Duchenne Muscular Dystrophy is a disease of:
Correct Answer: Sarcolemmal proteins
Description: Answer is B (Sarcolemmal protein) : Duchenne muscular dystrophy is caused kr a mutation in the gene responsible few producing dystrophin. Dystrophin is `subsarcolemmal protein' (Nelson) localized to the inner surface of the sarcolemma of the muscle fibre. Harrison 17th/2683 Dystrophin is pa of Dystrophin - Glycoprotein sarcolemmal complex and this protein deficiency leads to secondary loss of sarcoglycans and dystroglycans resulting in weakness of sarcolemma, causing membrane tears and muscle fibre necrosis Duchenne muscular dystrophy: Review (pseudohyperophic muscular dystrophy) Duchenne muscular dystrophy is the most common hereditary neuromuscular disease affecting all races and ethnic groups. Inheritance : X linked recessive Presentation occurs between ages 3 and 5 Clinical manifestations: Gower's sign is positivedeg Pseudohyperophy of calf is seendeg (muscle is replaced by fat & connective tissue) Loss of muscle strength is progressive. 2 Proximal muscles and neck flexors are involved more. 2 Leg involvement is more severe than arm involvement. Contractures of heel cords and iliotibial band occurs (by age of 6 years) Progressive scoliosis develops. Complications: Chest deformityQ (scoliosis) : Impairs pulmonary functiondeg By age of 16 and 18 years patients are predisposed to serious pulmonary fatal infections. Cardiac: Cardiomyopathy and CHF may be seen Cardiac cause of death is uncommon Intellectual impairment : is commondeg (IQ is one SD below the mean) Remember: Onset 2 Before age of 5 2 Confined to wheel chair Inability to walk After age of 12 e Respiratory failure In second or third decade (after 16-18 years)2 Laboratory diagnosis: Serum creatinephosphokinase (CK)Q : elevated (20-.100 times) EMG : features of myopathy Muscle biopsyQ : - Definitive diagnosis established on basis of dystrophin deficiency in biopsied muscle tissue - Groups of necrotic and regenerating muscle fibres are seen. Treatment: - Glucocoicoids (Prednisolone) have been tried. - Significant alteration in the progression of disease has been seen with prednisolone.
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