Fast Five Quiz: Can You Diagnose the Different Types of Spinal Muscular Atrophy?

Stephen L. Nelson, Jr, MD, PhD

December 06, 2018

Genetic testing is the most efficient and reliable method to test for SMA. Homozygous SMN1 gene deletion is 100% specific and 95% sensitive for SMA.

For patients in whom SMA is still suspected despite the absence of homozygous deletion of SMN1, further sequencing of any present SMN1 copies is recommended. If genetic testing proves unrewarding, further laboratory evaluation is required.

Prenatal ultrasound for SMA does not usually reveal significant abnormalities. Chorionic villi sampling and amniocentesis are relatively accurate in detecting SMA; however, clinicians should be wary of diagnosis through these methods alone when any atypical features are present. Because CSF analyses are normal in patients with SMA, it is not an appropriate diagnostic test for the SMA. Radiography can be valuable if genetic testing is unrewarding, but findings may be nonspecific to SMA.

Differential diagnoses to consider include:

Congenital muscular dystrophy
Congenital myopathies
Primary lateral sclerosis
Amyotrophic lateral sclerosis
Disorders of carbohydrate metabolism
Myasthenia gravis

For more on diagnostic testing for SMA, read here.

1 2 3 4 5 6

Next Section

Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.

Cite this: Stephen L. Nelson. Fast Five Quiz: Can You Diagnose the Different Types of Spinal Muscular Atrophy? - Medscape - Dec 06, 2018.

Comments

Commenting is limited to medical professionals. To comment please Log-in.

Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.