Estimated prevalence of moderate to severely elevated total homocysteine levels in the United States: A missed opportunity for diagnosis of homocystinuria?

Classical homocystinuria (HCU) is a genetic disorder caused by mutations in the cystathionine beta synthase gene, which results in impaired metabolism of the sulfur-bearing amino acid homocysteine and its accumulation in blood and tissues. Classical HCU can be detected via newborn screening in the United States, but the test is widely acknowledged to miss many patients. While severely elevated homocysteine levels (>100 μmol /L) frequently lead to a classical HCU diagnosis, intermediate levels (>30 to 100 μmol /L), though linked to many of the known complications of HCU, are not always recognized as associated with HCU. We aimed to identify and describe potentially undiagnosed classical HCU patients using a nationally-representative database of administrative claims and laboratory results. We estimated the national prevalence of patients with homocysteine >30 μmol /L, and compared their demographic and clinical characteristics to those of patients with homocysteine levels ≤30 μmol/L. Among 57,580 patients with a homocysteine test result, 1.8% had a value >30 μmol /L. Patients with homocysteine >30 μmol /L were more frequently diagnosed with hypothyroidism (39.2% vs. 20.7%, p < .001) and renal disease (9.7% vs. 5.5%, p < .001), and were more likely to have a prescription for an anxiolytic/antidepressant (44.5% vs. 38.9%), opioid (58.4% vs. 53.1%), steroid (46.4% vs. 42.5%), or thyroid hormone (38.8% vs. 18.8%), compared to patients with homocysteine ≤30 μmol /L (all p < .05). Both groups were equally likely to have a diagnosis of homocystinuria or another disorder of sulfur-bearing amino acid metabolism (3.8% vs. 4.0%, p = .752). The age-adjusted national prevalence of homocysteine >30 μmol /L was estimated at 33,068 (95% CI: 1033 - 35,104). These findings suggest that thousands of people in the US may be living with intermediate to severely elevated homocysteine levels and may require further evaluation for the presence of classical HCU.

Cystathionine β-synthase deficiency: Of mice and men

Cystathionine β-synthase (CBS) deficiency (Online Mendelian Inheritance in Man [OMIM] 236,200) is an autosomal recessive disorder that is caused by mutations in the CBS gene. It is the most common inborn error of sulfur metabolism and is the cause of classical homocystinuria, a condition characterized by very high levels of plasma total homocysteine and methionine. Although recognized as an inborn error of metabolism over 60years ago, these is still much we do not understand related to how this specific metabolic defect gives rise to its distinct phenotypes. To try and answer these questions, several groups have developed mouse models on CBS deficiency. In this article, we will review various mouse models of CBS deficiency and discuss how these mouse models compare to human CBS deficient patients.

Low bone mineral density is a common finding in patients with homocystinuria

Homocystinuria (HCU) due to deficiency of cystathionine beta-synthetase is associated with increased plasma levels of homocysteine and methionine and is characterized by developmental delay, intellectual impairment, ocular defects, thromboembolism and skeletal abnormalities. HCU has been associated with increased risk for osteoporosis in some studies, but the natural history of HCU-related bone disease is poorly understood. The objective of this study was to characterize bone mineral density (BMD) measured by dual energy X-ray absorptiometry (DXA) in a multi-center, retrospective cohort of children and adults with HCU. We identified 19 subjects (9 males) aged 3.5 to 49.2 years who had DXA scans performed as a part of routine clinical care from 2002-2010. The mean lumbar spine (LS) BMD Z-score at the time of first DXA scan in this cohort was -1.2 (± SD of 1.3); 38% of participants had low BMD for age (as defined by a Z-score ≤-2). Homocysteine and methionine were positively associated with LS BMD Z-score in multiple linear regression models. Our findings suggest that low BMD is common in both children and adults with HCU and that routine assessment of bone health in this patient population is warranted. Future studies are needed to clarify the relationship between HCU and BMD.

High folic acid consumption leads to pseudo-MTHFR deficiency, altered lipid metabolism, and liver injury in mice

BACKGROUND

Increased consumption of folic acid is prevalent, leading to concerns about negative consequences. The effects of folic acid on the liver, the primary organ for folate metabolism, are largely unknown. Methylenetetrahydrofolate reductase (MTHFR) provides methyl donors for S-adenosylmethionine (SAM) synthesis and methylation reactions.

OBJECTIVE

Our goal was to investigate the impact of high folic acid intake on liver disease and methyl metabolism.

DESIGN

Folic acid-supplemented diet (FASD, 10-fold higher than recommended) and control diet were fed to male Mthfr(+/+) and Mthfr(+/-) mice for 6 mo to assess gene-nutrient interactions. Liver pathology, folate and choline metabolites, and gene expression in folate and lipid pathways were examined.

RESULTS

Liver and spleen weights were higher and hematologic profiles were altered in FASD-fed mice. Liver histology revealed unusually large, degenerating cells in FASD Mthfr(+/-) mice, consistent with nonalcoholic fatty liver disease. High folic acid inhibited MTHFR activity in vitro, and MTHFR protein was reduced in FASD-fed mice. 5-Methyltetrahydrofolate, SAM, and SAM/S-adenosylhomocysteine ratios were lower in FASD and Mthfr(+/-) livers. Choline metabolites, including phosphatidylcholine, were reduced due to genotype and/or diet in an attempt to restore methylation capacity through choline/betaine-dependent SAM synthesis. Expression changes in genes of one-carbon and lipid metabolism were particularly significant in FASD Mthfr(+/-) mice. The latter changes, which included higher nuclear sterol regulatory element-binding protein 1, higher Srepb2 messenger RNA (mRNA), lower farnesoid X receptor (Nr1h4) mRNA, and lower Cyp7a1 mRNA, would lead to greater lipogenesis and reduced cholesterol catabolism into bile.

CONCLUSIONS

We suggest that high folic acid consumption reduces MTHFR protein and activity levels, creating a pseudo-MTHFR deficiency. This deficiency results in hepatocyte degeneration, suggesting a 2-hit mechanism whereby mutant hepatocytes cannot accommodate the lipid disturbances and altered membrane integrity arising from changes in phospholipid/lipid metabolism. These preliminary findings may have clinical implications for individuals consuming high-dose folic acid supplements, particularly those who are MTHFR deficient.

