Carnitine Uptake Deficiency vs LCAD deficiency

SDN Members don't see this ad. (About Ads)

How do you distinguish between these two? The question I got stuck was...

Two 4mo old baby has progressive weakness, diminished deep tendon reflex, and a frog-leg position since infancy. The parents say that both boys experienced seizure accompanied by hypoketotic hypoglycemia. One twin dies at 5 months of age. At 3 years of age, the surviving twin is diagnosed with cardiomegaly and lab tests show elevated carnitine esters in both muscle tissue and serum. What is the diagnosis?

ans: Carnitine "uptake" deficiency vs LCAD deficiency

The answer says I can rule out carnitine "uptake" deficiency because of carnitine esters (long chain acyl carnitines) are accumulating in serum and in muscle tissue but I was having trouble understanding how this rules out carnitine "uptake" deficiency. Would someone explain this pleaes?

Thanks.

Edit: I'm sorry, I actually forgot the key word "uptake" in carnitine deficiency.

Originally Posted by hantah

How do you distinguish between these two? The question I got stuck was...

Two 4mo old baby has progressive weakness, diminished deep tendon reflex, and a frog-leg position since infancy. The parents say that both boys experienced seizure accompanied by hypoketotic hypoglycemia. One twin dies at 5 months of age. At 3 years of age, the surviving twin is diagnosed with cardiomegaly and lab tests show elevated carnitine esters in both muscle tissue and serum. What is the diagnosis?

ans: Carnitine deficiency vs LCAD deficiency

The answer says I can rule out carnitine deficiency because of carnitine esters (long chain acyl carnitines) are accumulating in serum and in muscle tissue but I was having trouble understanding how this rules out carnitine deficiency. Would someone explain this pleaes?

Thanks.

A deficiency means you don't have something. If they have carnitine, they can't be deficient in it.

I see what you're getting at.

The carnitine shuttle is used to bring long-chain fatty-acyl-CoAs into the mitochondria. In acyl-CoA dehydrogenase deficiency, there will be a buildup of both long-chain fatty-acyl CoAs in addition to saturation of the carnitine transporter (I'm assuming this refers to "long-chain acyl carnitine"). We can only get the latter because the deficient enzyme is downstream to the carnitine transporter, which means that the carnitine transporter itself cannot be deficient. If long-chain acyl-carnitines were absent, that would imply that carnitine is not available or able to bond with the long-chain fatty-acyl-CoAs, so only if that were the case would carnitine deficiency be appropriate as a diagnosis.