[Screening indices and their cut-off values for full-term neonates carrying ß-thalassemia gene].

OBJECTIVE: To investigate the screening indices and their cut-off values for full-term neonates carrying ß-thalassemia gene. METHODS: A retrospective analysis was performed for the clinical data of 1 193 full-term neonates who underwent ß-thalassemia screening (hemoglobin analysis with dried blood spots on neonatal heel blood filter paper and mutation detection of 17 ß-globin genes). A multivariate logistic regression analysis was used to investigate the association between screening indices and ß-thalassemia gene, and the receiver operating characteristic (ROC) curve was used to analyze the value of screening indices in determining the presence or absence of ß-thalassemia gene. RESULTS: Of the 1 193 neonates, 638 carried ß-thalassemia gene. Of the 1 193 neonates, 637 (53.39%) had no HbA2, among whom 310 carried ß-thalassemia gene and 327 did not carry this gene; 556 (46.61%) had HbA2, among whom 328 carried ß-thalassemia gene and 228 did not carry this gene. As for the neonates without HbA2, the ß-thalassemia gene group had a significantly lower HbA level and a significantly higher HbF level than the ß-thalassemia gene-negative group (P<0.01). As for the neonates with HbA2, the ß-thalassemia gene group had a significantly lower HbA level and significantly higher HbF and HbA2/HbA ratio than the ß-thalassemia gene-negative group (P<0.01). In the neonates without HbA2, HbA, gestational age, and HbA combined with gestational age had an area under the ROC curve (AUC) of 0.865, 0.515, and 0.870, respectively, in determining the presence or absence of ß-thalassemia gene (P<0.01), and HbA and HbA combined with gestational age had a similar AUC and a certain diagnostic value. In the neonates with HbA2, HbA, HbA2/HbA ratio, and HbA combined with HbA2/HbA ratio had an AUC of 0.943, 0.885, and 0.978, respectively, in determining the presence or absence of ß-thalassemia gene. The HbA combined with HbA2/HbA ratio had the largest AUC. In the neonates without HbA2, HbA had the largest AUC in determining the presence or absence of ß-thalassemia gene at the cut-off value of 11.6%, with a sensitivity of 85.81% and a specificity of 79.82%. In the neonates with HbA2, an HbA of 16.1%-22.0% and an HbA2/HbA ratio of >1.4 had the largest AUC in determining the presence or absence of ß-thalassemia gene, with a sensitivity of 91.38% and a specificity of 91.89%. CONCLUSIONS: HbA and HbA2/HbA ratio are effective indices for screening out full-term neonates carrying ß-thalassemia gene.

[Genetic diagnosis of 10 neonates with primary carnitine deficiency].

OBJECTIVE: To study the gene mutation profile of primary carnitine deficiency (PCD) in neonates, and to provide a theoretical basis for early diagnosis and treatment, genetic counseling, and prenatal diagnosis of PCD. METHODS: Acylcarnitine profile analysis was performed by tandem mass spectrometry using 34 167 dry blood spots on filter paper. The SLC22A5 gene was sequenced and analyzed in neonates with free carnitine (C0) levels lower than 10 µmol/L as well as their parents. RESULTS: In the acylcarnitine profile analysis, a C0 level lower than 10 µmol/L was found in 10 neonates, but C0 level was not reduced in their mothers. The 10 neonates had 10 types of mutations at 20 different sites in the SLC22A5 gene, which included 4 previously unreported mutations: c.976C>T, c.919delG, c.517delC, and c.338G>A. Bioinformatics analysis showed that the four new mutations were associated with a risk of high pathogenicity. CONCLUSIONS: Tandem mass spectrometry combined with SLC22A5 gene sequencing may be useful for the early diagnosis of PCD. Identification of new mutations enriches the SLC22A5 gene mutation profile.

[An analysis of clinical characteristics and gene mutation in two patients with medium- and short-chain acyl-CoA dehydrogenase deficiency].

