T AY S ACHS By: Varun Natraj and Kenneth Forward

W HAT IS IT ? Tay Sachs (TSD) is a genetic disorder named after Warren Tay and Bernard Sachs. Tay discovered the red spot in they eye related to TSD while Sachs described the cellular effects. TSD is a fatal disease in infants and juveniles. It is inherited in an autosomal recessive fashion. There are three different variations of Tay Sachs: Infantile TSD Juvenile TSD Late Onset TSD TSD is very rare, with carrier occurrences in the most highly affected populations ranging from one in twenty-seven to one in fifty. In the general population, chances of carrying the disease are one in two hundred and fifty.

G ENERAL S YMPTOMS AND DIAGNOSIS All people affected by TSD have a cherry-red spot on the retina of the eye. It can be easily detected with visual acuity technology. The rest of the symptoms vary based on when each patient is affected. The cherry-red spot is one method to diagnose the disease, while genetic testing is the other.

I NFANTILE TSD Other than the cherry-red spot, it is difficult to detect TSD in infants because they develop normally for the first six months of life. After six months, the disease progress rapidly, resulting in severe deterioration of mental and physical abilities. The child then loses the ability to swallow and will become blind and deaf. Paralysis then occurs and the child usually dies by the age of five.

J UVENILE TSD Juvenile TSD is an extremely rare form of the disorder. If affects children between the ages of They develop with cognitive, motor, and speech difficulties. Swallowing difficulties, unsteadiness of gait, and spasms generally occur as well. Those affected by Juvenile TSD usually die by the age of fifteen, earlier in some cases.

L ATE O NSET TSD Late Onset TSD (LOTS) is also very rare. It occurs in patients in their 20’s – early 30’s. LOTS is sometimes misdiagnosed, and if treated properly in is not fatal. LOTS has many of the same symptoms that characterize juvenile and infantile TSD, but it also includes psychiatric symptoms and neurological deterioration which results in seizures. Patients with LOTS often-times become wheelchair dependent, but they can live full adult lives if the psychiatric and neurological symptoms are properly dealt with.

T REATMENTS There is currently no cure for any form of TSD. LOTS can be slowed and isn’t always fatal, but it cannot be reversed. Due to the fact that TSD is a lysosomal storage disorder, and a genetic mutation, the only possibilities for therapy involve enzyme replacement and gene therapy. If the defective genes could be replaced, theoretically a cure is possible for TSD.

I NHERITANCE Since it is an autosomal inheritance, Tay Sachs can only be passed on if both parents are symptomless genetic carriers and then pass on the gene to their child. The disease is not gender biased. It has the same chance of effecting males and females. Recent research has revealed that Tay Sachs is caused by a mutation on the HEXA gene of chromosome 15. In order for the disease to be passed on the parents must both either have the disease or be carriers of the disease. The disease will not be passed on if one parent is not a carrier, but the children will become carriers.

P UNNETT S QUARE 1 TT TTT tTt In this scenario one parent is neither diseased or a carrier while the other parent is just a carrier. Therefore their children have a 50% chance of being carriers and a 50% chance of being neither carriers or affected. T= no TSD t = TSD

P UNNETT S QUARE 2 TT tTt t In this scenario one parent is neither affected nor a carrier, while the other parent is affected. This is a highly unlikely scenario because most people with Tay Sachs don’t make it past the age of four. If this were to happen the children would have a 100% chance of becoming a carrier, but none would become affected.

P UNNETT S QUARE 3 Tt TTTTt t tt In this scenario both parents are just carriers of TSD. This is the most likely scenario to affect a child in today’s society. In this case the children will have a 25% chance of not being affecter or a carrier, a 50% chance of being a carrier, and a 25% chance of being affected.

P UNNETT S QUARE 4 T t tTt tt tTttt In this scenario, one parent would be an unaffected carrier and the other parent would be affected. This scenario is close to impossible with the rarity of late onset TSD, but if it were to happen the child would have a 50% chance of being a carrier, and a 50% chance of being affected.

P UNNETT S QUARE 5 t t t tt t In this case both parents are affected. This results in a 100% chance of the children being affected. This will probably never happen because it is extremely unlikely that two people with LOTS will get together plus chances are someone with TSD will decide to not have a child with someone else with TSD, knowing that their child is guaranteed to have TSD.

S UPPORT ORGANIZATIONS National Tay Sachs & Allied Diseases Association The Cure for Tay Sachs Foundation March of Dimes asp asp