Neonatal screening for biotinidase deficiency in East-Hungary

Summary There are two types of multiple carboxylase deficiency, the neonatal form with holocarboxylase synthetase defect and the late-onset form with biotinidase deficiency. We report our preliminary experiences in screening for biotinidase deficiency. In total 43 493 infants were screened for the deficiency of the enzyme biotinidase; 0.14% false positive results that necessitated requests for second blood samples and two newborns with a biotinidase defect were identified during our pilot study. The definitive diagnosis required the demonstration of enzyme deficiency in serum. Both of the patients have residual biotinidase activity: 3.59% and 7.55%. These two newborns with biotinidase deficiency are treated with daily supplementation of free biotin. According to our preliminary results biotinidase deficiency satisfies all the criteria for incorporation into the national newborn mass screening.     

Comparison of patients with complete and partial biotinidase deficiency: Biochemical studies

Summary Seventeen partially biotinidase-deficient patients detected by neonatal screening or family studies were compared with four patients with classical biotinidase deficiency. Using a sensitive HPLC method for biotinidase in plasma (substrate: biocytin) the patients could be divided into two groups: one with residual biotinidase activity, and the second with undetectable biotinidase activity (0-activity). Biocytin excretion, characteristically elevated in 0-activity patients, decreased rapidly with increasing residual biotinidase activity and was almost normal when residual activity exceeded 2–3% of mean normal. In one patient with classical disease (0-activity) biotin deficiency, typical organic aciduria and multiple carboxylase deficiency were found as early as at the second week of life. In contrast, 13 infants with residual activities from 1.2% to 23% had no remarkable clinical or biochemical abnormalities. However, in three 5-, 14- and 15-year-old healthy siblings with residual biotinidase activities between 2.3% and 4.2%, biotin deficiency was proven by decreased activities of the mitochondrial carboxylases in lymphocytes (30–57% of mean normal) and, in the older siblings, also by subnormal plasma biotin concentrations. In biotinidase deficiency, biotin depletion presumably occurs earlier in the brain than in other tissues and may thus first affect the central nervous system. For this reason and because of discrete biochemical abnormalities found in a patient with residual biotinidase activity of 8%, we suggest that at least all patients with residual activities below 10% should be treated with biotin.Presented as poster and abstract (P145) at the 26th Annual Symposium of the Society for the Study of Inborn Errors of Metabolism in September, 1988 in Glasgow, Scotland.     

Prospective ascertainment of complete and partial serum biotinidase deficiency in the newborn

Summary We screened 163 000 newborn filter-paper blood samples for serum biotinidase deficiency (McKusick 25326) and found 15 probands: three had complete deficiency (incidence 18.4 cases per million live births, 95% confidence interval 4–54 cases per million); the others had partial deficiency. The positive predictive value of the test for either form of biotinidase deficiency was 9.86%. We found seasonal variation in biotinidase activity in filter-paper blood samples. The cost per test was Can.$0.27 (1987 dollar value) and per case of complete deficiency ascertained, $15 500. Family studies indicated that complete serum biotinidase deficiency is a homozygous phenotype and partial deficiency is the heterozygous form. Homozygous cases were treated with biotin and have shown no clinical manifestations (55 patient-months of observation). None of the heterozygotes (n=42, age 3 months – 62 years) has clinical manifestations. The number of heterozygotes found by screening was much less than predicted probably because the screening test detects mainly the samples with very low (outlier) biotinidase activity. The variant allele(s) for biotinidase deficiency was more common in French Canadians than in other ethnic groups in Quebec; there was no evidence of regional clustering or founder effect.This is publication no. 89002 from the McGill University-Montreal Children's Hospital Research Institute.     

