Characterization and review of MTHFD1 deficiency: four new patients, cellular delineation and response to folic and folinic acid treatment.

In the folate cycle MTHFD1, encoded by MTHFD1, is a trifunctional enzyme containing 5,10-methylenetetrahydrofolate dehydrogenase, 5,10-methenyltetrahydrofolate cyclohydrolase and 10-formyltetrahydrofolate synthetase activity. To date, only one patient with MTHFD1 deficiency, presenting with hyperhomocysteinemia, megaloblastic anaemia, hemolytic uremic syndrome (HUS) and severe combined immunodeficiency, has been identified (Watkins et al J Med Genet 48:590-2, 2011). We now describe four additional patients from two different families. The second patient presented with hyperhomocysteinemia, megaloblastic anaemia, HUS, microangiopathy and retinopathy; all except the retinopathy resolved after treatment with hydroxocobalamin, betaine and folinic acid. The third patient developed megaloblastic anaemia, infection, autoimmune disease and moderate liver fibrosis but not hyperhomocysteinemia, and was successfully treated with a regime that included and was eventually reduced to folic acid. The other two, elder siblings of the third patient, died at 9 weeks of age with megaloblastic anaemia, infection and severe acidosis and had MTFHD1 deficiency diagnosed retrospectively. We identified a missense mutation (c.806C > T, p.Thr296Ile) and a splice site mutation (c.1674G > A) leading to exon skipping in the second patient, while the other three harboured a missense mutation (c.146C > T, p.Ser49Phe) and a premature stop mutation (c.673G > T, p.Glu225*), all of which were novel. Patient fibroblast studies revealed severely reduced methionine formation from [(14)C]-formate, which did not increase in cobalamin supplemented culture medium but was responsive to folic and folinic acid. These additional cases increase the clinical spectrum of this intriguing defect, provide in vitro evidence of disturbed methionine synthesis and substantiate the effectiveness of folic or folinic acid treatment.

Spectrum of chronic lung disease in a population of newborns with extremely low gestational age.

AIMS: To determine how the ability to oxygenate the blood develops after birth in infants of extremely low gestational age (ELGANs) and to find risk factors for chronic lung disease. METHOD: A prospective, population-based, cohort study was undertaken in one tertiary-care centre. The alveolar-arterial oxygen pressure difference (AaDO(2)) was monitored. RESULTS: Of 41 survivors, 21 had a period of normal lung function in the first week of life, after which oxygenation deteriorated. Low gestational age and low Apgar score at 5 min were found to be strong and independent predictors of AaDO(2) in the first month of life. Mechanical ventilation did not appear as a risk factor. Lung function at 36 weeks of gestation and duration of oxygen treatment could be better predicted by the severity of lung disease in the first month than by gestational age at birth. CONCLUSIONS: Difficulty in oxygenation was a general observation in ELGANs and not only a particular subset. Gestational age and Apgar score were independent predictors of the degree of difficulty over the first month of life. As oxygenation failure often developed after a few days, the process may be possible to treat or prevent once the pathogenesis is known.

Identification of unusual 7-oxygenated bile acid sulfates in a patient with Niemann-Pick disease, type C.

Niemann-Pick disease, type C, was diagnosed in a 3-month-old boy with hepatosplenomegaly, mild signs of cholestasis, hepatic inflammation and extramedullary erythropoiesis, together with chronic airway disease. He developed muscular hypotonia, psychomotor retardation, rickets, and signs of peripheral neuropathy. The patient was found to excrete abnormal amounts of unusual bile acids in urine at 3 and 5 months of age. These acids were shown to have a 3beta-hydroxy-Delta(5) structure and to carry an oxo or hydroxy group at C-7. They were sulfated at C-3 and nonamidated or conjugated with glycine or taurine at C-24. Part of the 7-hydroxy acids, presumably the 7beta-hydroxylated one, was also conjugated with N-acetylhexosamine, probably N-acetylglucosamine, at the 7-hydroxy group. Possible metabolic pathways for the formation of the 7-oxo and 7beta-hydroxycholenoic acids are discussed. Based on previous data concerning the effects of 3beta-hydroxy-Delta(5) bile acids on bile acid transport, it is suggested that the formation of such bile acids is responsible for the cholestasis in this patient.

