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An introduction to the issue of the disease tay sachs

Subdivisions of Tay Sachs Disease Infantile Tay-Sachs Disease Late-Onset Tay-Sachs Disease General Discussion Tay-Sachs disease is a rare, neurodegenerative disorder in which deficiency of an enzyme hexosaminidase A results in excessive accumulation of certain fats lipids known as gangliosides in the brain and nerve cells. This abnormal accumulation of gangliosides leads to progressive dysfunction of the central nervous system.

This disorder is categorized as a lysosomal storage disease.

Lysosomes are the major digestive units in cells. Enzymes within lysosomes break down or "digest" nutrients, including certain complex carbohydrates and fats. When an enzyme like hexosaminidase A, which are needed to breakdown certain substances like fats, are missing or ineffective, they build up in the lysosomal. When too much fatty material builds up in the lysosome, it becomes toxic destroying the cell and damaging surrounding tissue. Symptoms associated with Tay-Sachs disease may include an exaggerated startle response to sudden noises, listlessness, loss of previously acquired skills i.

As the disease progresses, affected infants and children may develop cherry-red spots within the middle layer of the eyes, gradual loss of vision, and hearing loss, increasing muscle stiffness and restricted movements spasticityeventual paralysis, uncontrolled electrical disturbances in the brain seizuresand deterioration of cognitive processes dementia. The classical form of Tay-Sachs disease occurs during infancy. This is the most common form and is usually fatal during early childhood.

There are also juvenile and adult forms of Tay-Sachs disease, but these are rare.

  1. In most cases, the earlier the first signs are observed, the more quickly the disease will progress.
  2. If one child is diagnosed with Infantile Tay-Sachs, the other children are only at risk for the infantile form.
  3. Symptoms in infants may include feeding problems, general weakness, and an exaggerated startle reflex in response to sudden loud noise. As late-onset Tay-Sachs disease progresses, affected individuals may experience problems with walking, running, and other similar activities.
  4. Several different genetically determined enzyme defects can cause the syndrome, initially described more than 60 years ago. As affected infants age, they may experience slow growth, progressive muscle weakness, diminished muscle tone hypotonia , and diminished mental functioning.

Children with the juvenile form, also called the subacute form, develop symptoms later than those with the infantile form, and they usually live until later in childhood or adolescence. The adult form, also called late-onset Tay-Sachs disease, may occur anytime from adolescence to the mid-30s. The symptoms and severity can vary from one person to another. Some people may fall in between the juvenile and adult forms.

Tay-Sachs disease is inherited in an autosomal recessive manner. The disorder results from changes mutations of a gene known as the HEXA gene, which regulates production of the hexosaminidase A enzyme. The HEXA gene has been mapped to the long arm q of chromosome 15 15q23-q24.

  1. There are very rare forms where symptoms begin later in childhood, adolescence or adulthood. Children with the juvenile form, also called the subacute form, develop symptoms later than those with the infantile form, and they usually live until later in childhood or adolescence.
  2. Often, diagnosis is made by a neurologist or geneticist.
  3. As the ability to move becomes progressively impaired, people with this disease are at increased risk for respiratory failure.
  4. Affected Populations Tay-Sachs disease affects males and females in equal numbers.

There is no cure for Tay-Sachs disease, and the treatment is aimed at relieving the an introduction to the issue of the disease tay sachs symptoms that occur. Another name for Tay-Sachs disease is GM2 gangliosidosis type 1. There are two other, related disorders, called Sandhoff disease and hexosaminidase activator deficiency that are indistinguishable from Tay-Sachs disease based on symptoms and can only be differentiated through testing to determine the underlying cause.

These two disorders are also cause reduced activity of hexosaminidase, but are caused by changes in different genes. Collectively, these three disorders are known as GM2 gangliosidoses.

In individuals with infantile Tay-Sachs disease, symptoms typically first appear between three and five months of age. In individuals with the late-onset form, symptoms may become apparent anytime from adolescence through the mid-30s.

Infantile Tay-Sachs Disease The infantile form of Tay-Sachs disease is characterized by an almost complete lack of hexosaminidase A enzyme activity. The disorder often progresses rapidly, resulting in significant mental and physical deterioration. Infants may appear completely unaffected at birth. Initial symptoms, which usually develop between 3 and 6 months, can include mild muscle weakness, twitching or jerking of muscles myoclonic jerksand an exaggerated startle response, such as when there is a sudden or unexpected noise.

The startle response may be partly due to an increased sensitivity to sound acoustic hypersensitivity. Between six and 10 months, affected infants may fail to gain new motor skills. They may no longer make eye contact and there may be unusual eye movements. They may be listlessness and irritable. As affected infants age, they may experience slow growth, progressive muscle weakness, diminished muscle tone hypotoniaand diminished mental functioning.

Affected infants may also exhibit gradual loss of vision, involuntary muscle spasms that result in slow, stiff movements spasticityand the loss of previously acquired skills i. A characteristic symptom of Tay-Sachs disease is the development of cherry red spots in the eyes.

This condition occurs when the macular cells of the eye deteriorate, exposing the underlying choroid. The choroid is the middle layer of the eye that consists of blood vessels that supply blood to the retina.

