Multiple Sclerosis
Multiple Sclerosis Definition Chronic disease of young adults; characterized pathologically by multiple central nervous system white matter lesions. Epidemiology Age at onset: peaks at 20 to 30 years; rare before…
Myositis Ossificans
Myositis Ossificans Deposition of bone in subcutaneous tissue and along fascial planes in muscle. Probably sporadic appearance of an unidentified mutation. Primary disorder may be in connective tissue (fibrodysplasia ossificans)….
Polymyositis, Inclusion Body Myositis, and Related Myopathies
Polymyositis, Inclusion Body Myositis, and Related Myopathies Polymyositis Definition Polymyositis: acute or subacute onset; sometimes spontaneous improvement; infiltration of muscle by lymphocytes. Occurs alone or as part of systemic disease…
Dermatomyositis
Dermatomyositis Pathology and Pathogenesis Autoimmune disease of skin and muscle. Degeneration, regeneration, edema, infiltration by lymphocytes in both tissues. Inflammatory cells (predominantly B cells) around small vessels or in perimysium;…
Muscle Cramps and Stiffness
Muscle Cramps and Stiffness Stiffness: continuous muscle contraction at rest. Cramps (spasms): transient, painful, involuntary contraction of muscle or group of muscles; lasts seconds to minutes. Causes listed in Table…
Myoglobinuria
Myoglobinuria Acute muscle necrosis leads to gross pigmenturia (brown) with myoglobin in urine. Also termed rhabdomyolysis. Most important syndromes in Table 129.1. Hereditary Myoglobinuria Identified Enzyme Deficiencies Genetic defect identified…
Congenital Myopathies
Congenital Myopathies Primary manifestation: delayed motor milestones. Congenital Muscular Dystrophies Congenital myotonic dystrophy, congenital muscular dystrophies: muscle destruction, replacement by fat and connective tissue on muscle biopsy. Congenital muscular dystrophies…
Familial Periodic Paralysis
Familial Periodic Paralysis Episodic bouts of limb weakness. Inherited “channelopathies” (inherited abnormalities of ion channels). Clinical features in Table 127.1. Hypokalemic Periodic Paralysis (HoPP) Serum potassium decreases in spontaneous attack…
Progressive Muscular Dystrophies
Progressive Muscular Dystrophies General Considerations Definition Characteristics of progressive muscular dystrophy: (1) myopathy (by clinical, histologic, and EMG criteria); (2) all symptoms are effects of muscle weakness; (3) symptoms become…
Identifying Disorders of the Motor Unit
Identifying Disorders of the Motor Unit Motor unit: anterior horn cell, peripheral motor nerve, muscle. Manifestations: flaccid weakness, wasting, depression of tendon reflexes (Table 125.1). Tests to distinguish neurogenic from…
