Why would someone have normal levels of homocysteine in their blood, but high levels of homocysteine in their urine?

Homocystinuria is a: Disorder with autosomal recessive inheritance. Both parents pass on a mutation of either the mthfr gene on the short arm of chromosome (chr.) 1 or the cbs gene on the long arm of chr. 21, causing deficiency in the respective enzymes for which they code. A metabolic geneticist, hematologist or cardiologist can help your doctor with diagnosis.Some specific forms of hcu respond to specific treatment.