Neonatal Screening For Biotinidase Deficiency Research Articles

Neuroimaging Features of Biotinidase Deficiency.

Biotinidase deficiency is an autosomal recessive condition caused by pathogenic variants in the BTD gene. Resultant deficiency of free biotin leads to impaired activity of the enzyme carboxylase and related neurologic, dermatologic, and ocular symptoms. Many of these are reversible on treatment, but early recognition and commencement of biotin supplementation are critical. This practice is especially important in countries where routine neonatal screening for biotinidase deficiency is not performed. In this report comprising 14 patients from multiple centers, we demonstrate the MR imaging patterns of this disorder at various age groups. Knowledge of these patterns in the appropriate clinical context will help guide early diagnosis of this treatable metabolic disorder.

Diagnosis and management of symptomatic profound biotinidase deficiency in a tertiary care center in Lebanon

Neonatal screening for biotinidase deficiency is still lacking in several countries worldwide, although this neurocutaneous disorder is treatable and preventable. Therefore, unscreened patients are diagnosed when symptomatic; treatment with Biotin is known to reverse cutaneous symptoms and improve neurological outcome. We describe a series of five symptomatic patients diagnosed with profound biotinidase deficiency and followed at a tertiary care center in Lebanon, for a variable period from 16 months to 11 years. Adjustment of Biotin therapy is correlated to clinical response and biochemical profile including 3-hydroxyisovalerylcarnitine on dried blood spots and urine organic acids. A previously unreported mutation is also reported in a patient who displayed an unusual outcome with reversible hearing loss on Biotin therapy.Clinical responsiveness to Biotin may be related to the underlying genetic mutation, although no clear genotype-phenotype correlation in biotinidase deficiency is proven. Furthermore, in the absence of systematic newborn screening for this disorder in several countries, identification of a reliable blood biomarker of Biotin responsiveness is warranted for better management of late diagnosed symptomatic patients.

Neonatal screening for biotinidase deficiency: A 30-year single center experience

We reviewed the outcome of newborn screening for biotinidase deficiency performed at our department since 1987. Among 1,097,894 newborns screened, 461 were recalled, and 18 were identified as affected by complete or partial biotinidase deficiency (incidence 1:61,000, false positive rate 0.04%). The common missense mutation Q456H was found in 80% of patients with profound biotinidase deficiency. Of them, one patient harbored the novel mutation M399I in compound heterozygosity (M399I/Q456H). The complex allele A171T/D444H in cis was found in two patients with profound biotinidase deficiency (in homozygosity and in compound heterozygosity with the R211H mutation, respectively) and in one patient with partial biotinidase deficiency (in compound heterozygosity with the protective allele D444H in trans).All detected patients were treated and followed up at our Center until present. Biotin therapy (10–20mg/day) allowed the full prevention of clinical symptoms in all patients with no adverse effects. These excellent outcomes confirm that newborn screening for biotinidase deficiency is a very effective secondary prevention program.

The importance of a law on time: presentation of a girl with biotinidase deficiency who was not picked up through the neonatal screening

In August 2008, the province of Buenos Aires had not adhered to the National law number 26279, that establishes the obligatory nature of the neonatal screening for biotinidase deficiency, among other diseases. In that date, a girl was born in Buenos Aires. She was admitted in the Hospital "J. P. Garrahan" with lethargy, metabolic acidosis, hiperlactacidemia, alopecia, conjuntivitis and scaly erythematous eruption in trunk, at 58 days of life, from a pediatric intensive care unit. Due to this clinic (13 days of evolution), a biotinidase assay in serum was done. This was abnormally low. She initiates treatment with biotin and the biochemical abnormalities revert quickly. If the neonatal screening had been done, this girl wouldn't have been exposed at risk of death, and a normal development would have been assure (by the presymptomatic beginning of the treatment), since the neurological injuries not always go back ad integrum.

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.