Neurologic and neurodevelopmental phenotypes in young children with early-treated combined methylmalonic acidemia and homocystinuria, cobalamin C type

Abnormal neurodevelopment has been widely reported in combined methylmalonic aciduria (MMA) and homocystinuria, cblC type (cblC disease), but neurodevelopmental phenotypes in cblC have not previously been systematically studied. We sought to further characterize developmental neurology in children with molecularly-confirmed cblC. Thirteen children at our center with cblC, born since implementation of expanded newborn screening in New York State, undertook standard-of-care evaluations with a pediatric neurologist and pediatric ophthalmologist. At most recent follow-up (mean age 50 months, range 9-84 months), of twelve children with early-onset cblC, three (25%) had a history of clinical seizures and two (17%) meet criteria for microcephaly. A majority of children had hypotonia and nystagmus. Twelve out of thirteen (92%) underwent neurodevelopmental evaluation (mean age 41 months; range 9-76 months), each child tested with standardized parental interviews and, where possible, age- and disability-appropriate neuropsychological batteries. All patients showed evidence of developmental delay with the exception of one patient with a genotype predictive of attenuated disease and near-normal biochemical parameters. Neurodevelopmental deficits were noted most prominently in motor skills, with relative preservation of socialization and communication skills. Nine children with early-onset cblC underwent magnetic resonance imaging and spectroscopy (MRI/MRS) at mean age of 47 months (range 6-81 months); common abnormalities included callosal thinning, craniocaudally short pons, and increased T2 FLAIR signal in periventricular and periatrial white matter. Our study further characterizes variable neurodevelopmental phenotypes in treated cblC, and provides insights into the etiopathogenesis of disordered neurodevelopment frequently encountered in cblC. Plasma homocysteine and MMA, routinely measured at clinical follow-up, may be poor predictors for neurodevelopmental outcomes. Additional data from large, prospective, multi-center natural history studies are required to more accurately define the role of these metabolites and others, as well as that of other genetic and environmental factors in the etiopathogenesis of the neurologic components of this disorder.

Changes in bone mineral density and body composition of children with well-controlled homocystinuria caused by CBS deficiency

Homocystinuria due to cystathionine β-synthase (CBS) deficiency is an inherited disorder of the metabolism of methionine. Clinical manifestations include mental retardation, dislocation of the optic lens, vascular lesions, arterial and venous thromboembolism, skeletal abnormalities, and osteoporosis. Most homocystinuria patients diagnosed in adulthood have severe osteoporosis, and homocystinuria is frequently mentioned as a cause of osteoporosis. Good control of plasma homocysteine may prevent or delay some of these complications. However, the effectiveness of bone mineral density (BMD) gain or fracture prevention has not been addressed. Here, we describe changes in BMD and body composition in 5 CBS deficiency patients who were diagnosed at young age and were managed with good metabolic control. We found that the BMD of each region was within the normal range. BMD gain was adequate and the patients had no significant change in skeletal morphology.

Selective homocysteine lowering gene transfer improves infarct healing, attenuates remodelling, and enhances diastolic function after myocardial infarction in mice

Background and aims

Homocysteine levels predict heart failure incidence in prospective epidemiological studies and correlate with severity of heart failure in cross-sectional surveys. The objective of this study was to evaluate whether a selective homocysteine lowering intervention beneficially affects cardiac remodelling and cardiac function after myocardial infarction (MI) in a murine model of combined hypercholesterolemia and hyperhomocysteinemia.

Methodology and principal findings

A selective homocysteine lowering gene transfer strategy was evaluated in female C57BL/6 low density lipoprotein receptor (Ldlr)^−/−cystathionine-ß-synthase (Cbs)^+/− deficient mice fed a hyperhomocysteinemic and high saturated fat/high cholesterol diet using an E1E3E4-deleted hepatocyte-specific adenoviral vector expressing Cbs (AdCBS). MI was induced by permanent ligation of the left anterior descending coronary artery 14 days after saline injection or gene transfer. AdCBS gene transfer resulted in a persistent more than 5-fold (p<0.01) decrease of plasma homocysteine levels and significantly improved endothelial progenitor cell function. Selective homocysteine lowering enhanced infarct healing as indicated by a 21% (p<0.01) reduction of infarct length at day 28 after MI and by an increased number of capillaries and increased collagen content in the infarct zone. Adverse remodelling was attenuated in AdCBS MI mice as evidenced by a 29% (p<0.05) reduction of left ventricular cavity area at day 28, by an increased capillary density in the remote myocardium, and by reduced interstitial collagen. The peak rate of isovolumetric relaxation was increased by 19% (p<0.05) and the time constant of left ventricular relaxation was reduced by 21% (p<0.05) in AdCBS MI mice compared to control MI mice, indicating improved diastolic function.

Conclusion/significance

Selective homocysteine lowering gene transfer improves infarct healing, attenuates remodelling, and significantly enhances diastolic function post-MI in female C57BL/6 Ldlr^−/−Cbs^+/− mice. The current study corroborates the view that hyperhomocysteinemia exerts direct effects on the myocardium and may potentiate the development of heart failure.

Combined methylmalonic acidemia and homocystinuria, cblC type. II. Complications, pathophysiology, and outcomes

Combined methylmalonic acidemia and homocystinuria, cblC type, is stated to be the most common inborn error of intracellular cobalamin metabolism. The disorder can display a wide spectrum of clinical manifestations, spanning the prenatal period through late adulthood. While increased homocysteine concentrations and impaired methyl group metabolism may contribute to disease-related complications, the characteristic macular and retinal degeneration seen in many affected patients appears to be unique to cblC disease. The early detection of cblC disease by newborn screening mandates a careful assessment of therapeutic approaches and provides a new opportunity to improve the outcome of affected patients. The following article reviews the current knowledge on the complications, pathophysiology, and outcome of cblC disease in an effort to better guide clinical practice and future therapeutic trials.

