D-2-hydroxyglutaric aciduria: further clinical delineation.

It has recently been recognized that D-2-hydroxyglutaric aciduria is a distinct neurometabolic disorder with a severe and a mild phenotype. Whereas the clinical and neuroimaging findings of the severe phenotype were homogeneous among the patients, the findings in the mild phenotype were much more variable, leaving the clinical picture poorly defined. We were able to collect the clinical, biochemical and neuroimaging data on an additional 8 patients with D-2-hydroxyglutaric aciduria, 4 with the severe and 4 with the mild phenotype. With the new information, it becomes clear that the mild phenotype shares the essential characteristics of the severe phenotype. The most frequent findings, regardless of the clinical phenotype, are epilepsy, hypotonia and psychomotor retardation. Additional findings, mainly occurring in the severe phenotype, are episodic vomiting, cardiomyopathy, inspiratory stridor and apnoeas. The most consistent MRI finding is enlargement of the lateral ventricles, occipital more than frontal. Regardless of the clinical phenotype, early MRI shows in addition subependymal cysts and signs of delayed cerebral maturation. Later MRI may reveal multifocal cerebral white-matter abnormalities. Two patients had vascular abnormalities, but it is as yet unclear whether these are related to D-2-hydroxyglutaric aciduria or are incidental findings.

[Molecular genetics of the remethylation of homocysteine]. / Génétique moléculaire de la reméthylation de l'homocystéine.

In plasma of mothers with a child affected with a neural tube defect plasma homocysteine is often elevated, and attributed to a reduced folate-dependent homocysteine remethylation. There is strong evidence that folic acid prevents fasting moderate hyperhomocysteinemia. The pathophysiology of neural tube defect and interactions between genetic and nutritional factors that determine plasma homocysteine levels remain poorly understood. Investigations on genetic causes of moderate hyperhomocysteinemia are in progress. This mini-review focuses on molecular genetic knowledge of folate-dependent homocysteine remethylation in neural tube defect.

Homocysteine, hypothyroidism, and effect of thyroid hormone replacement.

Elevation of total plasma concentration of homocysteine (t-Hcy) is an important and independent risk factor for cardiovascular disease. Hypothyroidism is possibly also associated with an increased risk for coronary artery disease, which may be related to atherogenic changes in lipid profile. Because hypothyroidism decreases hepatic levels of enzymes involved in the remethylation pathway of homocysteine, we prospectively evaluated fasting and postload t-Hcy in patients before and after recovery of euthyroidism. Fasting and postload t-Hcy levels were higher in 40 patients with peripheral hypothyroidism (14 with autoimmune thyroiditis and 26 treated for thyroid cancer) in comparison with those of 26 controls (13.0 +/- 7.5 vs. 8.5 +/- 2.6 micromol/L, p < .01, respectively, and 49.9 +/- 37.3 vs. 29.6 +/- 8.4 micromol/L p < .001, respectively). On univariate analysis, fasting Hcy was positively related to thyrotropin (TSH) and inversely related to folates. Multivariate analysis confirmed TSH as the strongest predictor of t-Hcy independent of age, folate, vitamin B12, and creatinine. Thyroid hormone replacement significantly decreased fasting but not postload t-Hcy. We conclude that t-Hcy is elevated in hypothyroidism. The association of hyperhomocysteinemia and lipid abnormalities occurring in hypothyroidism may represent a dynamic atherogenic state. Thyroid hormone failed to completely normalize t-Hcy. Potential benefit of treatment with folic acid in combination with thyroid hormone replacement has to be tested given that hypothyroid patients were found to have lower levels of folate.

[Cerebral vascular complication of hyperhomocysteinemia. Controlling thromboembolic complications with folates]. / Accident vasculaire cérébral avec hyperhomocystéinémie. Arrêt des accidents thromboemboliques sous folates.

BACKGROUND: Young patients who experience cardiovascular events may have raised levels of homocysteine. There may be several causes for this hyperhomocysteinemia. CASE REPORT: Cerebrovascular disease occurred in a 40-year-old female smoker with hyperhomocysteinemia. This patient subsequently had several episodes of thromboembolism involving the brain and lower limb arteries. Prothrombin concentration was difficult to control with antivitamin K anticoagulants. Investigations to identify a genetic cause of hyperhomocysteinemia revealed that she was homozygous for the C677T mutation on the methylenetetrahydrofolate reductase gene. There was no G1691A mutation of the factor V gene, a risk factor for familial thrombosis. Supplementation with folic acid successfully halted episodes of thromboembolism (follow-up 2 years) and prothrombin levels stabilized under treatment. DISCUSSION: The C677T mutation, which is common in the general population (15.7%), cannot explain the effect of folate supplementation alone. Other mutations affecting homocysteine metabolism could have a potentializing effect on vascular events.

Fatal neonatal liver failure and mitochondrial cytopathy (oxidative phosphorylation deficiency): a light and electron microscopic study of the liver.