Statistical approaches for the detection of heterozygotes for biotinidase deficiency

We applied and evaluated 3 statistical approaches for the detection of heterozygotes for biotinidase deficiency in a randomly selected population of French adults. The first method, which used a cutoff value to dichotomize the population, lacked sensitivity. The second approach calculated the probability of heterozygosity for a given enzyme activity through the application of Bayes theorem to the normal density functions of the enzyme distributions of the obligate heterozygote and the test populations. A priori values of the means and standard deviations (SDs) of the genotypic distributions were used. This method was sufficiently sensitive for both population screening and genetic counseling, but requires prior knowledge of the frequency of the deficient gene (q). The third approach was similar to the second, however, maximum likelihood estimates of the means and SDs of the genotypic distributions were calculated and used to determine the probability of heterozygosity for a given enzyme activity. This method was as sensitive as the second method and is appropriate for screening populations for which there is little prior information about the gene frequency and the genotypic distributions. This method can also be used to estimate the gene frequency of the disorder within a given ethnic or racial population. Using this method, we estimated the frequency of heterozygotes (2pq) in the French population to be 0.012, which was similar to that estimated from the results of neonatal screening for biotinidase deficiency. These methods can be used to detect heterozygotes and to estimate the gene frequency of other inherited enzyme deficiencies.

Worldwide survey of neonatal screening for biotinidase deficiency

Neonatal screening for biotinidase deficiency has been conducted in 14 countries since 1984. To 31 December 1990, 8,532,617 newborns were screened. One hundred and forty-two infants with biotinidase deficiency were identified; 76 infants with profound deficiency (less than 10% of mean normal serum activity) and 66 infants with partial deficiency (10-30% of mean normal activity). The estimated incidence of profound biotinidase deficiency is 1:112,271 (1:85,000 to 1:145,000; 95% confidence limits) and the incidence of partial deficiency is 1:129,282 (1:112,700 to 1:177,000). The incidence of combined profound and partial deficiency is 1:60,089 newborns (1:49,500 to 1:73,100). The estimated frequency of the allele for biotinidase deficiency is 0.004 and an estimated 1 in 123 individuals is heterozygous for the disorder.

Neonatal screening for biotinidase deficiency in East‐Hungary

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.

Neonatal screening for biotinidase deficiency. A pilot study in scotland

The method of Heard et al. (1984) was used to screen 102393 Guthrie card dried blood spots (3 mm) in a study to determine the prevalence of biotinidase (EC 3.5.1.12) deficiency in the Scottish neonatal population during the period December 1985 to July 1987

Neonatal screening for biotinidase deficiency in north eastern Italy.

Biotinidase deficiency satisfies all the criteria for incorporation into neonatal mass screening programmes for inborn errors of metabolism. We report our preliminary experiences with screening of 24,300 newborns during a 6 month-period when 1 infant with biotinidase deficiency was detected. On the basis of these results, this disorder appears to be as common as other well known metabolic disorders for which mass screening is available.

Neonatal screening for biotinidase deficiency: Results of a 1-year pilot study

We screened 81,243 infants born in Virginia during the 1-year period beginning Jan. 24, 1984, for deficiency of the enzyme biotinidase. A simple colorimetric screening procedure was used to detect the presence or absence of biotinidase activity on the same blood-soaked filter paper cards that are currently used in most neonatal metabolic screening programs. Two newborn infants with biotinidase deficiency were identified during the 12-month pilot study. In addition, two affected siblings of one of the newborn infants were detected through secondary family screening. On the basis of these results, the disorder appears to be at least as frequent as several others for which newborn screening is currently conducted. There were no known false-negative test results, and only 0.09% false-positive results that necessitated requests for second blood samples. False-positive test results can be readily identified by the use of a quantitative assay, which can also be used to confirm the diagnosis and to detect heterozygous family members in the case of true positives. On the basis of currently recognized criteria, biotinidase deficiency should be considered for inclusion among the metabolic disorders for which screening is performed in the neonatal period.