context: Tay- Sachs disease is a rare, fatal disorder most commonly diagnosed in babies around 6 months of age. There's no cure for the disease, but scientists have a good idea of what causes it, how it worsens, and how to use genetic testing to screen for it early in pregnancy. Researchers are working to make advances in gene therapy or bone marrow transplants that they hope will allow treatment of Tay- Sachs in the future. Defects in a gene called HEXA cause Tay- Sachs. ( You can think of genes as âcodingâ that your parents pass along to you. Genes are in your cells, and they set your body's traits -- everything from your eye color and blood type to your sex.) Most people have two healthy versions of this HEXA gene, which gives instructions to your body to make an enzyme (a type of protein) known as Hex- A. This enzyme prevents the build-up of a fatty substance, called GM2 ganglioside, in the brain and spinal cord. Some people have just one normal copy of the gene, and they still make enough Hex- A protein to keep the brain and spinal cord healthy. But babies born with Tay- Sachs disease inherited a mutated copy of the gene from both parents, so they don't make any Hex- A protein. This is what makes them become so sick. Over time, GM2 ganglioside builds up in their nervous system and starts to cause damage. A baby born with Tay- Sachs grows normally until 3 to 6 months of age. Around this time, parents might notice their baby's development start to slow and the muscles weaken. Gradually, the disease causes more symptoms in babies, including: A loss of motor skills such as turning over, sitting, and crawling A very strong reaction to loud noises Trouble focusing on objects or following them with their eyes Cherry-red spots, which can be identified with an eye examination, in the eyes By age 2, most children with Tay- Sachs have started getting more severe problems. They can include: Swallowing and breathing issues that keep getting worse Seizures Loss of mental function, hearing, and sight Paralysis Past age 3, there are few visible changes in children with Tay- Sachs, but the nervous system continues to go downhill, often leading to death by age 5. There is no cure for this disease. But there are ways to manage symptoms and make life easier for children with Tay- Sachs and their families. Some of the specialists, treatments, and programs you might consider include: Speech language pathologists. They can provide ways to help your baby keep the suck-swallow reflex going as well as help you figure out when it is time to consider a feeding tube for your little one. Neurologists. These specialists can help you manage your baby's seizures with medication. Respiratory health. Specialists such as pediatricians and pulmonologists (doctors who treat lung and breathing problems) can recommend ways for parents to reduce the chance of lung infections in their child. Play and stimulation. You can help your child interact with the world through music, scents, and textures. Massages. They can relax your baby. Palliative and hospice care. These programs help manage quality of life for children with Tay- Sachs and their families. The disease is extremely rare. In the general population, only about 1 in every 112,000 live births is affected. Anyone can be a carrier of a HEXA mutation, meaning they have just one defective copy of the HEXA gene. However, the chance of inheriting the disease is higher in certain groups because of a higher rate of carriers. About 1 in every 27 Jewish people in the United States is a carrier. Non- Jewish French Canadians living near the St. Lawrence River in Canada and in the Cajun community of Louisiana also have a higher incidence of Tay- Sachs. If both parents are carriers of Tay- Sachs disease, there is a 25% chance that any child they have will get the disease. You can have a blood test that analyzes your genes or the levels of the Hex- A protein in your blood to tell you whether you are a carrier. If two people planning to have children find out they're both carriers, a genetic counselor can help them review the options for lowering the chances of having a baby with Tay- Sachs. There's an even rarer type of Tay- Sachs called âlate onsetâ or âadult onset.â It can be hard to diagnosis. Like the version of the disease that affects infants, the Tay- Sachs that starts later in life is caused by HEXA gene mutations. Symptoms might start to appear anywhere from the teen years to adulthood. Early symptoms often include clumsiness, problems balancing, and muscle weakness in the legs. People with it may also have mental health issues. With this form of the disease, life expectancy and the severity of symptoms vary from case to case. Late-onset Tay- Sachs doesn't always shorten life span.