Neonatal screening for biotinidase deficiency in Hungary: Clinical, biochemical and molecular studies

From 1989 to 2001, 1,336,145 newborns were screened for biotinidase deficiency in Hungary. Fifty-eight children with the disorder were identified as enzyme-deficient. We have characterized the clinical and biochemical features and mutations of 20 of these children. Eleven children had profound biotinidase deficiency, 7 had partial biotinidase deficiency, and 2 were found to be heterozygous for profound deficiency by mutation analysis. Seventeen different mutations were identified in this population including seven novel mutations. Six of these new mutations are missense, 245C>A, 334G>A, 652G>C, 832C>G, 1253G>C, 1511T>A, and one is a unique allelic double mutation [212T>C;236G>A]. Of five Romanian Gypsies, four were homozygous for the 1595C>T mutation and one was heterozygous for this mutation. Most of the children with profound deficiency have been asymptomatic on therapy; however, four exhibited minimal brain abnormalities, motor delay and abnormal blood chemistries. Compliance with therapy must be questioned in these cases. Of clinical importance, all of the children with partial deficiency exhibited mild symptoms at the time of diagnosis, at several weeks to months of age. These symptoms resolved following biotin therapy. This is in contrast to the experience in the United States, where the children with partial deficiency have been asymptomatic at the time of diagnosis. This finding further indicates that children with partial deficiency should be treated. The incidence of biotinidase deficiency in Hungary is more than twice that observed in a worldwide survey. These results indicate that newborn screening in Hungary is effective and warranted.     

Asymptomatic adults and older siblings with biotinidase deficiency ascertained by family studies of index cases

Summary We report 32 biotinidase-deficient patients detected by family studies in the index cases. The study group consisted of 10 mothers, 4 fathers and 18 siblings. There were 17 individuals (3 mothers, 4 fathers and 10 siblings) with profound biotinidase deficiency (BD) (< 10% of mean normal activity) and 15 (7 mothers and 8 siblings) with partial BD (10–30% of mean normal activity). In the profound BD group, only three siblings were symptomatic. Dermatitis, microcephaly, developmental delay and convulsions were observed. The patients with partial BD did not have any clinical symptoms except one sibling with borderline IQ score. None of the parents was symptomatic. Family investigation of patients with BD is very important for the detection of asymptomatic patients who are at risk of exhibiting symptoms at any age. Careful evaluation of these untreated individuals with BD is important to obtain additional information about the natural history of this disorder and may provide clues to phenotype–genotype relationships and treatment regimes.     

BiotinidaseK m-variants: detection and detailed biochemical investigations

Summary We describe a simple method for the detection of biotinidaseK _m-variants and detailed biochemical investigations in 5 such patient. They were detected among 103 patients with plasma biotinidase activity which ranged from undetectable to 30% of the mean normal value. Two different types of biotinidaseK _m-variants were found. (1) In 3 infants biotinidase had a single 105–430-fold elevatedK _m for biocytin. Biotinidase showed very low activities (0.2–4% of the mean normal value) in the routine colorimetric assay and was not functionalin vivo. Accordingly, these patients presented with classical clinical illness. (2) In two patients biotinidase showed biphasic kinetics indicating the presence of one component with a normalK _m and reducedV _max (1.7% and 12%), and another with 330- and 59-fold elevatedK _m, respectively. In these two patients, biotinidase proved to be at least partially functionalin vivo. However, the first patient developed severe symptoms and biotin deficiency late, at the age of 10–15 years, and the second had marginal biotin deficiency at the age of 2 years but no clinical symptoms. Comparative studies revealed that both patients had more severe biotin deficiency than age-matched patients with similar levels of residual biotinidase activity and a single normalK _m. Therefore, all patients with residual biotinidase activity should be evaluated for the presence of aK _m-mutation, since such patients should be treated with biotin. These can easily be detected by including a second substrate concentration (1.5 mmol/L) in the routine colorimetric biotinidase assay which is performed with 0.15 mmol/L biotin. Increased activity with the higher substrate concentration indicates the presence of aK _m-mutation. Detailed kinetic studies are needed to evaluate the distinct forms ofK _m-variants.     