Complete deficiency of methylenetetrahydrofolate reductase in mice is associated with impaired retinal function and variable mortality, hematological profiles, and reproductive outcomes

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. We previously characterized BALB/c Mthfr (-/-)mice as a model for this disorder and have recently backcrossed the disrupted allele onto the C57Bl/6 background to examine the variable phenotypes in MTHFR deficiency. Compared with BALB/c Mthfr (-/-)mice, C57Bl/6 Mthfr (-/-)mice have enhanced survival rates (81% vs 26.5%). Four-day-old BALB/c mutant pups had lower body, brain, and spleen weights relative to their wild-type counterparts compared with C57Bl/6 mutants. Pregnant BALB/c Mthfr (+/-)mice had increased resorptions and embryonic delays compared with wild-type littermates, whereas these outcomes in C57Bl/6 c Mthfr (+/-)mice were similar to those of wild-type C57Bl/6 mice. BALB/c-mutant pups had altered hematological profiles (higher hematocrit, hemoglobin, and white blood cell counts, with lower platelet counts) compared with C57Bl/6 mutants. Mutants of both strains had similar degrees of hepatic steatosis, hepatic activity of betaine:homocysteine methyltransferase, and altered cerebellar histology. Electroretinograms (ERG) in C57Bl/6 Mthfr (-/-)mice revealed decreased amplitude of scotopic and photopic waves in 6-week-old mice, with normalized ERGs at 13 weeks. Plasma homocysteine was modestly higher in C57Bl/6 compared with BALB/c mice. Our results emphasize the variable presentation of MTHFR deficiency in different genetic backgrounds and suggest that plasma homocysteine is not a predictor of severity. In addition, our novel findings of decreased spleen weights, thrombocytopenia, and impaired retinal function warrant investigation in patients with severe MTHFR deficiency or other forms of homocystinuria.

Recurrent dystonia in homocystinuria: a metabolic pathogenesis

Dystonia complicating homocystinuria is extremely rare in the absence of thromboembolic disease. We report a unique case of recurrent dystonia in a patient with homocystinuria secondary to pyridoxine-unresponsive cystathionine beta-synthase deficiency. Brain MRI was normal. Two biochemical markers for homocystinuria, homocystine and methionine, were markedly elevated during periods when our patient manifested dystonia. These findings suggest that accumulation of sulfur-containing amino acids may contribute to the pathophysiology of dystonia in patients with homocystinuria.

Homocysteine and large arteries

High plasma concentrations of the amino acid homocysteine have been associated with atherothrombotic disease, first in individuals with inborn errors of homocysteine metabolism, who have very high plasma homocysteine concentrations, and later also in the general population. In general, the cardiovascular risk associated with hyperhomocysteinemia is significant, but modest and probably differs between populations. High homocysteine concentrations are thought to impair endothelial function, increase oxidative stress, impair methylation reactions, and alter protein structure. Although some studies have shown improvement of vascular surrogate end points, homocysteine-lowering treatment has not yet been associated with a significant reduction of cardiovascular events. Studies that have examined the relationship between plasma homocysteine and arterial stiffness parameters have shown heterogenous results.

Clinical and biochemical studies on Chinese patients with methylmalonic aciduria

Methylmalonic aciduria is a common organic aciduria disease. Recently, gas chromatography-mass spectrometry has been used to diagnose methylmalonic aciduria in China. Often, however, the diagnosis of methylmalonic aciduria is delayed because of a lack of technical expertise and the limited experience of general clinicians in China. In this study, the natural history, clinical features, and outcome of 77 Chinese patients with methylmalonic aciduria were investigated. Of the 77 patients, 31 (40.3%) had isolated methylmalonic aciduria and 46 (59.7%) had methylmalonic aciduria combined with homocystinemia. Thus, we observed a higher rate of the combined disease than studies conducted in other countries, suggesting that it might be more common in China. Total plasma homocysteine measurement might enable differential diagnoses of methylmalonic aciduria to be distinguished. The clinical spectrum of these 77 patients with methylmalonic aciduria ranged from neonatal death and severe symptoms to benign asymptomatic organic aciduria. Neonatal and infantile onset, which was a characteristic of the majority of cases, was associated with a greater severity relative to later-onset cases. Among the 17 cases who had onset after 3 years of age, only 1 patient had isolated methylmalonic aciduria and 16 had combined methylmalonic aciduria and homocystinemia. Nine of the patients with combined methylmalonic aciduria and homocystinemia completely recovered and exhibited normal intelligence, whereas seven improved, with a mild handicap.

Homocysteine and endothelial function in human studies

The endothelium plays a key role in the pathophysiology of vascular disease. Impaired flow-mediated dilatation (FMD) is a measure of endothelial dysfunction resulting from reduced bioavailability of nitric oxide (NO). Patients with homocystinuria manifest with impaired FMD, but in mild hyperhomocysteinemia, the evidence is conflicting. Oral loading with methionine or homocysteine impairs FMD, but it remains unproven that this effect is mediated directly by homocysteine. In addition, there is no clear consensus as to a mechanisms by which homocysteine would induce endothelial dysfunction. Folate administration lowers plasma homocysteine and enhances FMD. However, the effect of folate only appears to occur at high doses and with a time course that would indicate that it is acting by a mechanism independent of homocysteine lowering. It is possible that folate, in pharmacological doses, may enhance the NO activity by influencing NO-tetrahydrobiopterin interactions. These studies provide some insights and raise intriguing questions concerning the relationship between homocysteine, folate, and endothelial function. However, changes in FMD may not translate into vascular endpoints, and the outcomes of clinical intervention trials with different doses of folic acid are awaited with interest.

Assessment of visual function in children with methylmalonic aciduria and homocystinuria

The aim of this study was to assess various aspects of visual function in 6 patients (age range: 9 months to 7 years and 8 months) with methylmalonic aciduria and homocystinuria. All patients had an ophthalmological examination and were tested with a battery of age-appropriate tests assessing various aspects of visual function such as acuity, visual fields and visual attention. None of the patients had significant retinal abnormalities but all 6 had nystagmus which was associated with strabismus in 3 of the 6. They all had some abnormalities on the behavioral tests assessing visual function which appeared to be related to the age of the patients. Visual impairment was more severe in the 3 patients below 3 years of age and milder in the older patients. The presence and the severity of abnormalities, in contrast, did not depend on the age at onset or the age when treatment was started and were only partly related to brain MRI findings. Severe hydrocephalus and basal ganglia involvement were associated with severe visual impairment, but abnormal visual findings were also present in the children with normal MRI and isolated mild periventricular changes. Our results suggest that age, brain lesions and other factors may be responsible for visual abnormalities in methylmalonic aciduria and homocystinuria. Further studies using early and sequential assessment of visual function are needed to establish whether the differences observed between younger and older children may be related to the duration of therapy.

