activity and drowsiness, cold hands and feet.
  • Hypoplastic coronary artery disease: Loss of consciousness, labored breathing, rapid or irregular heartbeat; can lead to death if untreated.
  • Pulmonary hypoplasia: Depending on the degree of hypoplasia, symptoms include difficulty breathing, blue lips and toenails, and a sunken chest.

Symptoms of Other Types of Hypoplasia

  • Hypoplastic breast: Narrow, widely-spaced breasts; swollen, puffy areolas; asymmetry of the breast
  • Ovarian hypoplasia: Abdominal pain, small or absent vaginal opening, failure to start having periods at puberty, and infertility
  • Testicular hypoplasia: Reduced size of the testes, infertility

Causes

As noted above, hypoplasia accompanies a variety of conditions and varies based on location; however, as underdevelopment of an organ or tissue, it always has a genetic origin.

This means that these issues arise from errors or inconsistencies in the genes, which essentially lay out the roadmap of the body’s development and function. As such, aspects like a family history of the disease or condition may increase the likelihood of the specific hypoplasia’s development.

Diagnosis

Diagnostic methods for hypoplasia vary based on the affected region.

  • Neurological hypoplasia: Cerebellar hypoplasia and hypoplasia of the corpus callosum are detected initially via an analysis of the relevant symptoms with diagnosis confirmed using brain imaging techniques such as MRI or CT scan.
  • Optic nerve hypoplasia: This hypoplasia is detected through direct examination of the eye by an ophthalmologist.
  • Cardiac hypoplasia: Hypoplasia that occurs in the heart is diagnosed initially through an assessment of symptoms in the infant, followed by analysis using an echocardiogram, which is an ultrasound imaging test.
  • Pulmonary hypoplasia: If pulmonary hypoplasia is suspected in an infant, doctors will use X-ray or CT scan imaging is used to confirm results. Ultrasound or MRI may also sometimes be used.
  • Breast and testes hypoplasia: Hypoplasia of the breast and testes are diagnosed visually.
  • Ovarian hypoplasia: There is a range of tests that may be necessary to assess for this type of hypoplasia, including the follicle-stimulating hormone, estradiol, and prolactic tests (measuring estrogen and other key hormone levels) as well as two more genetic tests: the karyotype and FMR1 gene test.

Treatment

The treatment of hypoplasia depends a great deal on the specific part of the body affected. As yet, preventative approaches—something like a genetic repair of the issue—are not available, so doctors take these issues on after they’ve developed and been detected. This kind of management of symptoms can include everything form taking certain medications, increasing airflow to the lungs (in cases of pulmonary hypoplasia), and boosting nutrition levels.

Notably, genetic testing during pregnancy can detect many forms of hypoplasia; this can be helpful in preparing parents for the necessary care that will be needed after birth. If caught in a timely fashion—and if the condition is likely to be lethal to the infant—termination of pregnancy may be considered.

Since these issues often arise congenitally, treatments often have to be administered shortly after birth.

Surgery may occasionally be necessary to take on heart defects like hypoplastic left or right heart syndrome. There are a couple different procedures, which are often used in conjunction with one another:

  • Norwood Procedure: In cases of hypoplastic left heart syndrome, this surgery can be performed within the first two weeks of an infant's life. Basically, it involves creating an aorta (the body's largest artery that pumps blood away from the heart) to connect to the right ventricle. This allows blood to be pumped throughout the body.
  • Glenn Shunt Procedure: The aim of this surgery, typically performed before the infant is six months old, is to connect the pulmonary artery, which pumps oxygenated blood out to the body, and the pulmonary vessel, which brings deoxygenated blood from the upper body back to the lungs. This will reduce the amount of work the right ventricle has to do.
  • Fontan Procedure: Similar to the Glenn shunt procedure, the pulmonary artery and vein are connected. The difference is that this procedure works to ensure deoxygenated blood from the lower half of the body gets back to the heart and lungs.

There are fewer options available for hypoplasia involving the brain, though therapies do exist to take on the symptoms.

A Word From Verywell

Since many forms of hypoplasia are detected at birth, this issue can be a very frightening one for parents to face. It’s anguishing to see suffering on day one.

But there is hope; not only are doctors today better than ever before at detecting these kinds of problems, treatments—surgical or otherwise—are also getting better as medicine continues to progress. Help is there, and outcomes are always improving.

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Article Sources

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