D-2-Hydroxyglutaric aciduria: biochemical marker or clinical disease entity?

D-2-Hydroxyglutaric aciduria has been observed in patients with extremely variable clinical symptoms, creating doubt about the existence of a disease entity related to the biochemical finding. An international survey of patients with D-2-hydroxyglutaric aciduria was initiated to solve this issue. The clinical history, neuroimaging, and biochemical findings of 17 patients were studied. Ten of the patients had a severe early-infantile-onset encephalopathy characterized by epilepsy, hypotonia, cerebral visual failure, and little development. Five of these patients had a cardiomyopathy. In neuroimaging, all patients had a mild ventriculomegaly, often enlarged frontal subarachnoid spaces and subdural effusions, and always signs of delayed cerebral maturation. In all patients who underwent neuroimaging before 6 months, subependymal cysts over the head or corpus of the caudate nucleus were noted. Seven patients had a much milder and variable clinical picture, most often characterized by mental retardation, hypotonia, and macrocephaly, but sometimes no related clinical problems. Neuroimaging findings in 3 patients variably showed delayed cerebral maturation, ventriculomegaly, or subependymal cysts. Biochemical findings included elevations of D-2-hydroxyglutaric acid in urine, plasma, and cerebrospinal fluid in both groups. Cerebrospinal fluid gamma-aminobutyric acid was elevated in almost all patients investigated. Urinary citric acid cycle intermediates were variably elevated. The conclusion of the study is that D-2-hydroxyglutaric aciduria is a distinct neurometabolic disorder with at least two phenotypes.

Impaired gas mixing and low lung volume in preterm infants with mild chronic lung disease.

The aim of this study was to assess the possible role of gas mixing inefficiency in spontaneously breathing infants with mild chronic lung disease (CLD) of prematurity in relation to changes in other functional parameters. A simple bedside technique for recording and analysis of multiple breath nitrogen washout curves was applied together with occlusion mechanics. Fifteen preterm infants with mild or moderately severe CLD were studied at a mean postconceptional age of 35 wk, together with 15 healthy preterm infants at the same maturity. All infants breathed spontaneously, and the test was performed by a continuous bypass flow system, connected to a face mask, a pneumotachograph, and a nitrogen meter. The results showed impaired gas mixing with moment ratios above the 95th percentile of the normal group in 11/15 infants with CLD. Functional residual capacity (FRC) was low in 13/15 infants, but specific compliance and resistance of the respiratory system did not differ between the groups. As FRC and moment ratios were not correlated, it is suggested that they may reflect different aspects of the pathophysiology in CLD. It is concluded that low FRC and disturbed gas mixing are characteristic disturbances in CLD at different degrees of severity. The multiple breath nitrogen washout test, followed by moment analysis of end-tidal nitrogen concentrations, is a simple and sensitive method for detection of these disturbances and for monitoring purposes.

Moment analysis of multibreath nitrogen washout in healthy preterm infants.

Moment analysis (MA) of multibreath nitrogen washout (MBNW) has not previously been applied to newborn infants. The aim of the present study was to adapt this method to healthy preterm infants using an improved technique suitable for small infants, and to determine reference values of MA. Twenty healthy preterm infants with a mean birth weight (+/-SD) of 1,666+/-402 g and a mean gestational age of 31.3+/-2.1 weeks were studied during their first 7-28 days of life. Computerized bedside equipment with very low dead space was constructed. The limits of normal variability were determined from results of duplicate studies. Outcome variables included functional residual capacity (FRC), the first-to-zeroth moment ratio (M1/M0), the second-to-zeroth moment ratio (M2/M0), and the lung clearance index (LCI). The starting point for MA had considerable impact on the results. Mean M1/M0 and M2/M0 were 2.18+/-0.18 and 8.71+/-1.24, respectively. No significant relation between moment ratios and weight, gender or age was found. Intrasubject coefficients of variation (CV) for M1/M0 (7.9+/-5.9%) and for M2/M0 (12.1+/-9.1%) and intersubject CV for M1/M0 (8%) and M2/M0 (14%) were similar to those reported in children and adults. Mean lung clearance index was 10.8+/-1.4 and intra- and intersubject CVs were 11.3+/-8.9% and 13%, respectively. Mean functional residual capacity (FRC) was 22.5+/-2.1 ml/kg. Mean intra- and intersubject CVs for FRC were 8.3% and 9%, respectively. We conclude that the MBNW test can be performed by a simple bedside method and that MA appears to be a suitable method for measuring gas mixing in preterm infants.