Cystathionine beta synthase deficiency promotes oxidative stress, fibrosis, and steatosis in mice liver

BACKGROUND & AIMS

Cystathionine beta-synthase (CBS) deficiency causes severe hyperhomocysteinemia, which confers diverse clinical manifestations, notably liver disease. To investigate this aspect of hyperhomocysteinemia, we performed a thorough investigation of liver pathology in CBS-deficient mice, a murine model of severe hyperhomocysteinemia.

METHODS

The degree of liver injury and inflammation was assessed by histologic examination, by measurements of products of lipid peroxidation, and by formation of carbonyl groups on protein as a measure for the occurrence of protein oxidation. Analysis of profibrogenic, proinflammatory factors and cell apoptosis was performed by Western blots, real-time quantitative reverse-transcription polymerase chain reaction, caspase-3 activity, DNA laddering, and TUNEL assay.

RESULTS

Histologic evaluation of liver specimens of 8- to 32-week-old CBS-deficient mice showed that CBS-deficient mice develop inflammation, fibrosis, and hepatic steatosis, concomitant with an enhanced expression of tissue inhibitor of metalloproteinase-1, alpha-smooth muscle actin, pro(alpha)1 collagen type I, transforming growth factor-beta1, and proinflammatory cytokines. Moreover, even if the proapoptotic protein Bax was dominantly expressed and Bcl-2 was down-regulated, caspase-3 was not activated, DNA laddering was not detected, and number of positive TUNEL cells was not increased in liver of CBS-deficient mice compared with wild-type mice.

CONCLUSIONS

The results show that hyperhomocysteinemia in liver of CBS-deficient mice promotes oxidative stress, which may cause mitochondrial damage in association with activation of hepatic stellate cells, leading to liver injury. The absence of caspase-3 activation, DNA fragmentation, and TUNEL-positive cells shows that protective signals may counteract apoptotic signals in liver of CBS-deficient mice.

Ocular axial length in homocystinuria patients with and without ocular changes: effects of early treatment and biochemical control

PURPOSE

To establish whether myopia in homocystinuria could be due to increased ocular axial length.

METHODS

Measurement of ocular axial length by A-scan ultrasound in eyes of homocystinuria patients.

RESULTS

Patients were divided into three groups. Group I, with no ocular pathology (28 eyes), had mean refractive error of -0.25 D (spherical equivalent) and mean axial length of 23.4 mm +/- 0.9 (+/-1 standard deviation) mm. Group II, with phacodonesis or lens subluxation (12 eyes), had mean refractive error of -10.7 D and mean axial length of 23.8 mm +/-1.9 mm. Patients with phacodonesis had simple myopia whereas those with lens subluxation had marked myopic astigmatism. Group III included patients with complete lens dislocation in at least one eye (12 eyes) and were optically aphakic with a mean refractive error of +12.9 D and mean axial length of 24.9 mm +/- 0.9 mm. All Group I patients had good long-term metabolic control while those in Groups II and III did not. Group III eyes had significantly longer mean axial length than Group I (P =.0018) or normal eyes (P =.0163). There was no statistical difference in mean axial length between Group I and normal eyes.

CONCLUSIONS

Ocular axial length is significantly increased in individuals with homocystinuria and lens dislocation. Increased axial length is a complication that has not been previously described in homocystinuria and may be preventable with early treatment and good biochemical control.

[Homocysteine: why is it harmful?]

This paper discusses the potential pathogenetic mechanisms by which the damaging action of hyperhomocysteinemia on the vessels is realized, namely a negative effect on the structure and function of the vessel wall, on proliferation of smooth muscle cells and endothelium-dependent vasodilatation; on the processes of blood cell interaction with the vessel wall (adhesion of monocytes, platelet adhesion and aggregation, etc): prothrombogenic action on the coagulation system, and effect of homocysteine on adenosine concentration in plasma and tissues.

Inhibition of Na+, K+-ATPase activity by the metabolites accumulating in homocystinuria

Homocystinuria is an inborn error of sulfur amino acid metabolism characterized predominantly by vascular and nervous system dysfunction. In this study we determined the in vitro effects of homocysteine and methionine, metabolites which accumulate in homocystinuria, on Na+, K+-ATPase, and Mg2+-ATPase activities in synaptic membranes from the hippocampus of rats. The results showed that both metabolites significantly inhibit Na+, K+-ATPase but not Mg2+-ATPase activity at concentrations usually observed in plasma of homocystinuric patients. Furthermore, incubation of hippocampal homogenates with homocysteine also elicited an inhibition of the enzyme activity which was however prevented by the simultaneous addition of cysteine to the medium. In addition, cysteine or methionine per se did not modify the two enzymatic activities. These findings indicate that oxidation of critical groups in the enzyme may possibly be involved in homocysteine inhibitory effect. Moreover, kinetic studies performed to investigate the interaction between homocysteine and methionine on Na+, K+-ATPase inhibition suggested a common site for the two amino acids in the enzyme. Considering the critical role exerted by Na+, K+-ATPase in brain, it is proposed that the inhibition provoked by homocysteine and methionine on the enzyme activity may be possibly related to the brain dysfunction characteristic of homocystinuria.

Vitamin C therapy ameliorates vascular endothelial dysfunction in treated patients with homocystinuria

OBJECTIVES

We sought to investigate the effects of short- and long-term vitamin C therapy on endothelial dysfunction in patients with homocystinuria.

BACKGROUND

Untreated homocystinuria due to cystathionine beta-synthase deficiency is associated with premature atherothrombotic disease; 25% of untreated patients suffer a vascular event by the age of 16 years and 50% by 29 years. Treatment directed at reducing homocysteine accumulation significantly reduces this risk. However, despite 'optimal' treatment and compliance, hyperhomocysteinaemia usually persists and individuals exhibit endothelial dysfunction indicative of an adverse cardiovascular prognosis. Additional intervention is therefore required to further reduce cardiovascular risk.

METHODS

We investigated the endothelial effects of acute (2 g single dose) and chronic (1 g/day for 6 months) administration of oral vitamin C in 5 patients with homocystinuria (mean age 26 years, 1 male) and 5 age- and sex-matched controls. Brachial artery endothelium-dependent flow-mediated dilatation (FMD) and endothelium-independent responses to nitroglycerin (NTG) were measured using high-resolution ultrasonic vessel wall-tracking.

