Prenatal and Pregnancy Examinations for Spinal Muscular Atrophy
Spinal Muscular Atrophy (SMA) is a genetic condition that affects motor neurons in the spinal cord, leading to muscle weakness, difficulty controlling movements, swallowing, and breathing. Around 1 in 40 to 1 in 60 people have the SMN1 gene mutation associated with SMA [1].
The SMN protein is crucial for motor neurons to function properly, and it is produced by the SMN1 and SMN2 genes. People with SMA have at least one copy of the SMN2 gene, and some people have multiple copies. One treatment for SMA targets the SMN2 gene to increase SMN protein production, such as the disease-modifying medication Nusinersen [2]. For more significant SMN protein production, there is gene replacement therapy, such as onasemnogene abeparvovec [2].
Prenatal testing options for SMA include carrier screening, molecular genetic testing of the fetus, and noninvasive prenatal testing (NIPT). Carrier screening is recommended for all individuals considering pregnancy or who are currently pregnant to identify carriers of SMA mutations. If a carrier is identified, testing is recommended for the reproductive partner to evaluate the risk of having an affected child [1].
Molecular genetic tests, such as the SALSA MLPA Probemix P021 SMA, can detect deletions or duplications in the SMN1 gene responsible for SMA, typically using blood samples [1]. Newer noninvasive tests analyze maternal blood to screen for fetal risk of SMA and other single-gene disorders with high accuracy, identifying homozygous mutations that cause the condition [3].
Factors determining when to consider SMA testing include planning pregnancy or early pregnancy, family history of SMA or related symptoms, known carrier status in one partner, prenatal ultrasound findings suggesting possible SMA or other genetic abnormalities, and population-based screening recommendations [1].
Early identification through screening supports prompt diagnosis and early initiation of therapies shown to improve outcomes in affected infants [4]. Carrier screening is generally done once, although repeat testing may be considered under expert guidance due to evolving test panels [1]. The integration of SMA testing into newborn screening and premarital programs has also been advocated to improve early diagnosis and intervention [5].
If both partners carry the SMA gene mutation, their children have a high chance of developing SMA. In the United States, 39 states perform SMA blood testing as a routine part of newborn screening [6]. If a newborn or infant tests positive for SMA, they may receive treatments like nusinersen or gene replacement therapy.
People who carry the SMA gene mutation but do not have the disease will pass a copy of the mutated SMN1 gene to all of their offspring, making them carriers. If a person carries the SMA gene mutation, they may consider options such as prenatal testing, testing an embryo, intrauterine insemination with donor sperm, surrogacy, or adoption to prevent passing the mutation to their children [1].
Prenatal testing can be done using amniotic fluid or placenta samples to check for abnormal SMN genes. Prenatal SMA testing is crucial for families to make informed decisions about their reproductive choices and to prepare for potential interventions for affected children.
References: [1] National Institute of Neurological Disorders and Stroke. (2021). Spinal Muscular Atrophy Fact Sheet. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Spinal-Muscular-Atrophy-Fact-Sheet [2] National Institute of Neurological Disorders and Stroke. (2021). Spinal Muscular Atrophy: Hope Through Research. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Spinal-Muscular-Atrophy-Hope-Through-Research [3] American College of Medical Genetics and Genomics. (2021). Carrier Screening for Spinal Muscular Atrophy. https://www.acmg.net/ACMG/Pages/FamilialDisease/SpinalMuscularAtrophy.aspx [4] National Center for Biotechnology Information. (2021). Spinal Muscular Atrophy. https://ghr.nlm.nih.gov/condition/spinal-muscular-atrophy [5] National Institute of Child Health and Human Development. (2021). Newborn Screening. https://www.nichd.nih.gov/health/topics/newbornscreening [6] Genetic and Rare Diseases Information Center. (2021). Spinal Muscular Atrophy. https://rarediseases.info.nih.gov/diseases/7297/spinal-muscular-atrophy
Read also:
- Foods to avoid for someone with interstitial cystitis include acidic foods like citrus fruits, spicy foods, artificial sweeteners, caffeine, alcohol, and fast foods high in sodium and preservatives.
- Analysis of Ro Hair Loss Solution: Is it the Optimal Choice for Male Pattern Baldness?
- Gatherings for Managing Eczema Symptoms
- Delhi sees city-wide canine capture following judicial order by Indian court