Diaphorase Activity and Variants in Normal Adults and Newborns

S ummary . Red cell NADH-dependent methaemoglobin reductase (diaphorase) activity was estimated in 126 normal healthy adults and 556 newborns of the three major racial groups in Malaysia. The mean enzyme activity in adults was 3.34 units/mg Hb (SD ± 0.63) and in newborns 1.75 u/mg Hb (SD ± 0.48). The difference between the two means is statistically highly significant. Indians, both adults and infants had the lowest mean enzyme activity. Mean activity in a group of newborns whose birth weights were 2.7 kg or more was significantly higher than in a group with lower birth weights. Sixteen newborns had enzyme activity of less than 1 u/mg Hb. Two of them each had one parent whose enzyme level was also very low. Both parents of three others had normal enzyme activity. The lower limit of normal in newborns seemed to overlap with that found in subjects with hereditary methaemoglobin reductase deficiency. One newborn with an extremely low enzyme level had methaemoglobinaemia, but its genetic nature could not be proved because the parents were not available for study. Examination of 108 adults and 527 newborns for diaphorase electrophoretic variants revealed two different and unusual phenotypes in a few Chinese and Indians. Family studies showed that they are genetically determined.     

Neonatal and maternal thrombocytopenia: incidence and immune background

We performed a prospective study on the incidence of thrombocytopenia (t-penia) and its immunological origin in unselected 26,275 mothers and 24,101 newborns. Platelet antibodies were examined by the platelet immunofluorescence test (PIFT) and the monoclonal antibody immobilisation of platelet antigens assay (MAIPA). T-penia (platelet count < 100 x 10(9)/I) was found in 124 (0.5%) mothers (in 0.04%) severe, <50x 10(9)/l) and in 116 (0.5%) newborns (in 0.15% severe); 90 (72.6%) and 112 (96.6%), respectively, were available for further studies. In both groups non-immune t-penia was diagnosed about 4.5 times more often than the immune t-penia. Among 90 mothers, t-penia was severe in 11.1%, antibodies were detected in 17.8%; both factors were not prognostic for delivering thrombocytopenic newborns. Among 112 babies, 21 were delivered by thrombocytopenic mothers and 91 by mothers with normal platelet count; among newborns with immune t-penia the proportion of alloimmune (NAIT) to autoimmune was equal (10 with NAIT, 10 with autoimmune, 4 of them born by mothers with hidden autoimmune t-penia). In 33% of the neonates t-penia was severe, most often among NAIT. In conclusion, although t-penia in mothers as well as in infants is not frequent and severe, and an immune origin not often found, the search for antibodies, in particular alloantibodies, should be done. Even if the serological results are not helpful at the moment, they can be of importance in subsequent pregnancy and for related pregnant women.     

Right ventricular anatomical and functional parameters in healthy Mexican term newborns

Objective:Right ventricle (RV) function plays an important role during fetal and neonatal transitional circulation. Despite the published echocardiography guidelines in children including neonates, there is scare evidence on RV assessment using echocardiography in Mexican neonates. This study was aimed at assessing RV function and anatomical measures in healthy term newborns and defines normal values in this cohort of patients.Methods:A prospective study involving healthy term newborns in a single center were enrolled in the study to assess RV, all patients were recruited within 24-72 h after birth. The right ventricular assessment was performed as per American Society of Echocardiography’s guidelines.Results:Seventy healthy term newborns with a median gestational age of 38 (38.5 ± 2.7) weeks had RV function assessment and anatomical structures measures with a predefined ten echocardiographic parameters protocol. The mean values for: tricuspid valve diameter was 13 mm ± 1.8, basal diameter of the RV 16.7 mm ± 2, RV length 27.8 mm ± 2.2, mid cavity diameter 14.3 mm ± 1.7, RV-anteroinferior basal diameter 21.5 mm ± 2.5, tricuspid regurgitation gradient 13.3 mmHg ± 5.9, tricuspid annular plane systolic excursion 8.7 mm, right ventricular fractional area change (RVFAC) 4 chamber (%) 40.6 ± 7.5, tricuspid E/A 0.7 ± 0.5, myocardial velocities (cm/s) E´ 8 ± 2.7, A´ 9.6 ± 2.4, S´ 6.9 ± 1.2, myocardial performance index 0.5 ± 0.1, RVFAC 3 chamber (%) 37.8 ± 15.8, and pulmonary acceleration time mean value 58.8 ± 14.9. Flattening of interventricular septum was seen in 13% infants.Conclusions:This study describes echocardiographic parameters for anatomical structures and assessment of RV function in healthy term newborns during transitional circulation. We reported novel anatomical measures of the RV; this information can provide normal reference range values and be referenced while assessing RV function in normal and sick newborns during transitional circulation.Key words: Neonates, Right ventricular function, Normal parameters     

