Myositis 273
	The mitochondrial genome. Mitochondria have two	Table 14.6 Clinical manifestations of mitochondrial diseases
	copies of the nuclear DNA (nDNA) at their disposal, but
		Organ	Manifestation
	also multiple copies of their own mitochondrial DNA
		Muscle	myopathy with ragged red fibers
	(mtDNA). Mitochondrial DNA is transmitted from
	generation to generation through the oocyte, independ-		progressive external ophthalmoplegia
	ently of the nuclear genome. Thus, mitochondrial dis-		exercise intolerance
	eases caused by mtDNA defects are inherited in a mater-	Nervous system	myoclonus and generalized seizures
	nal pattern.		stroke in younger individuals
			ataxia
	General clinical manifestations of mitochondrial dis-		dementia
			polyneuropathy
	ease. Disturbances of mitochondrial metabolism impair
			deafness
	the function of nearly all cells in the body. Muscle and
			optic neuropathy
	brain cells are particularly strongly affected because of		migraine
	their high-energy requirements. Thus, mitochondrial		basal ganglionic calcification
	diseases often express themselves clinically as an en-		(Fahr syndrome)
	cephalomyopathy. The typical clinical features are sum-		dystonia
	marized in Table 14.6.		elevated CSF protein concentration

Examples of Mitochondrial Myopathies

Progressive external ophthalmoplegia usually has its onset in adulthood and progresses very slowly. Its typical features are progressive ptosis and restriction of ocular motility, so that, in the end, all movements of the eyes are impossible. Skeletal muscle biopsy with Gomori trichrome staining reveals accumulations of mitochondria in so-called “ragged red fibers.” The condition can appear as a familial disease of maternal inheritance or as a component of Kearns−Sayre syndrome (see below).

Kearns−Sayre syndrome (KSS) is characterized by progressive external ophthalmoplegia combined with retinal pigment degeneration and an intracardiac conduction defect. There may be further clinical manifestations as well (cf. Table 14.6). KSS is usually familial and is due to a point mutation in the mitochondrial DNA.

MELAS syndrome consists of mitochondrial myopathy, encephalopathy, lactic acidosis, and “strokelike epi-

Eye	retinitis pigmentosa
	cataract
Heart	cardiomyopathy
	conduction abnormalities
Gastrointestinal	intestinal pseudoobstruction
system	diarrhea
Endocrine system	short stature
	diabetes
	goiter
	hypogonadism
Skin	multiple lipomas
	ichthyosis

sodes.” It presents in childhood with transient cerebral ischemia, episodic vomiting, and often, later, dementia. The serum lactic acid concentration is elevated.

MERRF syndrome (myoclonus epilepsy with ragged red fibers) is a rare syndrome characterized by myoclonus, generalized epileptic seizures, myopathy, and dementia.

Myositis

Myositis is an infectious or inflammatory disease of muscle. The various types of myositis include:

autoimmune diseases affecting muscle, either as the major disease manifestation (as in polymyositis, which sometimes affects the skin as well = dermatomyositis) or as an accompanying manifestation in a larger syndrome;

muscle involvement by a primary, systemic, noninfectious, chronic inflammatory disease;

direct infection of muscle (infectious myositis).

The most important types of myositis are listed in Table 14.7.

ArgoOneBold

ThiemeArgoOne

General clinical manifestations. The common features of infectious and inflammatory myopathies are:

usually symmetrical muscle involvement;

usually very rapid progression, within a few months;

sometimes, local pain;

lack of a sensory deficit;

sometimes, very high serum CK concentration;

lack of a family history.

In this chapter, we will restrict ourselves to a description of polymyositis and dermatomyositis.

Polymyositis and Dermatomyositis

Epidemiology. The incidence of these conditions is low: they strike only five to 10 per 100 000 individuals per year. Women are more commonly affected. The disease usually appears either before puberty or around age 40.

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

Diseases of Muscle

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