MISSED BY OTHERS, DETECTED BY US
Genomic Unity® Case Study

Deep intronic variant explains progressive myopathy

Clinical presentation

A 19-year-old male presented with a history, shared with his brother, of slowly progressive myopathy with notable humeral and peroneal weakness:

  • 7 years old – Myopathy first evident
  • 11 years old – Muscle biopsy identified severe dystrophic changes suggestive of dystrophinopathy
  • 15 years old – Wheelchair dependent

Previous genetic testing

Multiple tests were performed with negative results including:

  • SNP microarray
  • Limb girdle panel
  • Whole exome sequencing

Genomic Unity® Testing

was ordered because of its ability to identify all major variant types in a single test.

Results and interpretation

Variantyx Genomic Unity® testing identified a deep intronic, hemizygous, likely pathogenic variant in the DMD gene that causes retention of an intronic segment.

His symptomatic brother shares the same variant.

Diagnosis: Duchenne muscular dystrophy

IGV view of DMD intronic variant

Uniform data from WGS (top) clearly shows the deep intronic variant. The variant is undetectable by exome testing (bottom) due to coverage gaps.

The Variantyx Difference

Why was this deep intronic variant detected by Genomic Unity® testing, and not detected by other tests?

  • Single nucleotide changes are below the limit of detection (50-100 kb) of SNP microarray tests.
    Variantyx genome analysis has a detection range from 1 bp to whole chromosomal events.

  • The variant is deep within an intron, making it undetectable by most available technologies – including panel and exome tests.
    Variantyx genome analysis includes intronic regions, enabling variant detection regardless of location.

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