Lung function testing--useless in ventilated newborns?

Several methods have been used for lung function testing in the ventilated newborn. The interest in the field has been stimulated by the recent appearance of commercially available equipment for assessment of mechanical parameters and of functional residual capacity in this group. Nevertheless, lung function testing is rarely used as a clinical routine, even such simple variables as tidal volume and minute ventilation. Among the many possible reasons for this condition, the fragile nature of the infants and the hands-off policy usually exercised, the difficulties in measuring flow accurately, and the complexity of the present methods deserve special attention. In order to change this situation more work needs to be done to elucidate basal physiology of the ventilated lung and the relationships between ventilator settings, lung function and side-effects in different conditions. If then sufficiently simple, safe and accurate methods to assess the most important functions can be offered, lung function testing would be likely to become a useful component of routine care in future neonatal intensive care.

Treatment of hereditary tyrosinaemia type I by inhibition of 4-hydroxyphenylpyruvate dioxygenase.

Liver transplantation is the only effective treatment for hereditary tyrosinaemia type I (McKusick 276700). We have treated one acute and four subacute-chronic cases with 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC), a potent inhibitor of 4-hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27), to prevent the formation of maleylacetoacetate and fumarylacetoacetate and their saturated derivatives. The oral daily dose was 0.1-0.6 mg/kg. The excretion of succinylacetoacetate and succinylacetone decreased from 15-103 mmol/mol creatinine to the detection limit or slightly above (ie, to 20-150 mumol/mol creatinine). The concentration of succinylacetone in plasma decreased from 5.8-43 mumol/l to the detection limit (0.1 mumol/l) over 2-5 months of treatment. The almost complete inhibition of porphobilinogen synthase in erythrocytes was abolished and the excretion of 5-aminolevulinate decreased to within or slightly above the reference range. The concentration of alpha-fetoprotein decreased in four patients to 1.3-7.5% of initially high values over 6-8 months. Improved liver function was reflected by normal concentrations of prothrombin complex and in decreased activities of alkaline phosphatase and gamma-glutamyltransferase in serum. Computed tomography revealed regression of hepatic abnormalities in three patients. One patient developed rickets 6 months before treatment and had excreted high concentrations of markers of tubular dysfunction--after 3 weeks of treatment, this excretion had disappeared. No side-effects were encountered. Inhibition of 4-hydroxyphenylpyruvate dioxygenase may prevent the development of liver cirrhosis and abolish or diminish the risk of liver cancer. Normalisation of porphyrin synthesis will eliminate the risk of porphyric crises. This type of treatment may thus offer an alternative to liver transplantation in hereditary tyrosinaemia.

Lung volume, gas mixing, and mechanics of breathing in mechanically ventilated very low birth weight infants with idiopathic respiratory distress syndrome.

We assessed pulmonary function in 14 mechanically ventilated newborn very low birth weight infants with idiopathic respiratory distress syndrome by means of a face-out, volume displacement body plethysmograph and nitrogen washout analyses. Specially designed computer programs were used for calculations of lung volumes, ventilation, gas mixing efficiency, and mechanical parameters. In addition to very low compliance and moderately elevated resistance of the respiratory system, there were considerably impaired gas mixing efficiency and low functional residual capacity (FRC). No correlations between positive end-expiratory pressure and mean airway pressure versus compliance, resistance, or FRC could be found. Neither could correlations be found between FRC and compliance or FRC and the calculated right to left shunt.

