Question: Can methylenetetrahydrofolate reductase (MTHFR) gene mutations cause homocystinuria?

Context:
Methylenetetrahydrofolate reductase (MTHFR) deficiency is a rare autosomal recessive disorder. 
Several mutations seen in methylenetetrahydrofolate reductase (MTHFR) give rise to the formation of hyperhomocysteinemia and homocystinuria, a considerable risk factor for cardiovascular and cerebrovascular disorders, by leading to enzymatic inactivation.
At admission, he had significantly elevated plasma and urine levels of total homocysteine, significantly decreased levels of folate in serum and cerebrospinal fluid, and a normal blood concentration of methionine.
Response to treatment demonstrated B(6)-non-responsive homocystinuria. Molecular study showed compound heterozygous T353 N and D444 N mutations of the cystathionine beta-synthase (CBS) gene, and also a C667T homozygous mutation of the methylenetetrahydrofolate-reductase (MTHFR) gene. 
Our case is atypical because of the absence of thromboembolism and the mild phenotype, in spite of being B(6)-non-responsive, and the association of a rare compound heterozygous mutation of the CBS gene and also an homozygous mutation of the MTHFR gene.
Molecular characterization of five patients with homocystinuria due to severe methylenetetrahydrofolate reductase deficiency.
Methylenetetrahydrofolate reductase (MTHFR) is a key regulatory enzyme in folate and homocysteine metabolism. Research performed during the past decade has clarified our understanding of MTHFR deficiencies that cause homocystinuria or mild hyperhomocysteinemia. Our cloning of the MTHFR coding sequence was initially followed by the identification of the first deleterious mutations in MTHFR, in patients with homocystinuria and marked hyperhomocysteinemia.
Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the regulation of plasma homocysteine levels. MTHFR deficiency, an autosomal recessive disorder, results in homocystinuria and hypomethioninaemia and presents with highly variable symptoms affecting many organs but predominantly the central nervous system. 
Some methylenetetrahydrofolate reductase (MTHFR) gene mutations cause hyperhomocysteinemia and homocystinuria.
Rare mutations in the MTHFR gene have been associated with autosomal recessive MTHFR deficiency leading to homocystinuria.
Characterization of six novel mutations in the methylenetetrahydrofolate reductase (MTHFR) gene in patients with homocystinuria.
Five patients suspected of having non-classical homocystinuria due to MTHFR deficiency were examined with respect to their symptoms, MTHFR enzyme activity and genotypes of the MTHFR gene.
The results of our study render the full-length characterisation of affected alleles in severe homocystinuria and moderate hyperhomocysteinaemia due to MTHFR deficiency and provide a basis for investigating the regulation of the human MTHFR gene.
Our cloning of the MTHFR coding sequence was initially followed by the identification of the first deleterious mutations in MTHFR, in patients with homocystinuria and marked hyperhomocysteinemia.
Different MTHFR mutations lead either to severe homocystinuria as a multisystem disorder or to moderate hyperhomocysteinaemia, which is a common risk factor for disorders ranging from cardiovasculopathy to spina bifida.
We studied 24 patients with homocystinuria caused by homozygous CBS deficiency from 18 unrelated kindreds for FVL and for the 677C-->T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene and investigated their possible interaction in the risk of venous thrombosis.
On the contrary, thermolabile MTHFR caused by the 677C-->T mutation, was frequently observed among homocystinuria patients, especially among those with thromboembolic complications: three of six homocystinuria patients who had suffered from a thromboembolic event had thermolabile MTHFR.
We studied 24 patients with homocystinuria caused by homozygous CBS deficiency from 18 unrelated kindreds for FVL and for the 677C-->T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene and investigated their possible interaction in the risk of venous thrombosis.
Some methylenetetrahydrofolate reductase (MTHFR) gene mutations cause hyperhomocysteinemia and homocystinuria
We studied 24 patients with homocystinuria caused by homozygous CBS deficiency from 18 unrelated kindreds for FVL and for the 677C-->T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene and investigated their possible interaction in the risk of venous thrombosis
Characterization of six novel mutations in the methylenetetrahydrofolate reductase (MTHFR) gene in patients with homocystinuria
The most common genetic cause of hyperhomocysteinemia is the 677C-->T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene
The 677C-->T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is an important cause of mild hyperhomocysteinemia, but this polymorphism does not seem to be a risk factor for venous thrombosis
Hyperhomocysteinemia and methylenetetrahydrofolate reductase (MTHFR) gene mutation have been postulated as a possible cause of recurrent miscarriage (RM)
The 677C>T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is an important cause of mild hyperhomocysteinaemia
We studied 24 patients with homocystinuria caused by homozygous CBS deficiency from 18 unrelated kindreds for FVL and for the 677C-->T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene and investigated their possible interaction in the risk of venous thrombosis. 
AIM: Some methylenetetrahydrofolate reductase (MTHFR) gene mutations cause hyperhomocysteinemia and homocystinuria. 
Betaine for treatment of homocystinuria caused by methylenetetrahydrofolate reductase deficiency.
Severe deficiency of methylenetetrahydrofolate reductase (MTHFR) with homocystinuria can result in early demise or later-onset neurological impairment, including developmental delay, motor dysfunction, and seizures. 
Deficiency of 5,10-methylenetetrahydrofolate reductase (MTHFR) leads to deficient remethylation of homocysteine and is one of the causes of homocystinuria. 
Neurological disturbances have been described in homocystinuria caused by severe MTHFR deficiency. 
The 677C-->T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is an important cause of mild hyperhomocysteinemia, but this polymorphism does not seem to be a risk factor for venous thrombosis.
Research performed during the past decade has clarified our understanding of MTHFR deficiencies that cause homocystinuria or mild hyperhomocysteinemia.
The 677C>T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is an important cause of mild hyperhomocysteinaemia.
The most common genetic cause of hyperhomocysteinemia is the 677C-->T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene.
Our cloning of the MTHFR coding sequence was initially followed by the identification of the first deleterious mutations in MTHFR, in patients with homocystinuria and marked hyperhomocysteinemia.
Characterization of six novel mutations in the methylenetetrahydrofolate reductase (MTHFR) gene in patients with homocystinuria.
Molecular characterization of five patients with homocystinuria due to severe methylenetetrahydrofolate reductase deficiency.
On the contrary, thermolabile MTHFR caused by the 677C-->T mutation, was frequently observed among homocystinuria patients, especially among those with thromboembolic complications: three of six homocystinuria patients who had suffered from a thromboembolic event had thermolabile MTHFR.

Answer: Yes, several methylenetetrahydrofolate reductase (MTHFR) gene mutations can cause homocystinuria and hyperhomocysteinemia.
Exact answer: yes