RESULTS

Baseline: Plasma total homocysteine was 100.8 +/- 61.6 and 9.2 +/- 1.9 micromol/L in the patient and control groups, respectively (p < 0.001). FMD responses were impaired in the patient group (20 +/- 40 microm) compared with the controls (116 +/- 30 microm) (p < 0.001). Vitamin C administration: FMD responses in the patient group improved both acutely, 160 +/- 65 microm at 4 h (p < 0.001), and chronically, 170 +/- 70 microm at 2 weeks (p < 0.001) and 170 +/- 40 microm at 6 months (p < 0.001). FMD responses in the control group were unaltered (p = 0.526). Within both groups, neither the vascular response to NTG nor plasma homocysteine was altered (p > 0.4).

CONCLUSIONS

Vitamin C ameliorates endothelial dysfunction in patients with homocystinuria, independent of changes in homocysteine concentration and should therefore be considered as an additional adjunct to therapy to reduce the potential long-term risk of atherothrombotic disease.

The controversy over homocysteine and cardiovascular risk

Elevated plasma total homocysteine (tHcy) is a risk factor for occlusive cardiovascular disease (CVD). This concept is based on the observations of premature vascular disease in patients with homocystinuria, the relation between tHcy and both clinical CVD as well as preclinical atherosclerotic disease, the relation between tHcy in children and CVD in their parents or relatives, and reduction in CVD or surrogate endpoints after tHcy-lowering intervention with B vitamins. Plausible mechanisms include the in vivo interference with nitric oxide-dependent reactive vasodilatation. Some observations have raised questions about tHcy as a risk factor. 1) Some prospective studies showed a weak relation or no relation between tHcy and CVD. 2) Several traditional risk factors are associated with tHcy and may confound the relation between tHcy and CVD. 3) tHcy is related to renal function, and hyperhomocysteinemia may reflect early nephrosclerosis. 4) The C677T transition of the methylenetetrahydrofolate reductase gene causes a moderate increase in tHcy but no or only minor increased CVD risk. However, the strength of some of these arguments can be questioned because there is increasing evidence that tHcy is a proximate risk factor provoking the acute event, it strongly interacts with traditional risk factors, and it may predict CVD or death in patients with chronic renal failure. Furthermore, the studies of the C677T polymorphism lack statistical power, and the TT genotype may even modulate CVD risk independently of homocysteine. Thus, only placebo-controlled intervention studies with tHcy-lowering B vitamins and clinical endpoints can provide additional valid arguments for the debate over whether tHcy is a causal CVD risk factor.

[A defense mechanism of human cells in the radioadaptive response and antimutagenic activity of interferon has common paths]

The radioadaptive response was assessed by the chromosome aberration test in lymphocytes of humans with hereditary diseases of connective tissue, which were earlier characterized as repair-deficient: Marfan syndrome (SM), Elers-Danlos syndrome (E-D), and homocystinurea (HCU). The radioadaptive response was observed in cells of patients with Marfan syndrome and Elers-Danlos syndrome but not in cells of patients with homocystinurea. Parameters of cell protection against gamma-irradiation at radioadaptive response were similar to those obtained in cells pretreated with interferon. These data indicate, first, the possibility that repair pathways and the radioadaptive response are independent and second, that there are common pathways of protection upon radioadaptive response and the antimutagenic action of interferon.

Homocystinuria due to cystathionine beta-synthase deficiency in Ireland: 25 years' experience of a newborn screened and treated population with reference to clinical outcome and biochemical control

Homocystinuria (HCU) due to cystathionine beta-synthase deficiency (Mudd et al 1964) was independently described by Gerritsen and colleagues (USA) and Carson and colleagues (Northern Ireland) in 1962. The worldwide frequency of HCU has been reported as 1 in 344,000, while that in Ireland is much higher at 1 in 65,000, based on newborn screening and cases detected clinically. The national newborn screening programme for HCU in Ireland was started in 1971 using the bacterial inhibition assay. A total of 1.58 million newborn infants have been screened over a 25-year period up to 1996. Twenty-five HCU cases were diagnosed, 21 of whom were identified on screening. The remaining four HCU cases were missed and presented clinically; three of these were breast-fed and one was pyridoxine responsive. Twenty-four HCU cases were pyridoxine nonresponsive. Once the status of pyridoxine responsiveness was identified, all pyridoxine nonresponsive cases, but one, were started on a low methionine, cystine-enhanced diet supplemented with pyridoxine, vitamin B12 and folate. Dietary treatment commenced within 6 weeks of birth (range 8-42 days) for those cases detected by screening, while for the late-detected cases treatment was started upon presentation and diagnosis. Biochemical control was monitored measuring deproteinized plasma methionine, free homocystine and cystine at least once a month. Review of the clinical outcome of the 25 HCU cases with 365.7 patient-years of treatment revealed no HCU-related complications in 18 screened, dietary-treated cases. Fifteen of these had lifetime medians of free homocystine < or = 11 mumol/L (range 4-11). The remaining three cases with higher lifetime medians of free homocystine (18, 18 and 48 mumol/L) have developed increasing myopia recently. Among the three screened non-dietary-compliant cases, two have ectopia lentis, one has osteoporosis and two have mental handicap. Of the four cases missed on screening, three presented with ectopia lentis after the age of 2 years. There were no thromboembolic events in any of the 25 HCU cases. The lifetime medians for methionine ranged from 47 to 134 mumol/L. The Irish HCU clinical outcome data suggest that newborn screening, early commencement of dietary treatment and a lifetime median of free homocystine of < or = 11 mumol/L had significantly reduced the probability of developing complications when it was compared to the untreated HCU data (Mudd et al 1985).

Clinical aspects of cystathionine beta-synthase deficiency: how wide is the spectrum? The Italian Collaborative Study Group on Homocystinuria

Homocystinuria due to cystathionine beta-synthase (CBS) deficiency is an autosomal recessive disease of sulphur amino acid metabolism. Major clinical manifestations include disorders of the eye, the skeleton, the central nervous system and the vascular system. A wide clinical spectrum of the disease has been reported. We discuss the role of genetic factors (e.g. different mutations of the CBS gene and a variable genetic background) and the importance of environmental factors (e.g. diet, vitamins, perinatal factors and drugs) in explaining the phenotypic variability observed in homocystinuria.

CONCLUSION

Homocystinuria represents a good model to explain the clinical differences frequently observed among patients affected by monogenic diseases.

