Tay-Sachs and Sandhoff diseases
Tay-Sachs and Sandhoff diseases are inherited diseases of the central nervous system. These diseases have the same symptoms, though they are caused by mutations (changes) in different genes. A severe form of each disease can affect babies and is fatal.
Babies with the classic (infantile) forms of Tay-Sachs and Sandhoff diseases appear healthy at birth and seem to develop normally for the first few months of life. Symptoms generally appear by about 6 months of age when the baby gradually stops smiling, crawling, turning over and reaching out. The baby continues to lose skills gradually and eventually becomes blind, paralyzed and unaware of surroundings. Babies with Tay-Sachs disease usually die by age 4; those with Sandhoff disease, by age 3 (National Institute of Neurological Disorders and Stroke (NINDS), 2007; NINDS, 2009; Online Mendelian Inheritance in Man #268800, 2009).
Babies with classic Tay-Sachs and Sandhoff diseases lack an enzyme (protein) called hexosaminidase. There are two versions of this enzyme, hex A and hex B. Babies with Tay-Sachs disease do not make hex A, and babies with Sandhoff disease do not make either hex A or hex B. A small number of babies with Tay-Sachs disease (AB variant) make both versions of the enzyme but lack another protein that is needed for these enzymes to work properly.
Hexosaminidase is necessary for breaking down certain fatty substances (called GM2 gangliosides) in cells of the brain. Without this enzyme, these fatty substances build up and gradually destroy brain cells, until the entire central nervous system stops working.
There are late-onset forms of these diseases, with symptoms developing in childhood or adulthood. While babies with the classic forms of these diseases do not produce any enzyme, individuals with the late-onset forms produce very small amounts. This is probably why their symptoms begin later in life and generally are milder than in the classic form.
There are three late-onset forms of Tay-Sachs disease:
- Juvenile (subacute): Symptoms begin between 2 and 10 years of age and resemble those of the classic form (Kaback, 2006; Online Mendelian Inheritance in Man, #272800, 2009). Although the course of the disease is slower, death generally occurs by age 15 (Online Mendelian Inheritance in Man, #272800, 2009; Maegawa, 2006).
- Chronic: Symptoms begin by age 10 and progress slowly (Kaback, 2006). Symptoms vary and may include poor coordination, unsteady gait, muscle cramps, slurred speech and, sometimes, mental illness. Cognitive abilities may not be affected or may be affected late in the course of the disease (Kaback, 2006). Life expectancy varies (Chicago Center for Jewish Genetic Disorders, 2007).
- Adult-onset: This is the mildest form with symptoms developing in adolescence or adulthood. Symptoms vary greatly in severity and can include slurred speech, muscle weakness, muscle cramps, tremors, unsteady gait and, sometimes, mental illness (Kaback, 2006; National Tay-Sachs and Allied Diseases Association, Inc., 2009). Affected individuals usually do not lose vision or hearing. Some individuals may have loss of certain mental abilities, including problems with memory. Life expectancy varies and, in some cases, appears to be unaffected (Kaback, 2006; National Tay-Sachs and Allied Diseases Association, Inc., 2009).
Late-onset forms of Sandhoff disease are rare and appear to share many of these symptoms.
There is currently no treatment to prevent these diseases from running their course. Affected individuals can be made as comfortable as possible and given other supportive care.
Researchers are investigating whether stem cell transplants could help babies with classic Tay-Sachs and Sandhoff diseases. Stem cells are immature blood cells that produce all other kinds of blood cells. Stem cells are obtained from umbilical cord blood or from the bone marrow of a donor. Unfortunately, stem cell transplantation has not yet been successful in stopping or reversing brain damage in Tay-Sachs or Sandhoff diseases, and this treatment poses a high risk of death in affected babies (NINDS, 2007; NINDS, 2009).
Researchers also are studying the effectiveness of drug treatments (including a drug called miglustat, which is approved by the Food and Drug Administration to treat a related disorder) to help reduce the build-up of fatty substances in brain cells in individuals with these diseases (National Tay-Sachs and Allied Diseases Association, Inc., 2009).
