A - 45 Duchenne and Becker Muscular Dystrophy: Sibling Case Studies

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Abstract Objective Duchenne Muscular Dystrophy (DMD) is an X-linked recessive neuromuscular condition primarily affecting males. Progressive proximal muscle wasting and weakness is seen and a shortened life span can occur due to cardiac involvement. Becker Muscular Dystrophy (BMD) is a milder form of DMD. Non-progressive cognitive impairment (e.g., lower IQ) in DMD has been well established, while the cognitive profile in BMD is less known. DMD/BMD are caused by mutations in the dystrophin protein. Research suggests that mutations downstream of exon 63 in the DMD gene are associated with poorer cognitive outcomes compared to upstream 1–30. Our cases explore the association between genetic/medical factors upon cognitive and behavioral outcomes, and neuropsychological similarities/differences between DMD and BMD. Method The current sibling case studies include one BMD set (mutations at exon 45–49) and two DMD sets (exon 61–74, and 13, respectively). They are part of a larger IRB-approved research dataset. Notably in DMD set two, the siblings have different biological fathers. Results The BMD siblings have comparable neuropsychological profiles (e.g., below average IQ, academic challenges, attention/executive problems). In DMD set one, one sibling has average intelligence with no academic challenges, while the other sibling has a low average IQ with challenges in math and spelling. In DMD set two, one sibling has intact cognitive functioning, while the other sibling performs well below average across neurocognitive domains. Conclusions Our results indicate variabilities in DMD/BMD, highlighting the contributing role of established factors (e.g., mutation location) and additional non-DMD influences (e.g., genetic contributions from biological father) to understand neuropsychological profiles.

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