A DMD case caused by X chromosome rearrangement.

Duchenne/Becker muscular dystrophy (DMD/BMD) is one of the most common progressive muscular dystrophy diseases with X-linked recessive inheritance. It is mainly caused by the deletion, duplication and point mutation of DMD gene. In rare cases, it is also caused by the destruction of DMD gene by chromosomal structural rearrangement. Here, we report a case of Duchenne/Becker Muscular dystrophy (DMD/BMD) with typical symptoms but unknown genetic defects after MLPA and next generation sequencing tests in other hospitals. Interestingly, we find a pericentric inversion of X chromosome (Chr.X: g. [31939463-31939465del; 31939466-131765063 inv; 131765064-131765067del]) in this patient. We then use the karyotyping, FISH, long-read sequencing and Sanger sequencing technologies to characterize the chromosome rearrangement. We find that this chromosomal aberration disrupt both the DMD gene and the HS6ST2 gene. The patient present with typical DMD symptoms such as muscle weakness, but no obvious symptoms of Paganini-Miozzo syndrome. Our results suggest that the destruction of DMD gene by structural rearrangement is also one of the important causes of DMD. Therefore, we suggest to provide further genetic testing for those DMD patients with unknown genetic defects through routine genetic testing. Cost-effective karyotyping and FISH should be considered firstly to identify chromosome rearrangements. Long-read sequencing followed by Sanger sequencing could be useful to locate the precise breakpoints. The genetic diagnosis of this case made it possible for reproductive intervention in the patient's family.