biochem: Sphingolipidoses (Lysosomal Storage Diseases)

Gaucher disease: deficient enzyme, accumulated substrate

Deficient Enzyme: B-glucosidase (glucocerebrosidase)

Accumulated Substrate: Glucocerebroside

Niemann-Pick Disease: deficient enzyme, accumulated substrate

Deficient Enzyme: Sphingomyelinase

Accumulated Substrate: Sphingomyelin

Tay-sachs disease: deficient enzyme, accumulated substrate

Deficient Enzyme: Hexosaminidase A

Accumulated Substrate: GM2 ganglioside

Fabry disease: deficient enzyme, accumulated substrate

Deficient Enzyme: a-galactosidase A

Accumulated Substrate: Globotriaosylceramide(Gb3)

Krabbe disease: deficient enzyme, accumulated substrate

Deficient Enzyme: Galactocerebrosidase

Accumulated Substrate: Globotriaosylceramide(Gb3)

Gaucher disease

Hepatosplenomegaly, osteoporosis, "wrinkled tissue paper" Gaucher cells. (Most common).

Niemann-Pick Disease

Hepatosplenomegaly, neurodegeneration, cherry-red spot on macula, foam cells

Tay-Sachs Disease

Progressive neurodegeneration, cherry-red spot on macula, NO hepatosplenomegaly, onion-skin lysosomes.

Fabry Disease

Angiokeratomas, burning peripheral neuropathies, renal/cardiac failure. (X-linked Recessive)

Krabbe Disease

Globoid cells, optic atrophy, demyelination, severe mental impairment.

Tay-Sachs vs. Niemann-Pick (The "Cherry-Red Spot" Battle)

^{Both diseases present in infancy with neurodegeneration, developmental regression, and a cherry-red spot on the macula.}

Tay-SaX lacks Hexosaminidase A and lacks hepatosplenomegaly.

No man Picks his nose with his HepatoSpleen (Niemann-Pick has organ enlargement)

Gaucher vs. Niemann-Pick (Histology Battle)

^{Both feature hepatosplenomegaly and lipid-laden macrophages, but the microscopic appearance differs:}

Gaucher Disease: Macrophages have cytoplasm resembling "crumpled tissue paper" or "wrinkled tissue" due to glucocerebroside accumulation.

Niemann-Pick Disease: Macrophages appear foamy ("foam cells" or "sea-blue histiocytes") filled with sphingomyelin.

Fabry Disease (The Standout)

^{Fabry is the only X-linked recessive sphingolipidosis. Look for the triad in a male patient:}

Angiokeratomas (dark red skin lesions in bathing-suit distribution)

Peripheral neuropathy (burning pain in fingers and toes)

Decreased sweating (anhidrosis) progressing to early kidney failure

Tay-Sachs = TAX = Hexosaminidase A (GM2)

Tay-Sachs

a-Galactosidase A (accumulates Ceramide trihexoside)

Fabry: Fabry's galaxative

Gaucher = Glucocherebrosidase = Gaucher cells (Crumpled tissue)

Gaucher

Niemann-Pick = No Pick = Sphingomyelinase (Sphingomyelin)

Niemann-Pick

Galactocerebrosidase = Globoid cells

Krabbe

Arylsulfatase A = Sulfatides (Myelin loss)

Metachromatic

Only X-Linked Sphingolipidosis

Fabry disease (a-Galactosidase A deficiency)

Most Common Sphingolipidosis

Gaucher disease (Glucocerebrosidase deficiency; Gaucher cells)

Cherry-Red Spot + NO Organomegaly

Tay-Sachs (Hexosaminidase A deficiency)

Cherry-Red Spot + WITH Organomegaly

Niemann-Pick (Sphingomyelinase deficiency)

Demyelination with Sulfatides

Metachromatic Leukodystrophy (Arylsulfatase A deficiency)

Globoid Cells

Krabbe disease (Galactocerebrosidase deficiency)