Ocular complications and a new surgical approach to lens dislocation in homocystinuria due to cystathionine-beta-synthetase deficiency

The ocular findings in patients with homocystinuria due to cystathionine-beta-synthetase (CBS) deficiency are reviewed and a new approach to lens surgery is presented. Lens surgery in CBS deficiency was reported to be accompanied by a high risk of secondary complications like vitreal prolapse and retinal detachment. So far an operative procedure for these patients that allows a complete preservation of the anterior vitreous cortex, the posterior lens capsule and an implantation of an artificial lens is not established. A minimal invasive method of lens surgery was developed in vitro and applied in the case of a 10-year-old patient with an uncorrectable refractive situation due to progressed lens dislocation. Principle steps of the evolved operative procedure are (1) visco-elastic stabilization of the anterior chamber; (2) small (1.5 mm) peripheral capsulorhexis; (3) manual endocapsular aspiration of lens material and removal of lens epithelium; (4) ab externo introduction of a transcleral fixation suture; (5) positioning of the haptic into the ciliary sulcus in the inferior position; (6) resection of the anterior lens capsule; and (7) positioning of the second haptic into the ciliary sulcus. The first patient treated according to this method presented a stable position of the pseudophakos during the follow up of 1 year. Visual acuity improved from a level of 20/200 (O.D.) and 10/200 (O.S.) to 18/20 in both eyes. The surgical procedure presented in this report seems to be useful for dealing with dislocated lenses due to zonular deficiency in patients with CBS deficiency and hopefully with Marfan disease. It allows a minimal invasive removal of the lens, a complete preservation of the anterior vitreous cortex and at the same time a stable fixation of an artificial intraocular lens.

Biochemical and clinical response to hydroxocobalamin versus cyanocobalamin treatment in patients with methylmalonic acidemia and homocystinuria (cblC)

OBJECTIVE

To compare the therapeutic effectiveness of hydroxocobalamin and cyanocobalamin in patients with combined methylmalonic acidemia and homocystinuria.

STUDY DESIGN

Analysis of urine methylmalonic acid, plasma homocystine, and growth of two unrelated patients with cobalamin C disease who were initially receiving cyanocobalamin and were subsequently switched to hydroxocobalamin.

RESULTS

Each patient had a significant decrease in urine methylmalonic acid excretion while receiving cyanocobalamin, but levels remained at least 10 times normal. Cyanocobalamin treatment resulted in a decrease of plasma homocystine to near normal in one patient but had no effect on plasma homocystine in the second patient. Each patient was switched to hydroxocobalamin and urine methylmalonic acid levels decreased to the limit of detection. Plasma homocystine values while taking hydroxocobalamin remained < 5 nmol/ml in both patients. In patient 1, who continued to receive cyanocobalamin therapy for more than 1 year, growth rates (height, weight, and head circumference) were very poor. After initiation of hydroxocobalamin, growth parameters normalized with growth rates above normal.

CONCLUSION

Intramuscular cyanocobalamin treatment is inadequate in the treatment of patients with cobalamin C disease. Appropriate management of cobalamin C disease should include only the hydroxocobalamin form of cobalamin.

Methionine synthase deficiency without megaloblastic anaemia

We report findings on a child presenting with neonatal homocystinuria, hypomethioninaemia and severe neurological symptoms, including developmental delay and seizures. Methylmalonic aciduria was not present. The activity of methionine synthase in fibroblasts was severely deficient and formation of methylcobalamin from 57Co labelled cyanocobalamin was very low. The patients cells complemented with those of a cblE patient but not with those of two cblG patients. No biochemical or clinical response to injections of hydroxycobalamin was found. Both off treatment and on betaine and methionine supplementation the patient, at age 8 years, has not developed megaloblastic anaemia. In addition, the patient is homozygous for the C677T polymorphism in the 5,10 methylenetetrahydrofolate reductase (MTHFR) gene and the concomitant existence of this mutation with the methionine synthase defect may prevent folate <<trapping>> and thus anaemia.

CONCLUSION

We report the lack of megaloblastic anaemia in a patient with severe methionine synthase deficiency who is also homozygous for C677T in MTHFR, hypothesize that the MTHFR polymorphism protects the patient against anaemia and speculate that homozygosity for MTHFR C677T could cause the dissociation between haematological and neurological disease seen in some patients with vitamin B12 deficiency.

Clinical heterogeneity and prognosis in combined methylmalonic aciduria and homocystinuria (cblC)

The clbC form of methylmalonic acidaemia is a rare and poorly understood condition which results from impaired biosynthesis of methylcobalamin and adenosylcobalamin. The consequent functional deficiencies of methylmalonyl-CoA mutase and methionine synthase produce both methylmalonic aciduria and homocystinuria. Systemic symptoms and neurological decompensation comprise the clinical phenotype. In an effort to clarify the phenotype and prognosis, we obtained clinical information on 50 patients with methylmalonic acidaemia whose cells had been assigned to the cblC complementation group. We identified two distinct phenotypes; they differed in age of onset, presence of systemic symptoms, type of neurological symptoms, and outcome after diagnosis and treatment. Forty-four patients presented in the first year of life. Feeding difficulties, neurological dysfunction (hypotonia, seizures, developmental delay), and ophthalmological and haematological abnormalities characterized their clinical picture. About one-quarter of those patients died. Survival was associated with neurological impairment; only one infant was neurologically intact at follow-up. Onset in childhood, in contrast, was associated with less severe haematological abnormalities, largely involving the red cell series. Extrapyramidal signs, dementia, delirium or psychosis characterized the neurological findings. Survival, with mild to moderate disability in some, was typical in patients with later onset. Treatment in both groups included hydroxycobalamin, betaine and carnitine; complete normalization of biochemical parameters was rare.

Hyperhomocysteinaemia and associated disease

An elevated plasma homocysteine level may result from various environmental and genetic factors. Herediatary causes of severe hyperhomo-cysteinaemia are very rare and usually lead to disease in childhood or adolescence. Common pathology consists of early atherosclerotic vascular changes, arterioocclusive complications and venous thrombosis. Mildly elevated genetically determined plasma homocysteine levels are observed in 5% of the general population. In the last two decades research has shown mild hyperhomocysteinaemia to be linked to an increased risk of premature atherosclerosis, pregnancies complicated by neural tube defects and early pregnancy loss, and venous thrombosis. Homozygosity for thermolabile MTHFR deficiency has been identified as one important genetic factor, which expression is modified by dietary folate intake. Although mild hyperhomocysteinaemia can easily be treated by vitamin supplementation the beneficial effects of such treatment remains to be shown.

