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What is the most common monogenic disorder of carbohydrate metabolism?

classical galactosemia


What enzyme is defective in classical galactosemia?

galactose-1-phosphate uridyl transferase


What are some clinical manifestations of classical galactosemia?

failure to thrive, hepatic insufficiency cataracts and developmental delay.


Scenario: patient presents with accumulations of urea precursors such as ammonium and glutamine. It's also noted that this is an X-linked disorder. What enzyme is defective?

ornithine transcarbamylase (OTC deficiency)


Van Gierke’s disease is a defective storage disorder of what substance?



What enzyme is defective in Van Gierke’s disease?

G6 phosphatase


Case scenario: baby presents with poor feeding, failure to thrive, hepatic and renal insufficiency and death. It is noted that the baby cannot metabolize fructose properly. What enzyme is defective?

fructose 1,6-bisphophate aldolase


What is characteristics about Mucopolysaccharidoses (MPS disorders)?

Caused by a reduced ability to degrade one or more glycosaminoglycans (GAGs)


What are some clinical features of Mucopolysaccharidoses (MPS disorders)?

chronic and progressive multisystem deterioration, which causes hearing, vision, joint and cardiovascular dysfunction


What enzyme is defective in Phenylketonuria (PKU)

Mutation of phenylalanine hydroxylase (PAH)


What is defective to cause Gaucher disease?

acid β-glucosidase


What are the clinical characteristics of Gaucher disease?

visceromegaly, multiorgan failure, and debilitating skeletal disease.


What is defective in I-cell disease?

recognition marker of mannose-6-phoshate causing partially degraded oligosaccharides, lipids and glycosaminoglycans


What are the clinical manifestations in I-cell diesase?

coarse facial features, skeletal abnormities, corneal opacities, mental retardation and early death


What is defective in cystinuria disease?

Caused by abnormal cystine transport between cells and the extracellular environment cause cystinuria


Which AA's are secreted in high amounts in the urine in cystinuria?

cystine, lysine, arginine and ornithine


What are the clinical manifestations in cystinuria disease?

kidney stones


What is defective in Wilson's disease?

excess of copper caused by defective excretion of copper into the biliary tract


What are the clinical manifestations in Wilson's diesase?

causes progressive liver disease and neurological abnormalities. It is an autosomal recessive disorder. Patients with Wilson’s usually present with acute or chronic liver disease in childhood. Adults develop neurological symptoms such as dysarthria (inability to correctly articular words) and diminished coordination. One of the characteristic is the finding in the eye- Kayser-Fleischer ring


What is defective in MCAD disease?

deficiency of medium-chain acyl-coenzyme dehydrogenase (MCAD)


What are the clinical manifestations in MCAD disease?

episodic hypoglycemia, which is often provoked by fasting


What is defective in hemochromatosis?

disorder of iron metabolism in which excessive iron is absorbed in the small intestine and then accumulates in a variety of organs such as the liver, kidney, heart, joints and pancreas. It's a defect in the regulation of transport


What type of genetic disorder is hemochromatosis?

Autosomal recessive


What are the clinical manifestations in hemochromatosis?

delayed age on onset of fatigue, joint pain, diminished libido, diabetes, increased skin pigmentation, cardiomyopathy, liver enlargement and cirrhosis.


What is defective in Congenital adrenal hyperplasia (CAH)?

95% of CAH is caused by mutation in CYP21A2, the gene that encodes 21-hydroxylase


What are the clinical manifestations in CAH?

cortisol deficiency, variable deficiency of aldosterone and an excess of androgen


What is defective in Maple syrup urine disease?

Defect in branched-chained α-ketoacid dehydrogenase(BCKAD)


Which AA's are branched chain?

Valine, Leucine and isoleucine


What are the clinical manifestations in Maple syrup urine disease?

Without treatment, accumulation of BCAAs and their associated ketoacids leading to progressive neurodegeneration and death


What is defective in Zellwegger syndrome?

It is caused by mutations in genes that encode peroxins. These proteins are necessary both for peroxisome biogenesis and for importing proteins of the peroxisomal matrix and membrane