Tay-Sachs disease occurs most frequently in descendants of Central and Eastern European (Ashkenazi) Jews. About 1 out of every 30 American Jews carries a mutation in the gene that codes for hex A (Kaback, 2006; American College of Obstetricians and Gynecologists (ACOG), 2005). Some non-Jewish individuals of French-Canadian ancestry (from the St. Lawrence River Valley of Quebec) and members of the non-Jewish Cajun population in Louisiana and the Old Order Amish in Pennsylvania also are at increased risk (Kaback, 2006; American College of Obstetricians and Gynecologists (ACOG), 2005). Individuals in other ethnic groups in this country have about a 1 in 300 chance of carrying a mutation in this gene (Kaback, 2006; American College of Obstetricians and Gynecologists (ACOG), 2005).
Sandhoff disease can occur in any ethnic group, though it is uncommon. Individuals not of Jewish ancestry are more likely than those of Jewish ancestry (1 in 600 vs. 1 in 1,000) to carry one of the gene mutations that cause Sandhoff disease (Online Mendelian Inheritance in Man #268800, 2009).
All forms of Tay-Sachs and Sandhoff diseases are inherited. Tay-Sachs disease is caused by mutations in a gene on chromosome 15 that codes for hex A. Sandhoff disease is caused by mutations in a gene on chromosome 5 that codes for hex B. Both diseases are passed on through parents who carry one of these mutations. A carrier does not have the illness. However, when two carriers become parents:
- There is a 25-percent (1 in 4) chance that any child they have will inherit a gene mutation from each parent and have the disease.
- There is a 25-percent chance (1 in 4) that the child will inherit the normal gene from each parent. The child will not have the disease and will not be a carrier.
- There is a 50-percent (2 in 4) chance that the child will inherit one normal and one abnormal gene. The child will not have the disease but will be a carrier like the parents.
If only one parent is a carrier, the couple’s children cannot inherit the disease. However, each child has a 50-percent chance of inheriting the gene mutation and being a carrier.
Carrier screening is commonly performed before or during pregnancy for adults in populations who are at risk for these disorders.
An individual can take a test that measures the amount of hexosaminidase in the blood. Tay-Sachs carriers have about half as much of hex A as noncarriers, but this is plenty for the carrier’s own needs. Similarly, carriers of Sandhoff disease have reduced but adequate amounts of both hex A and hex B.
A blood sample can be used to perform DNA-based genetic testing for known mutations in the hex A and hex B genes. Genetic testing may be recommended if the results of the carrier screening test are uncertain.
Carrier screening is available from a genetic services center or clinic. A health care provider can provide referrals to local sites where testing is available, as can the National Tay-Sachs and Allied Diseases Association.Trained genetic counselors explain test results so that individuals know whether or not their children are at risk for the disease.
Yes. Prenatal tests called chorionic villus sampling (CVS) and amniocentesis can diagnose these diseases before birth. These tests are available when both members of a couple are carriers or when one is a carrier and the other has uncertain or unknown carrier status.
CVS generally is done between 10 and 12 weeks of pregnancy. In CVS, the doctor retrieves a sample of cells from the developing placenta either through a thin tube inserted through the vagina or by inserting a needle through the mother’s abdomen. The placenta contains cells that are genetically identical to those of the fetus, and these cells are examined for the presence of hex A (when testing for Tay-Sachs) or hex A and hex B (when testing for Sandhoff). The lab can test for gene mutations in addition to the enzyme.
Amniocentesis usually is done between 15 and 20 weeks of pregnancy. In this test, the doctor inserts a needle into the mother’s abdomen to take a sample of fluid that surrounds the fetus. The fluid contains fetal cells, which are tested for the presence of the enzyme and/or gene mutations.
Some medical centers offer genetic testing to carrier couples who undergo in vitro fertilization (a process in which eggs are removed from a woman’s ovaries and fertilized in the laboratory with her partner’s sperm). The embryos are tested for a genetic disease, and only healthy ones are implanted in the mother. This is called preimplantation genetic testing.
Couples who are carriers of a Tay-Sachs or Sandhoff gene or those who may be at increased risk due to ethnic background or family history may want to consult a genetic counselor. These health professionals help families understand what is known about the causes of a birth defect and the chances of the birth defect occurring in a pregnancy. They also help guide families through the testing process. Genetic counselors can provide referrals to medical experts and appropriate support groups in the community. Genetic counseling is available at most large medical centers and teaching hospitals. To find a genetic counselor in their area, individuals can ask their health care provider or contact the National Society of Genetic Counselors.
