An image of a baby in the womb. The first treatment for a baby with spinal muscular atrophy (SMA) was carried out in the womb. (Image credit: PEDRE via Getty Images)
The baby was treated for a rare, potentially life-threatening genetic disorder while still in the womb and has now lived to the age of two without showing any signs of the disease.
This is the first time a condition known as spinal muscular atrophy (SMA) has been treated before birth, according to a new report published Wednesday (Feb. 19) in The New England Journal of Medicine. The baby was diagnosed with SMA type 1, the most common form of the disorder; it has an extremely poor prognosis, usually resulting in death before the baby's second birthday.
“The child was treated effectively and showed no signs of illness,” Dr Michelle Farrar, a paediatric neurologist at the University of New South Wales in Sydney, Australia, who was not involved in the study, told Nature News.
SMA is an inherited disorder that affects certain motor neurons, which are the nerve cells in the spinal cord that control voluntary muscle movement. Over time, SMA eventually leads to muscle weakness and atrophy. The disorder is estimated to affect about 1 in 10,000 live births.
The disease is usually caused by mutations in the SMN1 gene, which provides instructions for making a protein called survival motor neuron (SMN) protein. This protein is critical to the function of motor neurons, allowing them to make proteins and develop the “wires” that transmit signals to muscles.
When the SMN1 gene mutates, the body is unable to produce enough SMN protein, and nerves cannot properly transmit signals to muscles. As a result, muscles — especially in the hips, back, shoulders, and buttocks — begin to weaken and shrink due to inactivity and lack of nerve stimulation.
The severity of these symptoms varies depending on the type of SMA a patient has. There are five types of SMA associated with mutations in the SMN1 gene, classified by the severity of symptoms and when they appear. Symptoms that appear earlier — before or shortly after birth — tend to result in poorer survival rates. Infants with SMA type 1, which appears within six months of birth, have severe weakness that makes breathing and swallowing difficult, and often die within the first few years of life without therapeutic intervention or respiratory support.
SMA type 1 is the leading genetic cause of childhood mortality.
The infant in the recent case was found to be at risk for SMA type 1 after genetic testing in the womb. The parents had one child with a confirmed diagnosis of SMA type 1 who had previously died. Tests showed that the developing fetus also had mutations in the SMN1 genes on both chromosomes.
The drug risdiplam (brand name: Evrysdi) is one of three treatments approved by the U.S. Food and Drug Administration (FDA) to treat SMA in infants. It is an oral pill that stimulates the body to increase the activity of a second gene, called SMN2, which also contains instructions for making the SMN protein but typically produces less of it than SMN1.
Previously, this drug was used only after birth, but in this case it was administered to the fetus in the womb at the request of the parents.
“They’ve already experienced loss to this terrible disease,” lead study author Dr. Richard Finkel, a clinical neuroscientist at St. Jude Children’s Research Hospital in Memphis, Tennessee, told Nature News. Risdiplam is approved for children over 2 months old, so the FDA gave it a special approval for early use.
At 32 weeks pregnant, the mother began taking risdiplam daily for six weeks. Testing during labor showed that the drug had indeed entered the baby's system while he was
Sourse: www.livescience.com