Mitochondrial cytopathies are multisystemic disorders of extremely variable expression due to a deficiency in oxidative phosphorylation. Cases have recently been reported in which fatal liver failure with neonatal onset was the major clinical and biochemical syndrome. In this series we reviewed the liver histology of 10 such patients who died in the first weeks of life (from 3 days to 6 mo). In six cases the diagnosis was confirmed by study of the mitochondrial respiratory chain in the muscle, liver or both; in the other four, appropriate tests were not available for diagnosis but symptoms were identical and all other diagnoses were ruled out. In all 10 cases we noted significant steatosis, mostly microvesicular; widespread hepatocytic, canalicular and bile duct cholestasis with bile thrombi and cholangiolar proliferation; and different degrees of hepatosiderosis and glycogen depletion. Fibrosis took varying forms: perisinusoidal, periportal with the formation of septa, even precirrhosis. In the two cases of infants who died, one at 5 and one 6 mo, micronodular cirrhosis was also present. Mitochondria, either densely or loosely packed, were abnormal-pleiomorphic with few or no cristae and a granular fluffy matrix. Dense, large granules were seen in two cases. The association of neonatal liver failure and hyperlactacidemia should lead to immediate examination of the respiratory chain. The expression of this mitochondrial cytopathy can be lethal, associated with severe liver damage due to the deficiency in oxidative phosphorylation.

[Coffin-Lowry syndrome and hyperprolinemia]. / Syndrome de Coffin-Lowry et hyperprolinémie.

BACKGROUND: The main features of the Coffin-Lowry syndrome are mental retardation and features of a peculiar pugilistic nose, large ears, tapered fingers, drumstick terminal phalanges by X-rays and kyphoscoliosis. Inheritance is probably X-linked dominant. Its early diagnosis is difficult. CASE REPORT: A 31 month-old boy was admitted for mental retardation. His weight and height were normal, but his facies showed telecanthus, anteverted nares and a prominent frontal region. His hands appeared puffy with bulbous tapering fingers. Amino-acid chromatography showed hyperprolinemia (732 mumol/l) plus iminoglycinuria. His mother had a short stature, mental retardation and similar, although minor, manifestations of the Coffin-Lowry syndrome in her face, hands and fingers. She had moderate hyperprolinemia (391 mumol/l) without hyperglycinuria. The patient's father showed no physical abnormalities, but he also had hyperprolinemia (671 mumol/l) and hyperglycinuria. CONCLUSION: The association of the Coffin-Lowry syndrome and hyperprolinemia in this family seems fortuitous.

Fatal neonatal liver failure and mitochondrial cytopathy: an observation with antenatal ascites.

Mitochondrial cytopathies are multisystemic diseases of extremely variable expression caused by a deficiency in oxidative phosphorylation. Only five cases of neonatal liver failure in the context of mitochondrial cytopathy have been reported, with incomplete morphological data of the liver in three. In the case presented here, ascites had been diagnosed prenatally and liver failure was particularly severe (factor V less than 15% with fatal coma the fourth day). Histologically there were incomplete cirrhosis, microvesicular steatosis, major canalicular cholestasis with proliferative neocholangioles, and bile duct thrombi. There were also some iron pigments in the periportal area and partial glycogen depletion. By electron microscopy, mitochondria in numerous hepatocytes appeared abnormal with occasional cristae in a fluffy matrix, some containing dense inclusions. Study of respiratory chain activity showed a defect in cytochrome c oxidase (complex IV), revealed by oxygraphic measurement on fresh muscle biopsy and confirmed by spectrophotometric enzymatic assays performed on muscle and liver homogenates. The association of neonatal liver failure with hyperlactacidemia warrants investigation into a deficiency in oxidative phosphorylation.

Mitochondrial myopathy studies on permeabilized muscle fibers.

Respiratory parameters of skeletal muscle were determined in permeabilized muscle fibers by adapting a technique described by Veksler et al. for cardiac fibers (Biochim Biophys Acta, 892:191-196, 1987). This method consists of the permeabilization of muscle fibers by saponin by allowing respiratory substrates and inhibitors to reach the mitochondria. In this way, the mitochondria may be studied inside the fibers as if they were isolated. We have verified, using various techniques, that the mitochondria remain intact during this procedure. This method has been applied to the study of six newborn infants for whom a diagnosis of a mitochondrial defect was suspected. In all cases, the defect was to be found on the permeabilized fibers, and this was confirmed by an enzymatic study. The advantage of this new method, associated with the measurement of the enzymatic activities on a crude homogenate, is to enable a simple and rapid diagnosis on a small amount of sample without damaging the mitochondria during the isolation procedure.

[Beta-ketothiolase deficiency: a case of ketoacidosis with hyperglycinemia]. / Déficit en bêta cétothiolase: un cas d'acidocétose avec hyperglycinémie.

Regarding a case of beta-ketothiolase deficiency revealed by ketoacidosis with hyperglycinemia, the authors show the way to diagnose and to treat this disease. Ketoacidosis without hyperglycemia or lactacidemia suggested this diagnosis. Gas chromatography-mass-spectrography revealed unusual urinary excretion of metabolic products of isoleucine. The enzymological study of fibroblasts confirmed the diagnosis. The treatment of acute episodes consisted of acidosis control and exclusive glucides intake before diagnosis. Afterwards, a controlled proditic diet and L-carnitine must be given and fasting must be avoided.