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sphingolipidoses for under graduate medical students

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  1. 1. Sphingolipidoses Dr.S.Sethupathy, M.D.,Ph.D., Department of Biochemistry, Rajah Muthiah Medical College, Annamalai University
  2. 2. Sphingolipids The sphingolipids a complex range of lipids in which fatty acids are linked via amide bonds to a long-chain base or sphingoid. They are also found in a few bacterial genera - Sphingomonas and Sphingobacterium.
  3. 3. Globoside
  4. 4. PAPS synthase
  5. 5. Lysosomal storage diseases The lysosomal storage diseases are a rare class of neurometabolic disorders. Metabolites of complex lipids accumulate within neurons. Mostly autosomal recessive fashion For genetic counseling and for monitoring future pregnancies.
  6. 6. Sphingolipidoses They are characterized by a progressive degenerative disease of the nervous system, with blindness, dementia, epilepsy, ataxia, paralysis, and hyperreflexia. A cherry-red spot at the macula and optic atrophy are the most common signs Ophthalmologic examination - an important clue to the diagnosis.
  7. 7. Cherry red spot
  8. 8. Gangliosides  Gangliosides are important constituents of gray matter.  They are glycosphingolipids that contain sialic acid in the oligosaccharide chain.  The metabolism of ganglioside involves the removal of the terminal galactose to convert GM1-ganglioside to GM2-ganglioside.  GM2-ganglioside is then hydrolyzed to GM3- ganglioside by the removal of N- acetylgalactosamine.
  9. 9. D.Blue –GLU, L.Blue- sialic acid, W-NAcGal, Y- Gal
  10. 10. Gangliosidoses They are neuronal lipid storage disorders due to deficiencies of certain lysosomal hydrolases. Autosomal recessive inheritance Progressive mental and motor deterioration Due to the storage of GM1- or GM2- ganglioside in neurons.
  11. 11. Prognosis  Lysosomal storage diseases are ultimately fatal  There is no effective treatment.  Almost all the disorders diagnosed by enzyme analysis.  Leukocytes and cultured skin fibroblasts or serum can be assayed for enzyme activity  Prenatal diagnosis is also possible.
  12. 12. Disease Enzyme Diagnostic Sample(s) GM2-gangliosidosis Tay-Sachs disease Hex A deficient Leukocyte serum Sandhoff's disease Hex A and B deficient Leukocyte serum AB variant Hex A, B normal GM2loading studies in fibroblasts B1variant Hex A deficient with sulfated substrate Leukocyte fibroblasts Juvenile GM2- gangliosidosis Partial Hex A deficiency Leukocyte serum Infantile GM1- gangliosidosis ß-Galactosidase deficient Leukocyte fibroblasts Niemann-Pick disease Type A, infantile Sphingomyelinase deficient Leukocyte fibroblasts Type B Sphingomyelinase deficient Leukocyte fibroblasts Farber's lipogranulomatosis Ceramidase Leukocyte fibroblasts Sialidoses Type 1 Sialidase deficient Fresh fibroblasts Type 2 Sialidase and ß-galactosidase deficient Fresh fibroblasts