Maternal and Neonatal Urinary Iodine Status and its Effect on Neonatal TSH Levels in a Mildly Iodine-Deficient Area

Objective: Iodine deficiency and excess are the most important factors that affect screening and recall rates of congenital hypothyroidism. The purpose of this study was to investigate the urinary iodine status in newborns and their mothers and its effects on neonatal thyroid-stimulating hormone (TSH) levels in a mildly iodine-deficient area.Methods: A total of 116 newborns and their mothers were included in the study. Urinary iodine levels were measured from healthy mothers and their babies on the 5th day following birth. Neonatal TSH levels were screened, and TSH and free thyroxine (fT4) levels were measured on the15th day in the recall cases. T4 treatment was started in infants with high TSH and low fT4 levels. These measurements were repeated on the 30th day in these newborns.Results: Ninety-nine percent of the mothers included in the study were using iodized salt. The median urinary iodine level in the newborns was 279 µg/L, while it was 84 µg/L in their mothers. The rate of iodine deficiency among the mothers was 56.8%, and the rate of iodine excess was 8.6%. This rate was 10.3% for iodine deficiency and 61.2% for iodine excess in the newborns. The recall rate at the screening was 9.5% (n=11). The urinary iodine levels were above 200 µg/L in three newborns who had transient hyperthyrotropinemia.Conclusions: Iodine deficiency was more frequently observed in nursing mothers, and iodine excess was more frequently seen in their newborns. The iodine excess noted in the newborns was attributed to the use of antiseptics containing iodine. The iodine excess leads to increases in recall rates, screening costs, and frequency of transient hyperthyrotropinemia.Conflict of interest:None declared.     

Pulse oximetry: what's normal in the newborn nursery?

The objective of this study was to establish normal values for pulse oximetry saturation (POS) in healthy newborn infants in the nursery. POS values were obtained from the right (R) hand and R foot at admission, 24 hr, and at discharge. The following information was recorded: postnatal age, activity state, gender, gestational age (GA), birth weight (BW), mode of delivery (MOD), and Apgar scores. Charts were reviewed and follow-up information was obtained for newborns with measurements < or =92%. The study group consisted of a convenience sample of newborn infants, excluding those on supplemental oxygen. Seven hundred eighteen patients were studied: 51% males, 28% cesarean sections, gestational age 39.3+/-1.6 weeks (mean +/- SD), birth weight 3370+/-550 g, and median Apgar scores 8 and 9. The mean POS was 97.2 +/-1.6%, and the median value was 97%. Only postnatal age and activity state affected POS significantly. POS increased 0.17% per 24 hr in the nursery (P = 0. 0001). POS values obtained while the infants were fussy and crying were lower compared to measurements obtained while sleeping [mean decreases: 0.44% while fussy (P = 0.001), 0.98% while crying (P = 0.0001)]. We conclude that newborns in the nursery have an overall mean POS of 97.2% (+/-2 SD: 94-100%). Mean POS values increase to a small degree with increasing postnatal age. Fussy and crying newborns have lower POS values compared to quiet and sleeping newborns. These reference data can be used in the evaluation of POS measurements in symptomatic newborn infants.     

