274 14 Diseases of Muscle (Myopathies)

	Table 14.7 Infectious and inflammatory myopathies (myositi-		pain, and sometimes even fever. Thereafter, a usually
	des)		symmetrical, mainly proximal muscle weakness
	Autoimmune inflam-	dermatomyositis and polymyositis in	develops. Patients have difficulty rising from a squatting
			position, getting up from a chair, or raising the arms
	matory disorders	adults
	mainly affecting	dermatomyositis and polymyositis in	above the horizontal position. The muscles are often
	muscle	children	tender to pressure. The symptoms and signs progress
		dermatomyositis and polymyositis ac-	rapidly over a few weeks or months. About one-third of
		companying malignancy	patients suffer	from dysphagia, which may result in
		inclusion body myositis	aspiration pneumonia. If the skin is involved as well
		myofasciitis with macrophages
			(dermatomyositis), it is discolored to a reddish-purple
	Autoimmune	scleroderma
			hue. The discoloration may involve the face in “but-
	inflammatory	Sjögren syndrome	terfly” fashion (nose and both cheeks), or it may be vis-
	disorders affecting	systemic lupus erythematosus
			ible on the chest, on the dorsum of the hand, or around
	muscle as well as	rheumatoid arthritis
			the fingernails. Subcutaneous calcinosis, joint pain, joint
	other organ systems	mixed collagenosis (mixed connective
		tissue disease, Sharp syndrome)	effusions (rare), and Raynaud-like phenomena may also
		periarteritis nodosa	be present. The heart may be involved (extrasystole,
		Behçet disease	heart failure). When polymyositis appears as a com-
	Other noninfectious	giant cell myositis	ponent of a collagenosis (Table 14.7) (“overlap syn-
	myositides	diffuse fasciitis with eosinophilia	drome”), other organs are affected as well. The only
		eosinophilic polymyositis	other disease affecting both the muscles and the skin is
		polymyalgia rheumatica	scleroderma.
		sarcoidosis
		myositis in Crohn disease	Diagnostic evaluation. Ancillary testing is usually nec-
		myositis ossificans
			essary. The serum CK concentration is elevated to 10
		myosclerosis
			times the normal value or more, at least initially. The
	Infectious myositides	viral (e. g., influenza virus)
			EMG reveals	markedly shortened, low, polyphasic
		bacterial	potentials, to a highly variable degree in different por-
		borrelial
			tions of the same muscle. Pathological spontaneous ac-
		fungal
			tivity and denervation potentials are also present.
		protozoal
		helminthic	Muscle biopsy typically reveals diffusely distributed
			muscle necrosis and inflammatory infiltrates.

Pathogenesis. Humoral factors play a role in dermatomyositis, while cellular immune mechanisms are involved in pure polymyositis.

Clinical manifestations. The illness often begins with constitutional symptoms such as fatigue, myalgias, joint

Treatment. Children tend to respond well to treatment with corticosteroids. Adults often require treatment with other immunosuppressive drugs, usually azathioprine. Immunoglobulins are beneficial in the initial stage of treatment but must always be supplemented with corticosteroids or immune suppressants over the course of time.

Other Diseases Affecting Muscle

Myopathies Due to Systemic Disease

A variety of general medical conditions cause muscle weakness, among them certain endocrinopathies (hypoand hyperthyroidism, hyperand hypoparathyroidism, Cushing disease, Addison disease). Paraneoplastic syndromes causing muscle weakness include paraneoplastic polyand dermatomyositis, as well as Lambert−Eaton syndrome, in which neuromuscular transmission is impaired (p. 277). Among the electrolyte disorders, hyperand hypokalemia (not of genetic origin) can cause muscle weakness, as can medications such as colchicine, chloroquine, fluorocortisone, and antilipemic agents. Toxic substances such as gasoline vapor and toluene can produce rhabdomyolysis (be aware of recreational sniffing as a possible cause!),

while alcohol can produce an acute alcoholic myopathy. Malnutrition, e. g., in prison camps, can lead to myastheniform disturbances, and vitamin E deficiency can lead to severe myopathy.

Congenital Myopathies

A number of types of congenital myopathy have been described and the genetic basis of some of them is now known. Their common features are:

markedly reduced muscle tone from infancy onward;

delayed motor development;

later, mainly proximal muscle weakness;

often, generally diminished muscle bulk;

Mumenthaler / Mattle, Fundamentals of Neurology © 2006 Thieme All rights reserved. Usage subject to terms and conditions of license.