Fast Five Quiz: Spinal Muscular Atrophy in Adults

Stephen L. Nelson, Jr, MD, PhD


February 01, 2021

The differential diagnosis for adult-onset SMA includes amyotrophic lateral sclerosis and Kennedy disease, and other disorders of the peripheral nervous system including myopathy (dystrophinopathies, limb girdle muscular dystrophy, metabolic myopathies, or inflammatory myopathies), neuropathy (inflammatory neuropathies), neuromuscular junction disorders (myasthenia gravis or congenital myasthenic syndromes), and other motor neuron disorders (non-5q form of SMA or late-onset hexosaminidase A deficiency).

Before molecular testing became available, diagnostic studies to demonstrate the presence of denervation, such as electrodiagnostic studies and muscle biopsy, were important tools for evaluating suspected SMA. Typically, electrodiagnosis is now reserved only for evaluation of atypical patients or patients who are negative for both SMN1 deletion and SMN1 mutation testing. Muscle biopsy is no longer indicated because electrodiagnosis can more easily demonstrate features of denervation.

Learn more about the workup for SMA.


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.