What is the role of lab testing in the workup of spinal muscle atrophy (SMA)?

Updated: Nov 05, 2018
  • Author: Ashish S Ranade, MBBS, MS, MRCS; Chief Editor: Jeffrey A Goldstein, MD  more...
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Answer

A simple blood test can confirm whether the child has a mutation that causes spinal muscle atrophy (SMA; also known as spinal muscular atrophy). If the survival motor neuron (SMN) gene test is positive, the diagnosis is confirmed. However, 5% of children with the symptoms of SMA can have a negative SMN gene test and may require additional diagnostic testing. These tests can include electromyography (EMG), a nerve conduction study (NCS), or muscle biopsy and additional blood tests to help rule out other forms of muscle disease.

In contrast to findings in patients with Duchenne muscular dystrophy and Becker muscular dystrophy, aldolase and serum creatine kinase (CK) findings are within reference ranges in patients with SMA. In later-onset SMA, these muscle enzymes may be slightly elevated.


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