1. Deterioration; passing from a higher to a lower level or type. 2. A worsening of mental, physical, or moral qualities. 3. A retrogressive pathologic change in cells or tissues, in consequence of which their functions are often impaired or destroyed; sometimes reversible; in the early stages, necrosis results. SYN: retrograde metamorphosis. SYN: degeneratio. [L. degeneratio]
- adipose d. SYN: fatty d..
- adiposogenital d. SYN: adiposogenital dystrophy.
- age-related macular d. a common macular d. beginning with drusen of the macula and pigment disruption and sometimes leading to severe loss of central vision.
- amyloid d. infiltration of amyloid between cells and fibers of tissues and organs. SYN: waxy d. (1).
- angiolithic d. calcareous d. of the walls of the blood vessel s.
- ascending d. 1. retrograde d. of an injured nerve fiber; i.e., toward the nerve cell of the fiber; 2. spinal cord d. that begins in one region and then progresses cephalad.
- atheromatous d. focal accumulation of lipid material (atheroma) in the intima and subintimal portion of arteries, eventually resulting in fibrous thickening or calcification.
- axon d. SYN: axonal d..
- axonal d. a type of peripheral nerve fiber response to insult, wherein axon death and subsequent breakdown occurs, with secondary breakdown of the myelin sheath associated; caused by focal injury to peripheral nerve fibers; often referred to as wallerian d.. SYN: axon d..
- ballooning d. an obsolete term for cells that are infected with certain viruses, resulting in conspicuous swelling of the cell and cytoplasmic vacuolation.
- basophilic d. blue staining of connective tissues when hematoxylin-eosin stain is used; found in such conditions as solar elastosis.
- calcareous d. in a precise sense, not a degenerative process per se, but the deposition of insoluble calcium salts in tissue that has degenerated and become necrotic, as in dystrophic calcification.
- carneous d. SYN: red d..
- caseous d. SYN: caseous necrosis.
- colloid d. a d. similar to mucoid d., in which the material is inspissated.
- cone d. SYN: cone dystrophy.
- corticobasal d. a rare, progressive disease involving both cerebral cortex and extrapyramidal structures; clinically manifest as disturbances of voluntary movements and rigidity; pathologic characteristics include d. of the cerebral cortex with balloon neurons and d. of the substantia nigra.
- Crooke hyaline d. SYN: Crooke hyaline change.
- descending d. 1. wallerian d. of an injured nerve fiber; i.e., d. distal to the lesion; 2. d. caudal to the level of a spinal cord lesion.
- disciform d. foveal or parafoveal subretinal neovascularization with retinal separation and hemorrhage leading finally to a circular mass of fibrous tissue with marked loss of visual acuity. SYN: disciform macular d..
- elastoid d. 1. SYN: elastosis (2). 2. hyaline d. of the elastic tissue of the arterial wall, seen during involution of the uterus.
- elastotic d. SYN: elastosis (2).
- familial pseudoinflammatory macular d. [MIM*136900] macular d. that occurs during the fifth decade of life, with sudden development of a central scotoma in one eye followed rapidly by a similar lesion in the opposite eye; autosomal dominant inheritance. SYN: Sorsby macular d..
- fascicular d. d. restricted to certain fascicles of nerves or muscles.
- fatty d. abnormal formation of microscopically visible droplets of fat in the cytoplasm of cells, as a result of injury. SYN: adipose d., steatosis (2).
- fibrinoid d., fibrinous d. a process resulting in poorly defined, deeply acidophilic, homogeneous refractile deposits with some staining reactions that resemble fibrin, occurring in connective tissue, blood vessel walls, and other sites.
- fibrous d. not a d. per se, but rather a reparative process; cells and foci of tissue previously affected with degenerative processes, and necrosis, are replaced by cellular fibrous tissue.
- granular d. SYN: cloudy swelling.
- granulovacuolar d. d. of hippocampal brain cells in elderly persons, characterized by basophilic granules surrounded by a clear zone in hippocampal neurons; occurs more frequently in Alzheimer disease.
- gray d. d. of the white substance of the spinal cord, the fibers of which lose their myelin sheaths and become darker in color.
- hepatolenticular d. SYN: Wilson disease (1).
- hyaline d. a group of several degenerative processes that affect various cells and tissues, resulting in the formation of rounded masses (“droplets”) or relatively broad bands of substances that are homogeneous, translucent, refractile, and moderately to deeply acidophilic; may occur in the collagen of old fibrous tissue, smooth muscle of arterioles or the uterus, and as droplets in parenchymal cells.
- hyaloideoretinal d. [MIM*143200] progressive liquefaction and destruction of the vitreous humor with grayish-white preretinal membranes, myopia, cataract, retinal detachment, and hyper- and hypopigmentation; autosomal dominant inheritance. SYN: Wagner disease, Wagner syndrome.
- hydropic d. SYN: cloudy swelling.
- infantile neuronal d. degenerative disorder of infants with widespread neuronal loss in thalamus, cerebellum, pons, and spinal cord, resembling infantile muscular atrophy.
- liquefaction d. 1. necrosis with softening, as in ischemic brain tissue; 2. dissolution of the basal epidermal layer by necrosis of scattered cells with vacuolization, observed in lichen planus, lupus erythematosus, and other dermatologic conditions.
- macular d. any ocular d. affecting predominately the posterior fundus, but most commonly age-related macular d..
- Mönckeberg d. SYN: Mönckeberg arteriosclerosis.