Yes. March of Dimes grantees helped pinpoint mutations in the hex A gene that are responsible for late-onset forms of Tay-Sachs disease. Information about specific mutations leads to improved diagnosis and carrier screening for all forms of Tay-Sachs disease.
Current grantees are attempting to develop drug treatments that may prevent the production of certain fatty substances that build up and impair brain cells in individuals with Tay-Sachs and Sandhoff diseases. This approach eventually may help prevent the loss of central nervous system function and early deaths associated with these diseases.
- American College of Obstetricians and Gynecologists (ACOG). (2005). Screening for Tay-Sachs disease. (ACOG Committee Opinion, volume 318, reaffirmed 2007).
- Chicago Center for Jewish Genetic Disorders. (2007). Tay-Sachs disease. Retrieved September 7, 2007 from: jewishgenetics.org/?q=content/tay-sachs-disease.
- Kaback, M.M. (2006). Hexosaminidase A deficiency. GeneReviews. Retrieved June 23, 2009 from: ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=tay-sachs.
- Maegawa, G.H.B. (2006). The natural history of juvenile or subacute GM2 gangliosidosis: 21 new cases and literature review of 134 previously reported. Pediatrics, 118, e1550-e1562.
- National Institute of Neurological Disorders and Stroke (NINDS). (2009). NINDS Sandhoff disease information page. Retrieved April 19, 2009 from: ninds.nih.gov/disorders/sandhoff/sandhoff.htm.
- National Institute of Neurological Disorders and Stroke (NINDS). (2007). NINDS Tay-Sachs disease information page. Retrieved December 2, 2009 from: ninds.nih.gov/disorders/taysachs/taysachs.htm.
- National Tay-Sachs and Allied Diseases Association, Inc.(2009). What is Tay-Sachs disease? Retrieved June 23, 2009 from: ntsad.org.
- Online Mendelian Inheritance in Man. (2009). Sandhoff disease #268800. Retrieved April 10, 2009 from: http://omim.org/entry/268800.
- Online Mendelian Inheritance in Man. (2009). Tay-Sachs disease #272800. Retrieved March 5, 2009 from: http://omim.org/entry/272800.
Most common questions
Can dad's exposure to chemicals harm his future kids?
Dad's exposure to harmful chemicals and substances before conception or during his partner's pregnancy can affect his children. Harmful exposures can include drugs (prescription, over-the-counter and illegal drugs), alcohol, cigarettes, cigarette smoke, chemotherapy and radiation. They also include exposure to lead, mercury and pesticides.
Unlike mom's exposures, dad's exposures do not appear to cause birth defects. They can, however, damage a man's sperm quality, causing fertility problems and miscarriage. Some exposures may cause genetic changes in sperm that may increase the risk of childhood cancer. Cancer treatments, like chemotherapy and radiation, can seriously alter sperm, at least for a few months post treatment. Some men choose to bank their sperm to preserve its integrity before they receive treatment. If you have a question about a specific exposure, contact the Organization of Teratology Information Specialists at www.otispregnancy.org.
Can Rh factor affect my baby?
The Rh factor may be a problem if mom is Rh-negative but dad is Rh-positive. If dad is Rh-negative, there is no risk.
If your baby gets her Rh-positive factor from dad, your body may believe that your baby's red blood cells are foreign elements attacking you. Your body may make antibodies to fight them. This is called sensitization.
If you're Rh-negative, you can get shots of Rh immune globulin (RhIg) to stop your body from attacking your baby. It's best to get these shots at 28 weeks of pregnancy and again within 72 hours of giving birth if a blood test shows that your baby is Rh-positive. You won't need anymore shots after giving birth if your baby is Rh-negative. You should also get a shot after certain pregnancy exams like an amniocentesis, a chorionic villus sampling or an external cephalic version (when your provider tries to turn a breech-position baby head down before labor). You'll also want to get the shot if you have a miscarriage, an ectopic pregnancy or suffer abdominal trauma.
Does cleft lip or cleft palate cause dental problems?
