Any child or adult with suspected SMA will be physically examined. This may be by their GP, paediatrician, neurologist or neurological specialist who will ask about their medical history and concerns. A GP may have met few children or adults with SMA so may make an immediate referral to a specialist neuromuscular centre. Once SMA is suspected, a blood sample for DNA testing will be arranged. The blood sample is tested for a deletion mutation in the Survival Motor Neuron 1 (SMN1) gene on chromosome 5. It is also now recommended that the number of SMN2 copies is also assessed as this can be a helpful indicator of what effects the condition will have. Clinical trials of new treatments often have entry criteria that specify the number of SMN2 copies someone must have to be eligible to take part.
The SMN1 deletion test result is usually available within 2 – 4 weeks. Other tests may take longer.
If there’s any uncertainty about the diagnosis, further tests such as an electromyogram (EMG) which records the electrical activity of muscles may be discussed, but this isn’t usually needed to confirm 5q SMA.