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Harrison's Principles of Internal Medicine, 18e
| Part 17. Neurologic Disorders > Section 3. Nerve and Muscle Disorders > |
Chapter 387. Muscular Dystrophies and Other Muscle Diseases
Sections: Muscular Dystrophies and Other Muscle Diseases: Introduction, Hereditary Myopathies, Congenital Myopathies, Disorders of Muscle Energy Metabolism, Mitochondrial Myopathies, Disorders of Muscle Membrane Excitability, Endocrine and Metabolic Myopathies, Myopathies of Systemic Illness, Drug-Induced Myopathies, Further Readings.
Topics Discussed: muscular dystrophies; myopathy.
Excerpt:"Skeletal muscle diseases, or myopathies, are disorders with structural changes or functional impairment of muscle. These conditions can be differentiated from other diseases of the motor unit (e.g., lower motor neuron or neuromuscular junction pathologies) by characteristic clinical and laboratory findings.Most myopathies present with proximal, symmetric limb weakness (arms or legs) with preserved reflexes and sensation. However, asymmetric and predominantly distal weakness can be seen in some myopathies. An associated sensory loss suggests injury to peripheral nerve or the central nervous system (CNS) rather than myopathy. On occasion, disorders affecting the motor nerve cell bodies in the spinal cord (anterior horn cell disease), the neuromuscular junction, or peripheral nerves can mimic findings of myopathy.Symptoms of muscle weakness can be either intermittent or persistent. Disorders causing intermittent weakness (Fig. 387-1) include myasthenia gravis, periodic paralyses (hypokalemic, hyperkalemic, and paramyotonia congenita), and metabolic energy deficiencies of glycolysis (especially myophosphorylase deficiency), fatty acid utilization (carnitine palmitoyltransferase deficiency), and some mitochondrial myopathies...."
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