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Nutritional and Metabolic Disorders

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In Tay-Sachs disease, the enzymatic abnormality responsible for the neurological deficits is deficiency of which of the following?

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a. Hexosaminidase A

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b. Glucocerebrosidase

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c. Phosphofructokinase

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d. Glucose phosphorylase

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e. Sphingomyelinase

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The answer is a. Children with Tay-Sachs disease die prematurely and exhibit mental retardation, seizures, and blindness. This is a ganglioside storage disease that occurs more commonly in Ashkenazi Jews than in the general population. The early-onset form will produce macrocephaly and a cherry red spot in the fundus.

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An 8-month-old boy develops spasticity, head retraction, and difficulty swallowing. His physician discovers an abnormal accumulation of glucosylceramide and tells the parents their child will continue to deteriorate and likely die within 3 years. This child has which of the following?

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a. β-glucosidase deficiency

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b. Niemann-Pick disease

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c. Krabbe disease

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d. Fabry disease

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e. Tay-Sachs disease

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The answer is a. The disease responsible for the accumulation of glucosylceramide is Gaucher disease. Gaucher disease is inherited as an autosomal recessive trait and may be diagnosed by demonstrating deficient glucocerebrosidase in fibroblasts or leukocytes. The severity of disease varies from nonneuronopathic types to acute infantile neuronopathic disease. Gaucher disease produces hepatosplenomegaly and may cause lethal CNS disease. It is one of a collection of storage diseases called sphingolipidoses, which include Niemann-Pick disease, Krabbe disease, and Fabry disease. Fabry disease involves the accumulation of another ceramide, trihexosylceramide. All the sphingolipids are nothing more than lipids that contain a sphingosine moiety. Sphingosine is a class of long-chain compounds with hydroxyl groups on carbons 1 and 3 and an amino group on carbon 2. They form ceramides by joining with fatty acids across the subterminal amino group. GM2 ganglioside accumulates in Tay-Sachs disease, and galactosyl sulfatides accumulate in metachromatic leukodystrophy.

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A 53-year-old left-handed man presents with asterixis, esophageal varices, splenomegaly, and abdominal ascites. He is likely to exhibit altered consciousness on the basis of which of the following?

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a. Renal tubular acidosis

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b. Impaired hepatic detoxification of portal blood

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c. Splenomegaly-induced anemia

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d. Copper intoxication

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e. Vitamin B12 deficiency

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The answer is b. The clinical picture presented suggests hepatic failure. Copper poisoning may lead to ...

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