The aim is to reduce homocysteine by remethylating it

Treatment of homocystinuria

  1. RESTRICTION of methionine

  2. Betaine SUPPLEMENTION which increases Methionine

Mam, Please explain this contradiction !

The aim is to reduce homocysteine by remethylating it

It will form methionine

As we already have enough methionine awe restrict it otherwise more homocysteine will be produced from it

We are giving vitamin b6 and betaine so that all the accumulated homocystine can convert to methionine… On top of that, why you have to supplement extra methionine which causes overload…!

methionine level is “already” normal in classic homocystinuria

Because the defect is in beta cystathionine synthase

We have to reduce excess homocystine in some way, right? We are giving b6 to convert homocystine to cysteine. Betaine to convert homocystine to methionine…

Thus reducing homocystine levels…

so what about methionine overload as you said before? Methionine has only one fate- get converted to homocysteine later

No… Methionine is converted to S adenosyl methionine which is used for myelination .

With help of vitamin b12.

in classical homocystinuria, methionine levels are more than normal…

We have to restrict dietary methionine… At the same time, we have to reduce excess homocysteine by converting it to methionine and cysteine. But whatever B6 given, cysteine production will be less than normal, so cysteine should be added in diet. Methionine is more than normal, so dietary restriction.

yes I just checked Harrison’s. It is given that plasma methionine is increased

But mam said it is normal (which is wrong as per Harrison)

According to Harrison, the treatment is justified