A plethysmographic method for assessment of lung function in mechanically ventilated very low birth weight infants.

We have developed and tested a plethysmographic method for assessment of lung function in mechanically ventilated very low birth weight infants during intensive care. Information about the mechanics of the respiratory system is obtained from the respiratory flow as measured by volume displacement plethysmography and from airway pressure measured in the artificial airway. Data on lung volumes, ventilation, and distribution of ventilation is obtained simultaneously by combining the respiratory flow measurements with nitrogen concentration analyses of the respiratory gas. No significant differences were found when the estimations of mechanical parameters and FRC were compared with reference methods and when determinations of the same parameters were repeated in the same subjects. The plethysmograph was shown to be safe and convenient to use, even in studies lasting several hours.

Immediate effects on lung function of instilled human surfactant in mechanically ventilated newborn infants with IRDS.

We have studied the effects on lung volume, respiratory mechanics and ventilation during the first hours after instillation of 60 mg/kg of human surfactant into the trachea of 4 very preterm, newborn infants with severe IRDS under mechanical ventilation. Measurements were made with a "face-out" body plethysmograph and a modified nitrogen wash-out method. In addition to a transient decrease in total and alveolar ventilation immediately after the instillation we found an immediate rise in lung volume, but respiratory compliance decreased. These changes lasted less than two hours. Oxygen requirements fell in 3 out of 4 infants. The changes in lung volume and compliance are explained in terms of changes in the shape of the static recoil pressure characteristics of the diseased lungs after treatment. Mechanisms behind the short duration are sought in mode of instillation, dosage, age at treatment, and severity of disease.

Mitochondrial myopathy and cardiomyopathy in siblings.

Two siblings with infantile lactic acidosis and mitochondrial myopathy are described. The first child, a girl, died at 5 months of age from severe lactic acidosis after about 3 weeks of progressive muscular hypotonia. The younger brother had congenital lactic acidosis but no other symptoms until 6 months of age when progressive muscle weakness appeared. Treatment with dichloroacetate lowered the serum lactic acid level but did not affect his clinical condition. At 13 months of age, cardiomyopathy was diagnosed and he died at the age of 29 months of circulatory failure. Both children had mitochondrial myopathy. Postmortem examination of the boy revealed marked morphologic changes of the mitochondria in both skeletal muscle and the myocardium; biochemical investigation of skeletal muscle mitochondria demonstrated deficiencies in both complex I (NADH ferricyanide reductase) and complex IV (cytochrome c oxidase). The disease in these siblings differs in several respects from previously reported patients with mitochondrial myopathy and cytochrome c oxidase deficiency.

Lung function in newborn infants with tachypnea of unknown cause.

Twenty-one infants with tachypnea (f greater than 60/min) lasting more than 2 h and diagnosed as mild respiratory disease or pulmonary maladaptation according to previously presented criteria were studied during the course of the disease and after clinical recovery. Lung physiology (total and alveolar ventilation, efficiency and distribution of ventilation, functional residual capacity, and lung mechanics) was studied in combination with clinical data. The pathophysiological findings were characterized by increased total ventilation but normal alveolar ventilation, reduced efficiency of ventilation but more even distribution of ventilation (nitrogen elimination pattern) during disease than after clinical recovery, hyperinflation, reduced dynamic lung compliance but unaffected specific lung conductance. Infants with low gestational ages were most severely affected and had longer duration of disease than full-term infants. Our findings suggest that this condition is caused by small airway disease. Disturbances in normal pulmonary adaptation with abnormal retention of lung fluid is the most probable cause.

Need of hospital care for newborn infants. A population analysis of preterm infants and infants with respiratory disturbances.