Characterisation of five missense mutations in the cystathionine beta-synthase gene from three patients with B6-nonresponsive homocystinuria

Homocystinuria, due to a deficiency of the enzyme cystathionine beta-synthase (CBS), is an inborn error of sulphur-amino acid metabolism. This is an autosomal recessive disease which results in hyperhomocysteinaemia and a wide range of clinical features, including optic lens dislocation, mental retardation, skeletal abnormalities and premature thrombotic events. We report the identification of 5 missense mutations in the protein-coding region of the CBS gene from 3 patients with pyridoxine-nonresponsive homocystinuria. Reverse-transcription PCR was used to amplify CBS cDNA from each patient and the coding region was analysed by direct sequencing. The mutations detected included 3 novel (1058C-->T, 992C-->A and 1316G-->A) and 2 previously identified (430G-->A and 833C-->T) base alterations in the CBS cDNA. Each of these mutations predicts a single amino acid substitution in the CBS polypeptide. Appropriate cassettes of patient CBS cDNA, containing each of the above defined mutations, were used to replace the corresponding cassettes of normal CBS cDNA sequence within the bacterial expression vector pT7-7. These recombinant mutant and normal CBS constructs were expressed in Escherichia coli cells and the catalytic activities of the mutant proteins were compared with normal. All of the mutant proteins exhibited decreased catalytic activity in vitro, which confirmed the association between the individual mutation and CBS dysfunction in each patient.

Clinical and biochemical studies in homocystinuria

Homocystinuria was diagnosed in 15 (0.59%) cases on screening 2560 children for aminoacidopathies. The commonest presenting features were ectopia lentis (95%) and mental retardation (86%). Other features included, dental anomalies (40%), osteoporosis (40%), behavioral problems (33%) and arachnodactyly (13%). Diagnosis was confirmed by iodoplatinate staining of one dimensional paper chromatography of urine. All the 15 cases of homocystinuria were first treated with high dose oral pyridoxine. Only one case responded to pyridoxine therapy. All the other patients were started on a low methionine, High cysteine diet with folate supplementation. Only one patient showed a complete response to dietary therapy. Nonavailability and high cost of the commercially available methionine-free, cysteine-supplemented diet and late diagnosis were responsible for the poor response in the majority of our patients.

Homocysteine and coronary artery disease

BACKGROUND

Homocystinuria is a rare autosomal recessive disease complicated by early and aggressive occlusive arterial disease. This may be related to the grossly increased homocysteine concentrations seen in this disease. More recently, milder hyperhomocysteinemia has been proposed as an independent risk factor for coronary artery disease.

SUMMARY

Many patients with homozygous homocystinuria develop severe premature atherosclerosis and thromboembolism, probably caused by abnormally high concentrations of homocysteine. Homocysteine undergoes metabolism either by remethylation or transsulfuration, and deficiency or dysfunction of any of the substances that regulate these reactions may lead to hyperhomocysteinemia. Homocysteine may have adverse effects on platelets, clotting factors, and endothelial cells. Studies have demonstrated significantly higher plasma homocysteine levels in patients with occlusive arterial disease than in controls. The causes are not clearly understood but may include deficiency of vitamin B6, vitamin B12, and folic acid and heterozygosity for cystathionine synthase deficiency. Vitamin supplementation can lower plasma homocysteine levels.

CONCLUSIONS

Whether measuring plasma homocysteine levels in patients with coronary artery disease should be routine and whether treating hyperhomocysteinemia in these patients may reduce the risk of coronary events remains to be determined.

Anesthetic implications of the child with homocystinuria

We present a 7 1/2-year-old girl with type I homocystinuria who required anesthetic care during repair of bilateral ectopia lentis. Homocystinuria is an autosomal recessive disorder and represents the second most common error of amino acid metabolism. Defective function of the enzyme cystathionine synthetase results in elevated serum levels of methionine and homocysteine. Physiologic disturbances include an increased risk of thromboembolic events and hypoglycemia. Perioperative measures to prevent thromboembolic events include diet therapy to lower serum methionine and homocysteine levels, adequate preoperative hydration, maintenance of intraoperative cardiac output, and the use of pneumatic stockings to prevent peripheral stagnation of blood. Hypoglycemia is thought to be due to alterations in insulin release associated with high levels of circulating sulfur-containing amino acids such as methionine. Perioperative measures include normalization of serum methionine and administration of exogenous glucose during periods of fasting.

[Effect of folic acid for treatment of homocystinuria due to 5,10-methylenetetrahydrofolate reductase deficiency]

Deficiency of 5,10-methylenetetrahydrofolate reductase (MTHFR) leads to deficient remethylation of homocysteine and is one of the causes of homocystinuria. Only 28 patients have been reported so far. A 15-year-old boy with mild mental retardation was admitted in our hospital because of progressive difficulty in walking. He is the second child. The paternal grandparents are first cousins. On admission, clinical examination revealed mild disturbance of consciousness, left hemiparesis, truncal ataxia, pyramidal tract signs in the lower limbs and sensory disturbance in his feet. There was no marfanoid symptoms nor ectopia lentis. EEGs showed slow activity with sporadic spike and wave complexes. Peak latencies of N20 of median nerves SEPs, the third and 5th wave of ABR and P100 of VEP were delayed. The CT scan showed mild cortical atrophy and MRI revealed increased intensity on T2-weighted images in the cerebral white matter. Biochemical studies revealed homocystinuria with homocystinemia. Both plasma methionine and serum folic acid were low. Serum vitamin B12 and methylmalonic acid in urine were normal. The lymphoblastoid cell line, transformed by Epstein-Barr virus of lymphocytes of the patient, could not grow when homocysteine was substituted in the culture medium for methionine. The normal control cell line grew naturally under the same condition. A diagnosis of homocystinuria due to MTHFR deficiency was made. The patient was on various therapeutic regimens for about 70 days. Treatment with high doses of folic acid (400 mg/day) resulted in disappearance of homocysteine in plasma, remarkable decrease of homocysteine in urine and increase of methionine in plasma of the patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired endothelial function occurs in the systemic arteries of children with homozygous homocystinuria but not in their heterozygous parents

OBJECTIVES

Because endothelial dysfunction is an early event in atherogenesis, we aimed to determine whether endothelial function is normal or impaired in the systemic arteries of children with homozygous homocystinuria or in those of heterozygous adults, or both.

BACKGROUND

Homocystinuria is strongly associated with premature vascular disease in homozygotes, and even heterozygotes have been shown to be at increased risk from early atherosclerosis associated with hyperhomocystinemia.