Medium- and short-chain acyl-CoA dehydrogenase deficiency is a disorder of fatty acid ß-oxidation. Gene mutation prevents medium- and short-chain fatty acids from entry into mitochondria for oxidation, which leads to multiple organ dysfunction. In this study, serum acylcarnitines and the organic acid profile in urea were analyzed in two children whose clinical symptoms were hypoglycemia and metabolic acidosis. Moreover, gene mutations in the two children and their parents were evaluated. One of the patients was a 3-day-old male who was admitted to the hospital due to neonatal asphyxia, sucking weakness, and sleepiness. The serum acylcarnitine profile showed increases in medium-chain acylcarnitines (C6-C10), particularly in C8, which showed a concentration of 3.52 µmol/L (reference value: 0.02-0.2 µmol/L). The analysis of organic acids in urea gave a normal result. Sanger sequencing revealed a reported c.580A>G (p.Asn194Asp) homozygous mutation at exon 7 of the ACADM gene. The other patient was a 3-month-old female who was admitted to the hospital due to cough and recurrent fever for around 10 days. The serum acylcarnitine profile showed an increase in serum C4 level, which was 1.66 µmol/L (reference value: 0.06-0.6 µmol/L). The analysis of organic acids in urea showed an increase in the level of ethyl malonic acid, which was 55.9 (reference value: 0-6.2). Sanger sequencing revealed a reported c.625G>A (p.Gly209Ser) homozygous mutation in the ACADS gene. This study indicates that screening tests for genetic metabolic diseases are recommended for children who have unexplained metabolic acidosis and hypoglycemia. Genetic analyses of the ACADM and ACADS genes are helpful for the diagnosis of medium- and short-chain acyl-CoA dehydrogenase deficiency.

[CPT2 gene mutation analysis and prenatal diagnosis in a family with carnitine palmitoyltransferase II deficiency].

This study aimed to identify the type of carnitine palmitoyltransferase 2 (CPT2) gene mutation in the child with carnitine palmitoyltransferase II (CPT II) deficiency and her parents and to provide the genetic counseling and prenatal diagnosis for the family members. As the proband, a 3-month-old female baby was admitted to the hospital due to fever which had lasted for 8 hours. Tandem mass spectrometric analysis for blood showed an elevated plasma level of acylcarnitine, which suggested CPT II deficiency. The genomic DNA was extracted from peripheral blood of the patient and her parents. Five exon coding regions and some intron regions at the exon/intron boundaries of the CPT2 gene were analyzed by PCR and Sanger sequencing. Amniotic fluid was taken from the mother during the second trimester, and DNA was extracted to analyze the type of CPT2 gene mutation. Sanger sequencing results showed that two mutations were identified in the CPT2 gene of the proband: c.886C>T (p.R296X) and c.1148T>A (p.F383Y), which were inherited from the parents; the second child of the mother inherited the mutation of c.886C>T (p.R296X) and showed normal acylcarnitine spectrum and normal development after birth. It is concluded that the analysis of CPT2 gene mutations in the family suggested that the proband died of CPT II deficiency and that the identification of the mutations was helpful in prenatal diagnosis in the second pregnancy.

[Pancytopenia and metabolic decompensation in a neonate].

A 9-day-old male patient was admitted to the hospital because of cough, anhelation, feeding difficulty and lethargy. The diagnostic examinations indicated pulmonary infection, severe metabolic acidosis, hyperglycemia, hyperammonemia and pancytopenia in the patient. Blood and urine screening and isovaleryl-CoA dehydrogenase (IVD) gene detection for inherited metabolic diseases were performed to clarify the etiology. Tandem mass spectrometric screening for blood showed an elevated isovalerylcarnitine (C5) level. The organic acid analysis of urine by gas chromatography-mass spectrometry showed significantly increased levels in isovaleryl glycine and 3-hydroxyisovaleric acid. Homozygous mutations (c.1208A>G, p.Tyr403Cys) in the IVD gene were identified in the patient. His parents were heterozygous carriers. After the treatment with low-leucine diets and L-carnitine for 3 days, the patient showed a significant improvement in symptoms, but he died one week later. It is concluded that the neonates with pneumonia and metabolic decompensation of unknown etiology should be screened for genetic metabolic disease.