Microarray recommendations for DMD and SMA

Microarray analysis  has a wide range of applications in Pediatrics, Neonatology and Genetics.

One of of the commonly asked questions by clinicians is
“Which type of array will be useful to pick up exon deletions and duplications. For eg. in case of Duchenne Muscular Dystrophy (DMD) or Spinal Muscular Atrophy (SMA).”

All the arrays (high or low density) will detect deletions (dels) and duplications (dups). The higher density array (HD) will be able to pick up smaller dels/dups that may be missed by other lower resolution arrays (LD and ULD).

However it is difficult to predict whether a patient will have a smaller del/dup or bigger. So we always recommend HD if the patient can afford. If not, an LD or a ULD.

For SMA, microarray testing is not recommended because it is a very small gene and a very small exonic change may not be detected by arrays. There is a specific assay designed for this gene.

For DMD, 60% patients have del/dup which will be picked up by array. Remaining 40% have a mutation in the DMD which can be detected by sequencing. At the same time, sequencing will not detect deletion/duplication. Hence it is advisable to first order a microarray and if the array results are negative then order a sequencing test.