After a long break, Grey’s Anatomy has returned last night, and with it this column covering a disease seen in the last episode. Today’s disease is Tay-Sachs.
Danger level: High
What is it?
Tay-Sachs disease is a rare disorder in which fat accumulates and damages the brain.
Who gets it?
Tay-Sachs is more common in Ashkenazi Jews (before screening tests were started, about 1 out of every 3000 newborns was affected by the disease). It’s also common in Louisiana Cajuns, Pennsylvania Dutch and French Canadians. In other populations it’s much rarer, and occurs in about 1 out of 300,000 newborns.
The disease affects boys and girls to the same extent.
It has 3 forms, each one manifesting at a different age:
- Classic infantile acute form – Starts at 4-8 months of age. This is the most common type.
- Late infantile and juvenile subacute form – Starts at ages 2-10.
- Adult chronic form – Can start anywhere between childhood and adulthood.
What causes it?
Our body produces an enzyme (a molecule that’s responsible for performing a job in the body) called hexosaminidase A. This enzyme is responsible for breaking down compounds made of fat in our body, named gangliosides. When gangliosides aren’t broken down, they accumulate in the nerve cells in the brain causing them to die. In Tay-Sachs disease there is a problem with the enzyme hexosaminidase A, causing gangliosides to accumulate.
Tay-Sachs is a genetic disease, meaning that it runs in families. There are two ways in which genetic diseases can be transferred to children – recessive and dominant. Tay-Sachs is transferred in a recessive way. This means that both parents should have one defective gene in order for the child to get the disease. When both of the parents carry the defective gene, there’s a 25% chance for the child to get Tay-Sachs, as seen in this drawing:
The inheritance of Tay-Sachs disease. Both of the parents are “carriers” of the disease, meaning 1 out of possible 2 genes are defective (if 2 of them were bad, they would have the disease themselves). The child on the right got 2 defective genes – one from each parent, and has the disease. Photo by Cburnett
How does it feel?
Babies with Tay-Sachs appear healthy at birth, but in 3-6 months after birth they start having weakness, or difficulty with movement. They also start having twitches in their eyes.
All patients with Tay-Sachs also have a “cherry-red” spot in the back of their eyes (only visible through am ophthalmoscope):
Everyone who has a child or has followed one since birth know that in the first months and years of life they learn to do different things, such as hold things, crawl, walk. In Tay-Sachs, those things that they learned to do are lost, starting at age 6-10 months.
From there, the disease progresses to seizures, blindness, deafness, paralysis and difficulty with swallowing. These children usually die at age 4-5.
(Please note that, as stated above, there are 2 more, milder types of the disease, which aren’t covered here).
The following video shows Elise Ryne Rochman, who was born December 1, 2004, and diagnosed with Tay-Sachs on November 2005:
You can visit her website here.
How is it discovered?
A blood test that measures the level of the enzyme hexosaminidase A in the blood is performed, in which we will see a low level of the enzyme. To confirm, a genetic test may be done that will show the defective genes.
How is it treated?
Unfortunately, there is no cure for Tay-Sachs disease. Measures to control the symptoms are taken, which may help the child a little.
What happens after treatment?
As mentioned above, these children usually die by age 4-5.
The bottom line – How do I avoid it?
If either you or your partner are Ashkenazi Jews, French Canadians or of Cajun descent, or you have a family history of Tay-Sachs, you should be tested to see if you’re a carrier for the defective gene. If you or your partner turn out positive, it’s important that both of you get tested (since both parents need to carry the gene in order for a child to be sick).
If both of you are carriers, you should consider genetic counseling, since there are ways to discover if the fetus has inherited the disease itself.
What next?
Get free site updates by RSS or by Email, or follow us on Twitter, Facebook or Google Buzz.
Related posts:
- Cystic Fibrosis – A Dangerous Inherited Disease Causing Thick Secretions
- As Seen on Grey’s Anatomy – Acute Porphyria
- As Seen on Grey’s Anatomy – Tethered Spinal Cord Syndrome
- Wilson Disease – The Copper Disease That Could Wreck Your Liver and Brain
- As Seen on Grey’s Anatomy – Melanoma – You Can Avoid It if It’s Found on Time
