Duchenne/Becker Muscular Dystrophy Carrier Screening

This test is designed to detect carriers of Duchenne and Becker muscular dystrophy. Duchene muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive disorders characterized by progressive muscle weakness and atrophy affecting skeletal muscles and the heart. DMD usually presents in males before the age of 5 and symptoms include difficulty running, climbing, and getting up from the floor. DMD progresses rapidly with wheelchair dependency by the age of 12 and death due to respiratory complications or dilated cardiomyopathy typically before the age of 30. BMD is a less severe disorder with later onset and slower progression. Males with BMD remain ambulatory beyond the age of 16 and typically live into their 40s with dilated cardiomyopathy the most common cause of death. Some males show little or no evidence of skeletal muscle disease but present with dilated cardiomyopathy, usually in their 20s to 40s. Targeted therapies may be available for some affected individuals and will likely improve the clinical course of these disorders. DMD (MIM 310200), BMD (MIM 300376), and DMD-associated dilated cardiomyopathy (MIM 302045) are caused by pathogenic variants in the DMD gene (NM_004006). The most common pathogenic variants in DMD are large deletions and duplications encompassing one or more exons of the gene. Females with a heterozygous pathogenic variant in DMD are carriers for a DMD-associated disorder. Male children of a female carrier have a 50% chance of being affected with the disorder. Female children of a female carrier have a 50% chance of being a carrier of the disorder. Additionally, females with a heterozygous pathogenic DMD variant may develop symptoms of these disorders, including muscle weakness and dilated cardiomyopathy. Pathogenic variants in DMD have a high incidence of de novo occurrence and germline mosaicism; therefore, individuals with a negative carrier screen may still be at risk for having a child with a DMD-associated disorder. This test is intended for pre/post-conception carrier screening and is not intended for diagnostic testing.