Biotinidase Activity in Patients with Liver Disease

To investigate whether biotinidase deficiency may occur in liver disease, we determined biotinidase activity, biotin levels, and organic acids in patients with liver disease. Serum biotinidase activity in patients with liver disease (2.63 1.40 nmol/min/ml) was significantly lower than in the control group (5.43 1.06 nmol/min/ml). Serum biotinidase activity in decompensated liver cirrhosis (LC) and hepatoma was significantly lower than in acute viral hepatitis (AVH), chronic viral hepatitis (CVH), and compensated LC. The mean serum level of biotin in decompensated LC (1.8 0.6 μg/ml) and hepatoma (1.7 0.8μg/ml) was significantly lower than in the control group (2.5 1.0 μg/ml), and urinary excretion of biotin was increased in patients with liver disease, particularly in decompensated LC. Biotinidase activity correlated positively with serum biotin level and correlated negatively with urinary biotin level. Moreover, in four of five patients with severe liver disease the excretion of propionate, lactate, and 3-hydroxybutyrate decreased after biotin supplementation. The data for patients with severe liver disease so resembled those for late-onset multiple carboxylase deficiency that biotinidase deficiency is likely in patients with severe liver disease.     

Long-term outcome of expanded newborn screening at Boston children’s hospital: benefits and challenges in defining true disease

Introduction

There is no universal consensus of the disorders included in newborn screening programs. Few studies so far, mostly short-term, have compared the outcome of disorders detected by expanded newborn screening (ENBS) to the outcome of the same disorders detected clinically.

Methods

We compared the clinical and neurodevelopmental outcomes in patients with metabolic disorders detected by ENBS, including biotinidase testing, with those detected clinically and followed at the Metabolism Clinic at Boston Children’s Hospital.

Results

One hundred eighty-nine patients came to attention from ENBS and 142 were clinically diagnosed. 3-methylcrotonyl-CoA carboxylase, biotinidase, and carnitine deficiencies were exclusively identified by ENBS and medium chain acyl-CoA dehydrogenase (MCADD) and very long chain acyl-CoA dehydrogenase deficiencies (VLCADD) were predominantly identified by ENBS whereas the organic acid disorders more often came to attention clinically. Only 2% of the ENBS-detected cases had clinically severe outcomes compared to 42% of those clinically detected. The mean IQ score was 103?+?17 for the ENBS-detected cases and 77?+?24 for those clinically detected. Those newly included disorders that seem to derive the greatest benefit from ENBS include the fatty acid oxidation disorders, profound biotinidase deficiency, tyrosinemia type 1, and perhaps carnitine deficiency.

Conclusion

Although the NBS-identified and clinically-identified cohorts were not completely comparable, this long-term study shows likely substantial improvement overall in the outcome of these metabolic disorders in the NBS infants. Infants with mild disorders and benign variants may represent a significant number of infants identified by ENBS. The future challenge will be to unequivocally differentiate the disorders most benefitting from ENBS and adjust programs accordingly.

     

Epidemiology of Congenital Hypothyroidism in Markazi Province,Iran

Ob­jec­ti­ve: The aim of this study was to investigate the epidemiology of congenital hypothyroidism (CH) among newborns in Markazi Province, Iran.Methods: This cross-sectional study was conducted from 2006 to 2012. Blood samples were taken between 3 to 5 days after birth from the heel. Thyroid stimulating hormone (TSH) was tested using the enzyme-linked immunosorbent assay method and was employed as the screening test. Newborns with abnormal screening results (TSH >5 mIU/L) were re-examined. The data were analyzed using SPSS.Results: A total of 127 112 infants were screened. Of these, 51.2% were male and 48.8% were female. The coverage rate of the screening program was 100%. Of 6102 recalled subjects (re-call rate 4.8%), 414 cases with CH were detected, yielding a CH prevalence of 1:307 (female:male ratio 1:0.95). The prevalence of permanent and transient CH was 1:581 and 1:628, respectively.Conclusion: This study reveals that the prevalence of CH is higher compared to worldwide levels. Comprehensive and complementary studies for recognizing related risk factors should be a priority for health system research in this province.     

