lipid storage disease

Any of a group of relatively rare hereditary disorders of fat metabolism in which enzyme defects cause distinctive types of lipids to accumulate.

They include Tay-Sachs disease, Gaucher disease, Niemann-Pick disease, and Fabry disease. Several are untreatable and cause death before age five; others occur in adulthood.

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▪ medical disorder

      any of a group of relatively rare hereditary disorders of fat metabolism, characterized by the accumulation of distinctive types of lipids, notably cerebrosides, gangliosides, or sphingomyelins, in various body structures. Each type of lipid accumulates as a result of a defect in one of the several organic catalysts or enzymes that normally metabolize it inside the cell.

      In Gaucher's disease (Gaucher disease), abnormal amounts of cerebrosides accumulate in the liver, spleen, bone marrow, and lymph nodes. The defective enzyme is glucocerebrosidase. The excess lipids, stored in the large distended Gaucher cells that are typical of the disease, interfere with cell function and produce two distinctive syndromes: (1) An acute cerebral form chiefly affects infants, who appear normal at birth but soon become apathetic and retarded in their development; enlargement of their abdomen is followed by severe nervous system symptoms, and death usually occurs during the first year of life. (2) A more chronic form that may become evident at any age is characterized by an enlargement of the spleen, by anemia, and by a patchy brown pigmentation of the skin; the bones show characteristic changes in shape, and interference with calcification may result in fractures and deformities.

       Niemann-Pick disease has many clinical features in common with Gaucher's disease, but in this case the deposition of lipids in the body is more widespread and the lipids involved are sphingomyelins. The defective enzyme is sphingomyelinase. The disease is usually apparent during the first year of life, and affected children seldom live beyond their fourth year.

      In Tay-Sachs disease, or amaurotic (blind) idiocy, gangliosides are deposited in body tissues, chiefly those of the central nervous system, which deteriorates, resulting in severe mental deficiency. Characteristic early symptoms of Tay-Sachs disease include extreme sensitivity to noise, muscle weakness, and the appearance of a cherry-red spot on the small, highly sensitive area near the centre of the retina, this red spot being sometimes also seen in Niemann-Pick disease. Progressive loss of vision eventually results in blindness. Affected children generally die at about three years of age. Niemann-Pick disease and Tay-Sachs disease are both seen more frequently among individuals of Jewish ancestry than among others.

      In Fabry's disease, characteristic symptoms include the appearance of many purplish papules (small, solid elevations) on the skin, enlargement of the heart, poor kidney function, opacity of the cornea, and dilated blood vessels. These symptoms result from the deposition of the lipid ceramide trihexoside, closely related to the sphingomyelins, in the affected body structures. The defective enzyme is ceramide trihexosidase. Fabry's disease is sex-linked, affecting chiefly males, who generally die of kidney failure complicated by cardiovascular disease. Except for alleviating the symptoms, there is no specific treatment for any of the lipid storage diseases.

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