Screening Newborns for Neuromuscular Diseases Has Pros and Cons

Even when definitive treatments aren’t yet available, should certain neuromuscular diseases be added to newborn screening panels? What will that mean for parents?

Since the early 1960s, states have been screening newborns for conditions such as PKU (phenylketonuria), a metabolic abnormality that can be treated immediately with dietary measures. In the intervening years, the burgeoning science of molecular biology has greatly increased the number of available screening tests for conditions that might otherwise be missed in the newborn period.

The federal government makes recommendations for tests to include in newborn screening, but the states individually decide which tests they will include. In 2006, the American College of Medical Genetics (ACMG) recommended that in order to be included in a newborn screening program, a disorder should:

• be detectable by a reliable test 24 to 48 hours after birth;
• not ordinarily be detectable without the test; and
• benefit from early diagnosis and treatment.

These days, however, some experts advocate screening newborns for diseases that don’t quite meet these ACMG criteria.

DMD and SMA

One argument in favor of screening newborns for conditions that are not yet treatable is that if babies with certain disorders can be identified early in life (even before symptoms begin), experimental treatments can be tried earlier (with parental permission, of course) and might be more effective.

For example, in type 1 spinal muscular atrophy (SMA) — a disease that causes weakness of breathing and swallowing muscles early in infancy and often leads to death within two years — the number of functional motor neurons drops sharply after birth, meaning that a therapy must be administered early in this form of the disease. It’s possible that some experimental SMA therapies under development may be effective only if administered before symptoms begin.

Another disease that might benefit from early detection is Duchenne muscular dystrophy (DMD). Research is currently under way to investigate the use of antisense oligonucleotides, stop codon read-through and gene therapy strategies. Some experts advocate preparing now to screen infants for DMD rather than waiting until a treatment is approved. Recently, a two-tier newborn screening strategy was developed for DMD that appears feasible and cost-effective.  

Caveats and concerns about newborn screening

It’s hard to argue with providing a timely, effective treatment for a newborn baby, but until treatments are readily available, some experts warn, it’s also important to think about the potential downside of diagnosing a child before symptoms occur.

Nicole Johnson, a genetic counselor at Johns Hopkins University in Baltimore, studied the effects on parents of diagnosing DMD during the newborn period for her master’s degree thesis.

In 2001, she interviewed 12 of the 58 families who’d been through this experience during a 12-year pilot MD newborn screening program that ended in 1997. She found mixed reactions.

Although all of the parents felt that the newborn period wasn’t the appropriate time for an early diagnosis, no parent said that in retrospect they would have preferred a later, clinical diagnosis.

Some parents noted that having the diagnosis so early allowed them to adjust to it, so that by the time the child began asking his own questions, they felt prepared. Also mentioned were an appreciation of more time to make better decisions about career plans, child care options, and home renovations or purchases geared to the needs of a wheelchair user.

Some parents started their very young children on stretching exercises, swimming or chiropractic visits, with the hope of forestalling the effects of DMD. Seven of the 12 families surveyed said they’d changed their original reproductive plans based on knowing their son’s diagnosis.

But there were several concerns expressed by parents as well. Four parents described at least an initial period of feeling detached from their new baby once they got the diagnosis.

Others reported a feeling of chronic, bittersweet sorrow as they watched their child grow and develop. Each developmental milestone reached was greeted with excitement and at the same time with the knowledge that it probably wouldn’t be maintained for long.

“I grabbed the video camera when my child ran across the yard,” one parent told Johnson. “We try to cherish more moments than we would if we knew that he was healthy, which is a shame. But I think in the back of our minds, we know there are things we need to remember.”

Even foreknowledge of the risks to future children could be a double-edged sword, with some parents reporting that they felt alienated from the medical community if they didn’t subsequently use this knowledge to avoid having another affected child.

Information and support

Parents in Johnson’s study felt that two key elements were missing from their experience with early screening:

• a better informed consent process for the neuromuscular disease portion of newborn screening; and
• an improved, more supportive practice for the disclosure of results.

Parents in this study felt that the most negative aspect of their experience with newborn screening for MD was the process through which they first heard about their son’s possible diagnosis. They often didn’t recall giving their consent for MD screening. Many parents had assumed that everything their baby was being tested for would be treatable and were shocked to find out this wasn’t the case.

When they were later told that a screening test had revealed that their sons might have muscular dystrophy, an untreatable condition, they experienced this as completely “out of the blue.”

In two families, Johnson says, parents who didn’t even realize that their baby had been tested for MD were notified over the phone right before the Fourth of July weekend that a screening test for MD was positive. They had to wait several days before further information was available.

“Any future newborn screening program for MD has to take into account a thoughtful protocol for disclosing results that provides the best support to the parents,” Johnson says. “Professionals have to understand that this is unlike any other newborn screening, where treatment begins soon after diagnosis. There were unique emotional needs of the parents who were learning of their son’s MD test results.”