Craniotabes in normal newborns: the earliest sign of subclinical vitamin D deficiency

CONTEXT: Craniotabes in otherwise normal neonates has been regarded as physiological and left untreated. OBJECTIVE: Our objective was to investigate the role of vitamin D deficiency in the development of craniotabes in normal neonates. DESIGN AND SETTING: Newborn screening of craniotabes was conducted at the single largest obstetrical facility in Kyoto, Japan. Follow-up study at 1 month was conducted at Kyoto University Hospital. SUBJECTS: A total of 1120 consecutive normal Japanese neonates born in May, 2006, through April, 2007, were included in the study. MAIN OUTCOME MEASURES: The incidence of craniotabes was scored each month. Neonates with craniotabes were followed up at 1 month with measurements of serum calcium, phosphorus, alkaline phosphatase (ALP), intact PTH, 25-OH vitamin D (25-OHD), urinary calcium, phosphorus, creatinine, and hand x-rays. RESULTS: Craniotabes was present in 246 (22.0%) neonates, and the incidence had obvious seasonal variations, highest in April-May and lowest in November. At 1 month, infants with craniotabes had significantly higher serum ALP compared with normal neonates; 6.9% of them had elevated intact PTH over 60 pg/ml, and 37.3% had 25-OHD less than 10 ng/ml. When separately analyzed according to the method of feeding, 56.9% of breast-fed infants showed 25-OHD less than 10 ng/ml, whereas none of formula/mixed-fed infants did, and breast-fed infants had significantly higher serum PTH and ALP compared with formula/mixed-fed infants. SUMMARY: These results suggest that craniotabes in normal neonates is associated with vitamin D deficiency in utero, and the deficiency persists at 1 month in many of them, especially when breast-fed.     

Urinary iodide levels in term newborns and their mothers--a pilot study

Although the Philippines is considered an iodine-deficient country, there are no documented iodine deficiency disorders (IDD) among newborns screened to be positive for congenital hypothyroidism. The objectives of this pilot study were: (1) to determine the levels of urinary iodide (UI) in normal term newborns and their mothers, and (2) to correlate the UI levels of newborns with that of their mothers. This study included 44 pairs of full term newborns and their mothers who delivered at two hospitals in Manila last July 2001. UI determination by the Rapid Urinary Iodide Test was done during the first 24 hours after delivery. Results showed that eighteen percent (8/44) of the neonates were iodine deficient (<10 microg/dl), 71% (31/44) had adequate UI levels (>10-30microg/dl) and 11% (5/44) had high UI levels (>30microg/dl). None of the mothers had deficient UI levels. Among the neonates who had deficient UI levels, 50% (4/8) of the mothers had adequate UI levels and the other half (4/8) had high levels. Among the neonates who had adequate UI levels, most mothers had high UI levels (22/31 or 71%) and the rest (9/31 or 29%) had adequate UI. All newborns with high UI levels had mothers with high UI levels. Screening for Congenital Hypothyroidism was negative in all the neonates who underwent newborn screening (39/44). In conclusion, most term neonates (82%) had adequate to high UI levels, and 18% had deficient UI levels despite adequate maternal levels. In case of low UI level, repeat determination is advised. If the level remains low, newborn screening using TSH is useful to rule out hypothyroidism. A bigger multicenter study to determine the incidence of IDD in neonates and infants is recommended.     

Specific impairment of cell-mediated immunity in mothers of infants with congenital infection due to cytomegalovirus.

Specific lymphocyte-mediated cytotoxicity to cytomegalovirus (CMV) in eight infants (six to 27 months old) with congenital CMV infection and in the mothers of six of these infants was evaluated with use of a 51chromium (51Cr)-release microassay. The control population consisted of 25 normal newborns, children, and adults. The titers of indirect hemagglutinating (IHA) antibody to CMV in the infected infants ranged from 1:16 to 1:1,024. All of these infants had detectable specific immune release of 51Cr that ranged from 3.3% to 48.9% (mean +/-SE, 21.0%+/-5.6%). The mothers of these infants demonstrated significantly elevated titers of IHA antibody to CMV (geometric mean titer, 1:410) as compared with a mean titer of 1:22 in controls (t = 5.71; P less than 0.001) but showed significantly depressed specific immune release (9.2% +/- 3.2%) compared with that of normal seropositive controls (24.8% +/- 2.8%; t = 3.31; P less than 0.001). In addition, two adult nulliparous women with persistent CMV viruria were also found to have depressed specific immune release to CMV (10.8% and 16.2%). These data suggest that a specific impairment in cell-mediated immunity to CMV occurs in mothers of infants with congenital CMV infection and in some persons who persistently excrete CMV.     