METHODS

We conducted noninvasive studies on the superficial femoral or brachial arteries of 9 children aged 4 to 17 years (mean 11) with homozygous homocystinuria and on the brachial arteries of 14 obligate heterozygous parents age 33 to 49 years (mean 41). Each subject was matched with two control subjects. Using high resolution ultrasound, we measured vessel diameter at rest, during reactive hyperemia (with flow increase causing endothelium-dependent dilation) and after sublingual administration of nitroglycerin (an endothelium-independent vasodilator).

RESULTS

Flow-mediated dilation was observed in the control children (9 +/- 0.6%, range 6% to 14%) but was impaired in the children with homocystinuria (2.8 +/- 0.7%, range 0% to 7%, p < 0.0001). In contrast, nitroglycerin-mediated dilation was similar in both groups (15.7 +/- 1.6% vs. 13.1 +/- 1.2%, p = 0.27), indicating that the impaired flow-mediated dilation is secondary to endothelial dysfunction. In the heterozygous parents, both flow-mediated dilation and nitroglycerin responses (6.3 +/- 0.9%, 17 +/- 1.4%, respectively) were similar to control values (6.8 +/- 0.7%, 20.7 +/- 1.7%, p > 0.10).

CONCLUSIONS

Children with homozygous homocystinuria had impaired endothelial function in the systemic arteries as early as 4 years of age, representing an early event in their premature vascular disease. However, endothelial function was preserved in the heterozygous adults.

Nondetectable electroretinogram in combined methylmalonic aciduria and homocystinuria

We present the case of a patient with congenital methylmalonic aciduria with homocystinuria and a nondetectable electroretinogram. To our knowledge, this is a new entity to be considered in the differential diagnosis of nondetectable electroretinography in infancy.

Functional and morphological deficits in late-treated patients with homocystinuria: a clinical, electrophysiologic and MRI study

Seven late-treated patients between the ages of 10-30 years suffering from homocystinuria were examined clinically and electrophysiologically; four had MRI. The clinical examination showed extrapyramidal features and slight impairment of proprioception. Electrophysiological evaluation revealed normal results in the acoustic and central motor system; a minor, possibly vitamin B6 related, sensory neuropathy was detected by peripheral conduction studies. MR imaging showed small focal areas of gliosis in the white matter, generalized cortical atrophy in two patients, but only one small cortical infarct. No changes in the basal ganglia were detected. These results support the view that neurological signs and symptoms in patients suffering from homocystinuria are related to morphological findings, as well as pharmacological effects.

Homocystinuria and schizophrenia. Literature review and case report

The autosomal recessive disorder homocystinuria involves, in all its subgroups, an abnormality of methionine metabolism. The metabolism of methionine has been a central focus of interest for those who propose the transmethylation hypothesis of schizophrenia. The "methionine effect," as described in the research literature, is thus a theoretical link between these two disorders. The authors review the literature and describe those cases where both have occurred in the same patient. They indicate that whereas many patients with homocystinuria have been psychotic, few have been actually labeled schizophrenic. A patient with homocystinuria, mental retardation, and episodic psychosis is described and this case is used to point to the difficulties in making a definite psychiatric diagnosis in these patients. A relationship between the two syndromes is suggested.

A biological approach to the platelet survival curve with criticism of previous interpretations

The biological mechanisms of platelet destruction must be correctly identified before platelet survival curves can be interpreted. This report develops a theory of platelet destruction which is compared with experiments performed on platelets labelled with the radioactive isotope 51Cr. Platelet destruction rate is a complicated function of platelet number and the thrombokinetic destruction state of the body. A linear approximation of this function shows that destruction is dominated by constant and random consumption. A second order non-linear approximation shows the effect of 'platelet crowding'. This theoretical study explains the difference between predicting the complete platelet survival curve from only two experimental points (in the linear approximation) and the methods of curve fitting currently recommended by the International Committee for Standardization in Haematology. It indicates that the curve fitting of known functional forms to experimental data usually results in an under interpretation of the observations and dilutes the diagnostic potential of the platelet survival curve.

Endothelial cell dysfunction in homocystinuria

This report describes the isolation and culture of venous endothelial cells from the umbilical cord of an obligate heterozygote for homocystinuria. The effect of different sulphur-containing amino acids on the viability and function of these cells was studied and compared with cultured normal endothelial cells. When endothelial cells were cultured in the presence of methionine (10 mmol/l) or homocystine (10 mmol/l), differences occurred between the viability and function of the heterozygote and normal cells in terms of 51Cr release and ability to prevent platelet adherence. The Cr release corrected for spontaneous release increases for the heterozygote cells after incubation/for 21 h in the presence of methionine to 81.3% (control cells, range: 0-23.3%, n = 5) and in the presence of homocystine to 141% (control cells, range: 13.5-55.2%, n = 5). The total number of platelets that adhere to confluent monolayers increases for heterozygote cells cultured in the presence of methionine to 0.98 X 10(7) platelets cm-2 (normal cells, range: 0.56-0.72 X 10(7) platelets cm-2) and in the presence of homocystine to 1.41 X 10(7) platelets cm-2 (normal cells, range: 0.94-1.06 X 10(7) platelets cm-2). Both normal and control cells were sensitive to homocysteine. This study/indicates for the first time what vascular endothelial cells, derived from an obligate heterozygote, are (partly) deficient in cysthathionine synthase and are more susceptible to methionine- and homocystine-mediated injury than normal endothelial cells. Consequently, in homocystinuria, due to dysfunction of the endothelial cells, toxic sulphur-containing amino acids may accumulate in these cells, causing injury of these cells.

Electroencephalographic abnormalities in homocystinuria due to cystathionine synthase deficiency

Nineteen homocystinuric patients--13 children and 6 adults--were identified in the course of a selective screening for homocystinuria due to cystathionine synthase deficiency. Treatment with high doses (300-1200 mg/day) of pyridoxine was carried out in 17 patients, of whom 15 were completely responsive. In 10 patients EEG abnormalities were observed consisting mainly of a mild diffuse non specific slowing of background activity. In two sisters, with no history of seizures, focal paroxymal activity was also recorded. EEG recordings before and after B6 treatment were available in 16 patients, one of whom was a non responder, during treatment seven normal and six abnormal EEGs showed no change whereas three previously abnormal EEGs were classified as normal.