Spinal muscular atrophy (SMA) is a genetic disorder that affects the control of muscle movement. It is caused by a loss of specialized nerve cells, called motor neurons, in the spinal cord and the brainstem. The loss of motor neurons leads to weakness and wasting of muscles used for activities such as crawling, walking, sitting up, and controlling head movement. In severe cases of spinal muscular atrophy, the muscles used for breathing and swallowing are affected. The many subtypes of spinal muscular atrophy are distinguished by the pattern of features, severity of muscle weakness, and age when the muscle problems begin.

SMA is an autosomal recessive disease caused by a genetic defect in the SMN1 gene. The SMN1 and SMN2 genes provide instructions for making a protein called the survival motor neuron (SMN) protein. The SMN protein is important for the maintenance of motor neurons. SMN1 gene mutations lead to a shortage of the SMN protein. Without SMN protein, motor neurons die, and nerve impulses are not passed between the brain and muscles. As a result, some muscles cannot perform their normal functions, leading to weakness and impaired movement.

Most individuals with spinal muscular atrophy have mutations in both copies of the SMN1 gene. As a result, little or no SMN protein is produced from this gene. The SMN2 gene can help replace some of the missing SMN protein. In people with spinal muscular atrophy, having multiple copies of the SMN2 gene is usually associated with less severe features of the condition that develop later in life. Affected individuals with one or two functional copies of the SMN2 gene generally have severe muscle weakness that begins at birth or in infancy. Affected individuals with four or more copies of the SMN2 gene typically have mild muscle weakness that may not become noticeable until adulthood. Other factors, many unknown, also contribute to the variable severity of spinal muscular atrophy.

This assay employes PCR and copy number detection of the SMN1 and SMN2 genes at exon 7.

CPT Code: 81329

Specimen Requirements: 2-5 mL Blood- EDTA tube (Lavender Top)

For Buccal Swab or Saliva samples please contact the lab to obtain a collection kit.

Turn-around-time: 21 days

Disease Specific DNA Test Order Form






Contact Information

OUHSC Genetics Laboratory 1122 NE 13th Street, Suite 1400, Oklahoma City, OK 73104

Phone (405)271-3589 Fax (405)271-7117 After hours phone (405)496-9514


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