In a prospective study of a total population the hospital resources required for the care of preterm infants and infants with respiratory disturbances (RD) were analyzed. 5.2% of all the infants were preterm and 7.6% developed RD. For the care of preterm infants the requirements were 63.8 beds per 1,000 annual preterm births of which 8.3 beds were attributable to the care of RD in these infants. Full term infants needed 0.88 hospital beds per 1,000 annual full term births for respiratory care. The number of days on ventilator for preterms was calculated to 2,044 per 1,000 annual preterm births. For preterm infants the mode of delivery was not found to affect the length of hospitalization. For the total population the average need of hospital days for full term infants because of RD was 0.29 days after vaginal delivery compared with 0.78 days after elective Caesarean section.

Efficiency of ventilation in neonatal pulmonary maladaptation.

Lung physiology was studied in sixteen infants with pulmonary maladaptation (PMA) during the course of the disease and after clinical recovery. A sensitive nitrogen washout method was used. During the disease the infants showed reduced ventilatory efficiency and increased dead space. Total ventilation increased simultaneously, while alveolar ventilation was maintained. The majority of the infants showed greater functional residual capacity during the disease than after clinical recovery. The results suggest that gas mixing efficiency is impaired in infants with PMA and that this might be due to effects on the small airway function in the lungs.

Low Apgar score as a risk factor for respiratory disturbances in the newborn infant.

The value of the Apgar score as a risk factor for all neonatal respiratory disturbances (RD) was evaluated in a prospective study of an unselected population. All liveborn infants (n = 4656) of mothers living in Gothenburg were screened over one year for signs of respiratory disease. This unselected population could be obtained since virtually all infants in Gothenburg are born in two maternity hospitals, with similar treatment principles, the same equipment standard and neonatal care. A low one minute Apgar score (less than 7) was found to be a powerful risk factor for RD in full term newborns and infants of 33-36 weeks gestation provided that the delivery had been vaginal. In these infants a low Apgar score at five minutes further increased the risk of RD. In immature infants less than 32 weeks and after cesarean section in all gestational ages a low Apgar score did not mean any additional risk of RD. The respiratory component in the Apgar score was not more predictive of RD than any of the others. In most infants with RD, irrespective of Apgar score, there was a few hours interval free from respiratory signs after birth. It has been well shown in other studies that Apgar score is not a reliable index of intrauterine or birth asphyxia. Nevertheless the one-minute score is a powerful predictor of neonatal respiratory difficulties. One explanation might be that Apgar score is correlated with sympathoadrenal activity at birth.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidemiological analysis of the increased risk of disturbed neonatal respiratory adaptation after caesarean section.

In a prospective, unselected study of all 4,659 infants born in Göteborg, Sweden, risk factors for all kinds of neonatal respiratory disturbances (RD) after Caesarean section (CS) were analyzed. After CS, a significantly increased incidence rate of RD was found compared to vaginal delivery (24.6% vs. 5.5%). The increased overall risk affected full term infants only but IRDS was more common after CS in preterm infants. Rupture of membranes or uterine contractions prior to CS significantly reduced the incidence rate of RD in full term infants. Acute maternal complications did not affect the incidence. The elevated RD rate could partly be related to an increased incidence of low Apgar score after CS, and to absence of labour and rupture of membranes before the CS. But full term infants with Apgar score of 7 or more, delivered surgically after rupture of membranes and start of contractions, still had almost three times higher incidence of RD.

Interval from rupture of the membranes to delivery and neonatal respiratory adaptation.

The influence of the time interval from rupture of the membranes to delivery on neonatal respiratory adaptation was analysed in a prospective study of all infants born in Göteborg, Sweden in one year. The correlation between the incidence of respiratory disorders and the rupture-delivery interval was analysed in all preterm infants (less than or equal to 36 weeks, n = 240) and in all term infants born by caesarean section (n = 452). A uniform pattern was found for all preterm infants, irrespective of mode of delivery, and for the term infants born by caesarean section. The curve was 'U-shaped' with higher incidence of respiratory diseases in infants born immediately after rupture of the membranes than in those born 3-36 h after membrane rupture. The incidence increased again in infants born greater than 36 h after membrane rupture. The same pattern was found for all kinds of respiratory diseases including idiopathic respiratory distress syndrome. Therefore, there seems to be no advantage in postponing delivery greater than 36 h after rupture of the membranes.