FMR1 and fragile X syndrome: Furthermore, some certain genes of high clinical importance are technically challenging to assess with NGS because of pseudogenes, CGG repeat expansions, or DNA structural variations (e.g., survival of motor neuron 1 (SMN1) [MIM *600354] for spinal muscular atrophy (SMA) and fragile X mental retardation 1 (FMR1) [MIM *309550] for fragile X syndrome)13.