Pathophysiology

Pathophysiology Study Guide

©2018 of 131 Muscular Dystrophy Muscular dystrophy is the group of diseases that lead to progressive weakness in muscles and loss of muscular mass. This disorder is characterized by the interference of mutated genes with the protein production in the body, which effects the formation of healthy muscles. There is no cure for muscular dystrophy but medicines can help relieve symptoms of the disorder. The main cause of muscular dystrophy is the inheritance of mutated genes. The main sign of this disorder is progressive weakness in the muscles. There are different types of muscular dystrophy: Duchenne muscular dystrophy, Becker muscular dystrophy, and others. Signs and symptoms are visible mostly between two to three years of age and include frequent falls; difficulty getting up, lying down, and sitting properly; difficulty in running and jumping; waddling gait; walking on toes; large calf muscles; pain and stiffness in the muscles; and learning disabilities. The symptoms of Becker muscular dystrophy are visible only after adolescence and are similar but milder than Duchenne muscular dystrophy. Other muscular dystrophies are myotonic (symptoms: inability to relax muscles); facioscapulohumeral (symptoms: weakness in the face and shoulders); congenital; and limb-girdle (symptoms: weakness in hip and shoulder muscles). Myopathies Myopathy refers to a disorder involving skeletal muscle weakness and dysfunction, characterized by the abnormal structure of the muscles cells and abnormal metabolism. Myopathies can be acquired or inherited. In the former case, the disorder becomes visible suddenly with a sub-acute presentation at a later stage, while the latter is characterized by an early onset of the disorder with a longer duration of the disease. Inherited myopathies are further categorized as muscular dystrophies, congenital myopathies, mitochondrial myopathies, and metabolic myopathies. In contrast, the acquired myopathies are classified as inflammatory myopathies, toxic myopathies, and systemic conditions associated myopathies. The causes of inflammatory acquired myopathy include pilymyositis, dermatomyositis, and inclusion body myositis. Viral infections (HIV, influenza virus, and Epstein- Barr virus), bacterial pyomyositis, and spirochete and parasitic infections are the common causes for infection based myopathies. Medications like steroids, cholesterol lowering medicines, propofol, tryptophan, and toxins like alcohol and toluene are causes for toxic myopathy. Causes for systemic diseases are endocrine disorders, systemic inflammatory diseases, electrolyte imbalance, critical illness myopathy, and amyloid myopathy. Causes of macular dystrophy (inherited) are dystrophinopathy, myotonic dystrophy 1 and 2, facioscapulohumeral muscular dystrophy, oculopharyngeal muscular dystrophy, and limb girdle muscular dystrophy. Congenital myopathy is caused by nemaline and central core myopathy. Metabolic myopathy is due to acid maltase, Pompe's disease, glycogen storage disorders, carnitine deficiency, fatty acid oxidation defects, and carnitine palmitoyl transferase deficiency. Finally, mitochondrial myopathy is caused by myoclonic epilepsy and ragged red fibers, mitochondrial myopathy, lactic acidosis and strokes, mitochondrial neurogastrointestinal encephalomyopathy, and progressive external ophthalmoplegia. Achieve Page 103