A cleft lip or cleft palate that extends into the upper gums (where top teeth develop) can cause your baby to have certain dental problems, including:
- Missing teeth
- Too many teeth
- Oddly shaped teeth
- Teeth that are out of position around the cleft
Every baby with a cleft lip or palate should get regular dental checkups by a dentist with experience taking care of children with oral clefts. Dental problems caused by cleft lip or palate usually can be fixed. If needed, your baby can get ongoing care by a team of experts, including:
- A dentist
- An orthodontist to move teeth using braces
- An oral surgeon to reposition parts of the upper jaw, if needed, and to fix the cleft
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause ear problems?
Cleft lip does not cause ear problems.
Babies with cleft palate, however, are more likely than other babies to have ear infections and, in some cases, hearing loss. This is because cleft palate can cause fluid to build up in your baby’s middle ear. The fluid can become infected and cause fever and earache. If fluid keeps building up with or without infection, it can cause mild to moderate hearing loss.
Without treatment , hearing loss can affect your baby’s language development and may become permanent.
With the right care, this kind of hearing loss is usually temporary. Your baby’s provider may recommend:
- Having your baby’s ears checked regularly for fluid buildup
- Medicines for treating fluid buildup and ear infections
- Ear tubes if your baby has fluid in his ears over and over again. Ear tubes are tiny tubes that are inserted into the eardrum to drain the fluid and help prevent infections.
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause problems with breastfeeding?
Babies with only a cleft lip usually don’t have trouble breastfeeding. Most of the time, they can breastfeed just fine. But they may need some extra time to get started.
Babies with cleft lip and palate or with isolated cleft palate can have:
- Trouble sucking strong enough to draw milk through a nipple
- Problems with gagging or choking
- Problems with milk coming through the nose while feeding
Most babies with cleft palate can’t feed from the breast. If your baby has cleft palate, he can still get the health benefits of breastfeeding if you feed him breast milk from a bottle. Your provider can show you how to express (pump) milk from your breasts and store breast milk.
Your baby’s provider can help you start good breastfeeding habits right after your baby is born. She may recommend:
- Special nipples and bottles that can make feeding breast milk from a bottle easier
- An obturator. This is a small plastic plate that fits into the roof of your baby’s mouth and covers the cleft opening during feeding.
See also: Cleft lip and cleft palate, Breastfeeding
Does cleft lip or cleft palate cause speech problems?
Children with cleft lip generally have normal speech. Children with cleft lip and palate or isolated cleft palate may:
- Develop speech more slowly
- Have a nasal sound when speaking
- Have trouble making certain sounds
Most children can develop normal speech after having cleft palate repair. However, some children may need speech therapy to help develop normal speech.
See also: Cleft lip and cleft palate
What are choroid plexus cysts?
The choroid plexus is the area of the brain that produces the fluid that surrounds the brain and spinal cord. This is not an area of the brain that involves learning or thinking. Occasionally, one or more cysts can form in the choroid plexus. These cysts are made of blood vessels and tissue. They do not cause intellectual disabilities or learning problems. Using ultrasound, a health care provider can see these cysts in about 1 in 120 pregnancies at 15 to 20 weeks gestation. Most disappear during pregnancy or within several months after birth and are no risk to the baby. They aren't a problem by themselves. But if screening tests show other signs of risk, they may indicate a possible genetic defect. In this case, testing with higher-level ultrasound and/or amniocentesis may be recommended to confirm or rule out serious problems.
What if I didn't take folic acid before pregnancy?
If you didn’t take folic acid before getting pregnant, it doesn't necessarily mean that your baby will be born with birth defects. If women of childbearing age take 400 micrograms of folic acid every day before and during early pregnancy, it may help reduce their baby’s risk for birth defects of the brain and spin called neural tube defects (NTDs). But it only works if you take it before getting pregnant and during the first few weeks of pregnancy, often before you may even know you’re pregnant.
Because nearly half of all pregnancies in the United States are unplanned, it's important that all women of childbearing age (even if they're not trying to get pregnant) get at least 400 micrograms of folic acid every day. Take a multivitamin with folic acid before pregnancy. During pregnancy, switch to a prenatal vitamin, which should have 600 micrograms of folic acid.
Last reviewed November 2012