Eventually, infants may become unresponsive to their environment and surroundings. By three to five years of age, life-threatening complications may occur such as respiratory failure. Juvenile Subacute Tay-Sachs Disease The onset of this form can be anywhere between two and 10 years of age.

Often, one of the first signs is clumsiness and problems with coordination. Behavioral problems a progressive loss of speech, life skills, and intellectual abilities also develop. Children may or may not develop a cherry-red spot in the eyes. Degeneration of the nerve that carries impulses from the eye to the brain to form images optic atrophy may occur.

Some children may have retinitis pigmentosa, a large group of vision disorders that cause progressive degeneration of the retina, the light-sensitive membrane that coats the inside of the eyes.

Children will become less responsive to their environment and surroundings. Life-threatening complications usually occur around 15 years of age.

Affected individuals will not have all the symptoms listed below. The disorder progresses much slower than the infantile form. The variability of late onset Tay-Sachs may even be seen in members of the same family.

One person may have symptoms in their 20s, while another reaches theirs 60s or 70s with only minor problems with their muscles. Initial symptoms associated with late-onset Tay-Sachs disease may include clumsiness, mood alterations, and progressive muscle weakness and wasting amyotrophy. As affected individuals age, they may exhibit tremors, muscle twitching fasciculationsseizures, slurred speech dysarthriaan inability to coordinate voluntary movements ataxiadifficulty swallowing dysphagiaand a condition known as dystonia.

Dystonia is a group of disorders characterized by involuntary muscle contractions that may force certain body parts into unusual, and sometimes painful, movements and positions.

Some individuals may have involuntary muscle spasms that result in slow, stiff movements spasticity. As late-onset Tay-Sachs disease progresses, affected individuals may experience problems with walking, running, and other similar activities. In severe instances, affected individuals may eventually need assistive devices such as braces or a wheelchair. In some instances, affected individuals may experience mental deterioration, memory problems, and behavioral changes including short attention spans and personality changes.

Genes provide instructions for creating proteins that play a critical role in many functions of the body. When a mutation of a gene occurs, the protein product may be faulty, inefficient, or absent. Depending upon the functions of the protein, this can affect many organ systems of the body, including the brain. More than 80 different mutations of the HEXA gene have been identified in individuals with the disease. Inheriting two mutated copies of the HEXA gene homozygotes causes deficiency of the hexosaminidase A enzyme, which is necessary to breakdown fatty substance lipid known as GM2-ganglioside within cells of the body.

Failure to breakdown GM2-ganglioside results in its abnormal accumulation in brain and nerve cells eventually resulting in the progressive deterioration of the central nervous system. In infantile Tay-Sachs disease, there is an almost complete lack of hexosaminidase A. In late-onset Tay-Sachs disease, there is deficiency of hexosaminidase A enzyme activity. Because there is some enzyme activity, the disorder is less severe and progresses much slower than infantile Tay-Sachs disease. The exact amount of enzyme activity in late-onset Tay-Sachs disease varies greatly from one person to another.

Consequently, the age of onset, severity, specific symptoms, and rate of progression of late-onset Tay-Sachs disease also vary greatly from one person to another. Most genetic diseases are determined an introduction to the issue of the disease tay sachs the status of the two copies of a gene, one received from the father and one from the mother.

Recessive genetic disorders occur when an individual inherits two copies of an abnormal gene for the same trait, one from each parent. If an individual inherits one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk is the same for males and females. Researchers have determined that the gene for Tay-Sachs disease is located on the long arm q of chromosome 15 15q23-q24. Chromosomes are located in the nucleus of human cells and carry the genetic information for each individual.

Introduction to Tay-Sachs

Human body cells normally have 46 chromosomes. Pairs of human chromosomes numbered from 1 through 22 are called autosomes and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Chromosomes are further sub-divided into many bands that are numbered. The numbered bands specify the location of the thousands of genes that are present on each chromosome. Affected Populations Tay-Sachs disease affects males and females in equal numbers.

Tay-Sachs disease occurs with greater frequency among Jewish people of Ashkenazi descent, i. Approximately one in 30 Ashkenazi Jewish people carries the altered gene for Tay-Sachs disease. In addition, one in 300 individuals of non-Ashkenazi Jewish heritage is a carrier. In this specific Jewish population, about one in 3,600 live births is affected.

The disease has also been reported in some individuals of Italian, Irish Catholic, and non-Jewish French Canadian descent, especially those living in the Cajun community of Louisiana and the southeastern Quebec.

In the general population, the carrier rate for the altered gene is approximately 1 in 250-300 people. Late-onset Tay-Sachs disease occur less often than the infantile form. However, rare disorders like late-onset Tay-Sachs disease often go unrecognized. These disorders are under-diagnosed, making it difficult to determine the true frequency of such disorders in the general population.

Related Disorders Symptoms of the following disorders can be similar to those of Tay-Sachs disease. Comparisons may be useful for a differential diagnosis: Sandhoff disease is a rare genetic disorder resulting in the progressive deterioration of the central nervous system neurodegenerative disorder.

A deficiency of the enzymes hexosaminidase A and B results in the accumulation of certain fats lipids in the brain and other organs of the body. The most common form affects infants, usually beginning between three and six months of age. Symptoms in infants may include feeding problems, general weakness, and an exaggerated startle reflex in response to sudden loud noise.

Motor delays, loss of previously acquired skills, and intellectual impairment are progressive.