- mucinoid d. a term including both mucoid and colloid d., the essential cellular changes in both being similar, the only difference being that, in colloid d., the substance is firmer and more inspissated than in mucoid d., in which it is thin and jellylike.
- mucoid d. a conversion of any of the connective tissues into a gelatinous or mucoid substance. SYN: myxoid d., myxomatous d., myxomatosis (1).
- mucoid medial d. SYN: cystic medial necrosis.
- myelinic d. formation of myelin figures in the cytoplasm of cells, possibly by degradation or hydration of lipoprotein of self-digested organelles.
- myxoid d., myxomatous d. SYN: mucoid d..
- neurofibrillary d. formation of coarse, argentophilic, intracytoplasmic fibers, often in complex tangles within intracranial nerve cells. SEE ALSO: Alzheimer disease.
- Nissl d. d. of the cell body occurring after transection of the axon; characterized by dispersion of the granular endoplasmic reticulum, swelling of the soma, and an eccentric position of the nucleus of the cell.
- parenchymatous d. SYN: cloudy swelling.
- pellucid marginal corneal d. bilateral opacification and vascularization of the periphery of the cornea, progressing to formation of a gutter and ectasia. SYN: ectatic marginal d. of cornea.
- primary neuronal d. SYN: Alzheimer disease.
- pseudotubular d. obsolete term for a form of d. observed in adrenal glands, especially those of patients with febrile infectious disease; the shrunken, lipid-depleted cells of the zona fasciculata (and sometimes the zona glomerulosa) are arranged in a circular pattern about spaces that may be empty or partly filled with fibrin, necrotic cells, or amorphous material.
- red d. obsolete term for necrosis, with staining by hemoglobin, which may occur in uterine myomas, especially during pregnancy; marked by softening and a red color resembling partly cooked meat. SYN: carneous d..
- reticular d. severe epidermal edema resulting in multilocular bullae.
- retrograde d. retrograde cell d. with chromatolysis of Nissl bodies and peripheral displacement of the nucleus of the cell of origin of a nerve fiber injured or sectioned.
- Salzmann nodular corneal d. large and prominent nodules of a solid, opaque material that stands out from the surface of the cornea; occurs occasionally in persons previously affected by phlyctenular keratitis.
- senile d. the process of involution occurring in old age.
- snail track d. circumferential line of fine white dots in the peripheral retina associated with atrophic retinal holes.
- Sorsby macular d. SYN: familial pseudoinflammatory macular d..
- spheroidal d. SYN: climatic keratopathy.
- spongy d. of infancy SYN: Canavan disease.
- subacute combined d. of the spinal cord a subacute or chronic disorder of the spinal cord, such as that occurring in certain patients with vitamin B12 deficiency, characterized by a slight to moderate degree of gliosis in association with spongiform d. of the posterior and lateral columns. SYN: combined sclerosis, combined system disease, funicular myelitis (2), Putnam-Dana syndrome, vitamin B12 neuropathy.
- tapetoretinal d. [MIM*272600] a hereditary disorder of the retina mainly affecting photoreceptors and retinal pigment epithelium; this may be a manifestation of Friedreich ataxia, Refsum disease, and abetalipoproteinemia. SYN: primary pigmentary d. of retina.
- transsynaptic d. an atrophy of nerve cells following damage to the axons that make synaptic connection with them; noted especially in the lateral geniculate body. SYN: transneuronal atrophy, transsynaptic chromatolysis.
- Türck d. d. of a nerve fiber and its sheath distal to the point of injury or section of the axon; usually applied to d. within the central nervous system.
- vacuolar d. formation of nonlipid vacuoles in cytoplasm, most frequently due to accumulation of water by cloudy swelling.
- vitelliform d. [MIM*153700] SYN: Best disease. SYN: vitelliruptive d..
- vitelliruptive d. SYN: vitelliform d..
- wallerian d. the degenerative changes the distal segment of a peripheral nerve fiber (axon and myelin) undergoes when its continuity with its cell body is interrupted by a focal lesion.
- waxy d. 1. SYN: amyloid d.. 2. SYN: Zenker d..
- xerotic d. scarring of the conjunctiva associated with keratinized epithelium.
- Zenker d. obsolete term for a form of severe hyaline d. or necrosis in skeletal muscle, occurring in severe infections. SYN: waxy d. (2).

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de·gen·er·a·tion di-.jen-ə-'rā-shən, .dē- n
1) intellectual or moral decline tending toward dissolution of character or integrity: a progressive worsening of personal adjustment
2 a) progressive deterioration of physical characters from a level representing the norm of earlier generations or forms: regression of the morphology of a group or kind of organism toward a simpler less highly organized state <parasitism leads to \degeneration>
b) deterioration of a tissue or an organ in which its vitality is diminished or its structure impaired esp deterioration in which specialized cells are replaced by less specialized cells (as in fibrosis or in malignancies) or in which cells are functionally impaired (as by deposition of abnormal matter in the tissue)

* * *

the deterioration and loss of specialized function of the cells of a tissue or organ. The changes may be caused by a defective blood supply or by disease. Degeneration may involve the deposition of calcium salts, fat (see fatty degeneration), or fibrous tissue in the affected organ or tissue. See also infiltration.

* * *

de·gen·er·a·tion (de-jen″ər-aґshən) [L. degeneratio] deterioration; change from a higher to a lower form; especially change of tissue to a less functionally active form. degenerative adj

Medical dictionary. 2011.

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