Chapter 9 Skeletal muscle disorders

Abstract

This chapter discusses the muscular dystrophies; the congenital myopathies; the metabolic myopathies; the myotonias, periodic paralyses, and malignant hyperpyrexia; the neurogenic disorders; the inflammatory muscle disorders; the endocrine myopathies; and the drug-induced and toxic myopathies. Each of these disorders comprises a description of the clinical aspects followed by discussions of genetics, histopathology, biochemistry, and pathophysiology. The first step in the management of muscle disease is achieving a completely accurate diagnosis, where an iatrogenic or primary condition may be identified, then removal or cure of the primary condition is an obvious part of the management and may be very successful in relieving the problem. Drug treatment may be appropriate in the management of inflammatory myopathies, and steroids and immunosuppressants are used with varying success in their management. Supplementation with carnitine or other cofactors in the respiratory chain may be used in various metabolic muscle diseases. The drugs of choice in myasthenia gravis are the anticholinesterases, sometimes with the addition of steroids and immunosuppressants. Thymectomy and plasmapharesis are other treatment options in this condition. However, the overall role of drugs or other specific therapeutic measures in the treatment of muscle disease is limited. Among the disorders discussed in the chapter, many are inherited and progressive, lead to significant disability, and no specific treatment is available. The management of these conditions very much depends on a holistic and multidisciplinary approach.