Neonatal screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in The Netherlands: The importance of enzyme analysis to ascertain true MCAD deficiency

Summary The outcome was determined of population-wide neonatal screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency using tandem mass spectrometry (MS/MS) in The Netherlands, between October 2003 and September 2005. Prospective population-wide neonatal screening for MCAD deficiency was performed in the northern part of The Netherlands. In newborns with blood octanoylcarnitine (C_8:0) concentrations ≥0.3 μmol/L, clinical and laboratory follow-up was initiated, including MCAD enzymatic measurements which played a decisive role. In a 2-year period, 66 216 newborns were investigated for MCAD deficiency and follow-up was initiated in 28 newborns. True-positives (n = 14) were identified based upon MCAD enzyme activity <50%, measured with hexanoyl-CoA as substrate. The observed prevalence of MCAD deficiency was 1/6600 (95% CI: 1/4100–1/17 400). In addition to an elevated C_8:0 concentration, a C_8:0/C_10:0 molar ratio >5.0 turned out to differentiate between false-positives and true-positives. Measurement of MCAD activity using phenylpropionyl-CoA as a substrate further discriminated between newborns with MCAD deficiency and so-called mild MCAD deficiency. To summarize, neonatal screening for MCAD deficiency in the northern part of The Netherlands resulted in the predicted number of affected newborns. Measurement of MCAD activity in leukocytes or lymphocytes using phenylpropionyl-CoA as a substrate can be regarded as the gold standard to diagnose MCAD deficiency upon initial positive screening test results. Competing interests: None declared     

Evaluation of 3-methylcrotonyl-CoA carboxylase deficiency detected by tandem mass spectrometry newborn screening

Summary: Since the addition of tandem mass spectrometry (MS/MS) to the North Carolina Newborn Screening Program, 20 infants with two consecutive elevated 3-hydroxyisovalerylcarnitine (C₅OH) levels have been evaluated for evidence of inborn errors of metabolism associated with this metabolite. Ten of these 20 infants had significant concentrations of both 3-hydroxyisovaleric acid and 3-methylcrotonylglycine in their urine, suggestive of 3-methylcrotonyl-CoA carboxylase (3-MCC) deficiency. Four of these 10 were infants whose abnormal metabolites were found to be of maternal origin. Of 8 patients with probable 3-MCC deficiency, 7 have been tested and found to have the enzyme deficiency confirmed in lymphoblasts or cultured fibroblasts; one of these 7 infants had only marginally decreased 3-MCC activity in lymphocytes but deficient 3-MCC in fibroblasts. We estimate the incidence of 3-MCC deficiency at 1:64000 live births in North Carolina. We conclude that MS/MS newborn screening will detect additional inborn errors of metabolism, such as 3-MCC deficiency, not traditionally associated with newborn screening. The evaluation of newborns with two abnormally elevated C₅OH levels on MS/MS newborn screening should include, at least, urine organic acid analysis by capillary GC-MS and a plasma acylcarnitine profile by MS/MS. Long-term follow-up is needed to determine the outcome of presymptomatically diagnosed patients with 3-MCC deficiency by MS/MS newborn screening.     

Two new mutations in children affected by partial biotinidase deficiency ascertained by newborn screening

Mutation analysis performed on DNA from 6 Italian patients with partial biotinidase deficiency ascertained by newborn screening allowed the identification of two new mutations, c1211C>T (T404I) and a single base deletion c594delC. All patients were compound heterozygous for the D444H amino acid substitution showing that this mutation is also common in Italian patients affected by partial biotinidase deficiency.