A 12 year old boy presented with progressive muscular weakness showing the following finding, and it was found that the child is unable to get up from squatting position. He was diagnosed with hereditary muscular disorder. What is the mode of inheritance in this disorder?

The given picture shows pseudohyperophy of calf muscles, also the child is unable to get up from squatting position. This is characteristically seen in Duchenne muscular dystrophy, which is an X-linked recessive disorder. Salient features of Duchenne muscular dystrophy: Most common hereditary neuromuscular disease X-linked recessive deletion of dystrophin gene on Chromosome Xp21 Clinical Features: Progressive weakness, developmental delay, and intellectual impairement In toddlers: delayed walking, falling, toe walking, and trouble running or walking upstairs Common sites of muscular hyperophy: Calf>tongue>forearm Gower&;s Sign: Patient has to use their hands and arms to walk up their own body from squatting position due to lack of hip and thigh muscle strength due to weakness of proximal muscles, especially of the lower limbs. Tredelenburg gait/hip waddle Complications: Contractures, scoliosis, cardiomyopathy, malignant hypehermia after anesthesia Patient is unable to walk by the age of 12 years and death occurs by 18-20 years of age, due to respiratory failure. Note: Becker&;s Muscular Dystrophy (BMD) vs Duchenne Muscular Dystrophy(DMD) Ref: Nelson textbook of pediatrics 21st edition pgno: 3281