Clinical diagnosis and genetic analysis of a rare case of Duchenne muscular dystrophy and spinal muscular atrophy.

objectiveTo explore the clinical and genetic features both spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD) diagnosed in a child.

methodsA child was diagnosed with SMA combined with a duplication of exons 2-20 in the DMD gene at another hospital. Optical genome mapping (OGM) was employed to assess whether the duplication of exons 2-20 in the DMD gene affected its function.

resultsThe patient was a 19-month-old boy who presented with delayed motor development and generalised hypotonia. Whole exome sequencing (WES) and multiplex ligation-dependent probe amplification (MLPA) performed at another hospital indicated that the patient had a hemizygous duplication involving exons 2-20 of the DMD gene, which was maternally inherited. Additionally, the patient had a homozygous deletion of SMN1 exons 7 and 8 (zero copies) and 3 copies of SMN2 exons 7 and 8. Both parents carried one copy of SMN1. Additionally, the mother harboured two copies of SMN2, whereas the father had three copies of SMN2. OGM analysis revealed a tandem duplication of exons 2-20 in the DMD gene in the patient and his mother.

conclusionWe describe a rare case of a patient with concomitant DMD and SMA. When a patient's phenotype cannot be explained by a single genetic disorder, the possibility of multiple genetic disorders coexisting due to multiple mutations must be considered. OGM is a valuable diagnostic tool for determining the pathogenicity of DMD exon duplications, as it can definitively establish their genomic location and structure.