There are different types of inherited disorders Inheritance of Single-Gene Disorders Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are made of a very long strand... read more . In Tay-Sachs disease and Sandhoff disease, both parents of the affected child carry a copy of the abnormal gene. Because usually two copies of the abnormal gene are necessary for the disorder to occur, usually neither parent has the disorder. (See also Overview of Hereditary Metabolic Disorders Overview of Hereditary Metabolic Disorders Hereditary metabolic disorders are inherited genetic conditions that cause metabolism problems. Heredity is the passing of genes from one generation to the next. Children inherit their parents'... read more .)
Sphingolipidoses occur when people do not have the enzymes needed to break down (metabolize) sphingolipids, which are compounds that protect the cell surface and serve certain functions in the cells. There are many other types of sphingolipidoses:
In Tay-Sachs disease and Sandhoff disease, gangliosides, which are products of fat metabolism, accumulate in brain tissue. Gangliosides build up in affected children because the enzyme needed to break down gangliosides, called hexosaminidase A, is not working correctly.
This disease is most common among families of Eastern European (Ashkenazi) Jewish origin.
Children with this disease start missing developmental milestones Developmental Milestones From Birth to Age 12 Months* Between the ages of 1 and 13, children's physical, intellectual, and emotional capabilities expand tremendously. Children progress from barely tottering to running, jumping, and playing organized... read more after 6 months of age and become progressively intellectually disabled, meaning that intellectual disability Intellectual Disability Intellectual disability is significantly below average intellectual functioning present from birth or early infancy, causing limitations in the ability to conduct normal activities of daily... read more gets worse throughout the life of the child, and appear to have floppy muscle tone. Muscle tightness and stiffness develop, followed by paralysis, dementia, and blindness. These children usually die by age 5.
Before conception, parents can find out whether they are carriers of the gene that causes the disease. Carriers Carrier Screening Genetic screening is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder. Hereditary genetic disorders are disorders of chromosomes or... read more are people who have an abnormal gene for a disorder but who do not have symptoms or visible evidence of the disorder. People who carry the gene should receive genetic counseling because there is a risk they will pass the disorder on to their children. The disease develops when both parents are carriers.
During pregnancy, Tay-Sachs disease can be identified in the fetus by the prenatal screening tests chorionic villus sampling Chorionic Villus Sampling Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more or amniocentesis Amniocentesis Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more .
After birth, blood tests can be done to determine levels of the missing enzyme hexosaminidase A or to analyze the DNA DNA Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells... read more .
The disease cannot be treated or cured.
This disease is very similar to Tay-Sachs disease. However, unlike Tay-Sachs disease, Sandhoff disease is not associated with any specific ethnicities.
Beginning at 6 months of age, children become progressively intellectually disabled and blindness develops. Sounds may seem abnormally loud (a condition called hyperacusis). Children also have an enlarged liver and bone problems.
Diagnosis of Sandhoff disease is the same as for Tay-Sachs disease.
The disease cannot be treated or cured.