Errors of Inborn Metabolism (Homocysteineuria)

Question 1

What are the clinical findings associated with homocysteineuria?

Answer 1

Increased homocysteine in urine, mental retardation, osteoperosis, tall structure, lens subluxation (both downward and inward) and atherosclerosis (resulting in increased chances of strokes and MI).

Question 2

What two amino acids can homocysteine turn into and how?

Answer 2

Homocystiene + B12 turns it into methionine. Whereas homocysteine turns into cystathionine with the enzyme cystathionine synthase (and serine and B6 as a cofactor). Cystathionine then is converted into cysteine.

Question 3

What are the 3 things that can cause homocysteinuria? How to tx each of these case?

Answer 3

1. Cystathionine synthase deficiency, and tx this wil decreased methionine, increased cysteine, folate and B12 in diet.
2. Decreased affinity of the Cystathionine synthase for pyridoxal phosphate (treat with increased B6 in diet).
3. Homocysteine methyltransferase deficiency, this requires B12.

Question 4

What is the problem basically with homocysteinuria?

Answer 4

Homocysteine is not being converted into cysteine because of cystathionine synthase dysfunction, homocysteine accumulates and causes mental retardation, atherosclerosis, etc etc.