Cystic fibrosis and spinal muscular atrophy: How genetic testing can change the game for two serious inherited conditions¹

Inherited conditions are health conditions a parent might pass on to a child through their genes. Yet most babies with genetic conditions are born to parents with no known family history of that disease.² That’s because it’s possible for parents to be carriers of a condition without having any symptoms.

With many genetic conditions, there’s a 25% chance a baby will inherit the genetic changes and develop symptoms if both parents have a change in the same gene, i.e. if they are both carriers. These types of conditions, called autosomal recessive conditions, affect up to one in 200 pregnancies.³

Two serious inherited conditions

Two common inherited conditions are cystic fibrosis (CF) and spinal muscular atrophy (SMA).

CF is one of the most common inherited diseases in people of European descent, impacting approximately one in 3,000 births.⁴ However, people of all ethnic backgrounds can still be at risk for CF. It is caused by having at least two genetic changes to the CFTR gene – one from each parent.

CF is characterized by thick, sticky mucus, particularly in the lungs and digestive system, though CF affects many organs. It can cause chronic breathing problems and lung infections, and people with CF have a shortened life expectancy. ⁵

There are now multiple FDA-approved treatments and targeted therapies for CF, as well as several options for treating symptoms associated with CF, which include addressing nutritional deficits or taking vitamin supplements, antibiotics, or anti-inflammatory agents. Also, new therapies are emerging that aim to target CF before symptoms start.

With a growing number of treatments and interventions, a theme from CF research is the importance of early detection and diagnosis so treatment can begin as soon as possible.⁶

While individuals with CF have shortened lifespans, new treatments and early intervention have improved the life expectancy for individuals with CF to 50 or even 60 years.⁵

The other serious inherited condition, SMA, causes loss of motor neurons that control movement. In severe cases, an affected person cannot sit independently, and their breathing and swallowing may be impaired.⁷ In mild cases, symptoms begin in adulthood and independent movement becomes more difficult.

Up to one in 40 people are carriers of SMA and it affects approximately one in 10,000 live births.¹ It is the most common inherited cause of infant mortality.⁸  

Right now, there is no cure for SMA. However, the approval of three disease-modifying therapies since 2016 has greatly improved quality of life and life expectancy for patients with SMA.⁹

As with CF, early diagnosis, treatment, and intervention improve the outcomes for patients with SMA.¹⁰ (See the Pantier family’s story here.) One study found that even children who would have been expected to develop a severe form of SMA had profoundly improved motor development, provided they started disease-modifying therapy immediately after diagnosis.¹⁰

Carrier screening for CF and SMA

Carrier screening is a non-invasive test that can be done either before or during pregnancy. The screening can include CF, SMA, and other genetic conditions. It requires just a small amount of saliva or blood, and you normally have the results in about two weeks. In most cases, this simple screening will provide reassuring results that you are at low risk of passing on an inherited condition to your child.

The American College of Obstetricians and Gynecologists and the American College of Medical Genetics and Genomics recommend that carrier screening be offered to every patientwho is pregnant or who is considering pregnancy.^{11, 12}

If you are not yet pregnant, your screening results can help you determine if you might want to consider in-vitro fertilization with additional screening of embryos for genetic conditions before implantation. Other options you may consider include adoption or sperm/egg donation.

If you and your partner screen during pregnancy and you find out your baby is at increased risk for CF or SMA, a next step may be a prenatal diagnostic test, like amniocentesis or chorionic villus sampling. These tests will determine if the inherited condition was passed on to your child.

If the genetic condition is passed on, your preparations are extremely important. You may want to identify specialists and seek additional support so you have a care team in place to provide the most effective treatment for your child at birth.  

Inherited genetic conditions like CF and SMA are relatively rare. But if your baby has one of these conditions, it can be beneficial to know it as early as possible. Being prepared in advance and learning about available treatments and interventions may help to improve your baby’s health in the long run.

REFERENCES

1. Prior, T., for the Professional Practice and Guidelines Committee. Carrier screening for spinal muscular atrophy. Genet Med 10, 840–842 (2008). https://doi.org/10.1097/GIM.0b013e318188d069
2. Morris JK, Law MR, Wald NJ. Is cascade testing a sensible method of screening a population for autosomal recessive disorders?. Am J Med Genet A. 2004;128A(3):271-275. doi:10.1002/ajmg.a.30024
3. Xiao, Q., Lauschke, V.M. The prevalence, genetic complexity and population-specific founder effects of human autosomal recessive disorders. npj Genom. Med. 6, 41 (2021). https://doi.org/10.1038/s41525-021-00203-x
4. Michelson P, Faro A, Ferkol T. Pulmonary disease in cystic fibrosis. In: Wilmott R, Bush A, Ratjen F, et al. ed. Kendig’s Disorders of the Respiratory Tract in Children. 9th ed. Philadelphia, PA: Elsevier Health Sciences; 2018:777–87. 
5. Cleveland Clinic. Cystic fibrosis. https://my.clevelandclinic.org/health/diseases/9358-cystic-fibrosis. Accessed April 9, 2025.
6. Coverstone A, Ferkol T. Early diagnosis and intervention in cystic fibrosis: imagining the unimaginable. Frontiers in Pediatrics 2021;8:608821. doi: 10.3389/fped.2020.608821.
7. Cleveland Clinic. Spinal muscular atrophy. https://my.clevelandclinic.org/health/diseases/14505-spinal-muscular-atrophy-sma. Accessed April 9, 2025.
8. Kolb SJ, Kissel JT. Spinal Muscular Atrophy. Neurol Clin. 2015 Nov; 33(4): 831–846. doi:
9. 1016/j.ncl.2015.07.004 9. Flinn, Ryan. Early screening and treatment for spinal muscular atrophy in newborns significantly improves outcomes. Managed Healthcare Executive, July 5, 2024.
10. Flinn, Ryan. Early screening and treatment for spinal muscular atrophy in newborns significantly improves outcomes. Managed Healthcare Executive, July 5, 2024. https://www.managedhealthcareexecutive.com/view/early-screening-and-treatment-for-spinal-muscular-atrophy-in-newborns-significantly-improves-outcomes. Accessed April 22, 2025.
11. Schwartz O, Vill K. Clinical effectiveness of newborn screening for spinal muscular atrophy. JAMA Pediatr. 2024;178(6):540-547. doi:10.1001/jamapediatrics.2024.0492. 
12. American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins—Obstetrics; Committee on Genetics; Society for Maternal-Fetal Medicine. Screening for fetal chromosomal abnormalities: ACOG Practice Bulletin, Number 226. Obstet Gynecol. 2020;136(4):e48-e69. doi:10.1097/AOG.0000000000004084.
13. Gregg AR, Aarabi M, Klugman S, et al. Screening for autosomal recessive and X-linked conditions during pregnancy and preconception: a practice resource of the American College of Medical Genetics and Genomics (ACMG). Genetics in Medicine 2021;23 1793–1806 (2021). https://doi.org/10.1038/s41436-021-01203-z.