Muscles in the body consist of both voluntary and involuntary forms and of these voluntary or sthated muscles constitute the largest component in the body. A muscle is composed of several muscle fibres and each muscle fibre represents a separate anatomic and physiologic unit.
A single muscle fibre contains thousands of myofibrilis which are bathed in an intracellular fluid called sarcoplasm, which contains various subcellular structures such as glycogen granules, mitochondria lipofuscin etc. Connective tissue invests the muscle fibers. The integrity of muscle shall depend on the adequate blood supply and intact nerve connection.
Any disease which involves any constituent of muscle shall result in its disorders.
Thus there may be inflammatory disorders of muscles (Polymyositis, dermatomyositis) congenital myopathies, genetically determined degenerative myopathy (duchenne type, becker type, Fascio seapulo humeral, limb girdle myopathy etc) and muscle disorders associated with endocrine and metabolic disorders (Thyrotoxic myopathy pituitary, adrenal disorder osteomalacia, nutritional myopathy).
Classification of muscle disorders
1. lnflamamtory
(a) Dermatomyositis
(b) Poly myositis
2. Muscular dystrophies
(a) X-linked Severe (Duchenne)
Mild (Becker Type)
(b) Autosomal recessive muscular dystrophy Limb gridle (Scapulohumeral)
Congenital muscular dystrophy
(c) Autosomal dominant muscular dystrophy
Facioscapulo humeral
Late onset proximal limb gridle / Distal myopathy
Ocular muscular dystrophy
3. Myotonic disorders associated with myopathy. Myotonia congenita (Thomson’s disease) Dystrophia myotonica
4. Lipid and glycogen storage myopathies
5. Familial periodic paralysis
6. Endocrine myopathy (Thyroid, pituitary, adrenal and para thyroid disorders), steroid myopathy.
7. Metabolic myopathies: Osteomalacia, nutritional myopathy.
