Multiple carboxylase deficiency (MCD) includes autosomal recessive holocarboxylase synthetase (HLCS) deficiency and biotinidase (BTD) deficiency, which are caused by and gene mutations respectively. Neonatal screening for HLCS deficiency is based on 3-hydroxyisovaleryl carnitine in dry blood filter paper, and BTD deficiency is based on BTD activity determination. HLCS deficiency and BTD deficiency are characterized by neurocutaneous syndrome and organic aciduria, however, they are different in onset age, neurological symptoms and metabolic decompensation, which needed to be differentiated from acquired biotin deficiency or other genetic metabolic diseases. The diagnosis of the disease requires a combination of biochemical characteristics of hematuria, enzyme activity determination and genetic test. Routine biotin doses are effective for most MCD patients. This consensus is intended to benefit early screening and diagnosis of MCD.
Biotin/therapeutic use* ; Biotinidase Deficiency/therapy* ; Carbon-Nitrogen Ligases/metabolism* ; Consensus ; Holocarboxylase Synthetase Deficiency/genetics* ; Humans ; Infant, Newborn ; Multiple Carboxylase Deficiency/drug therapy* ; Neonatal Screening

OBJECTIVEMultiple carboxylase deficiency (MCD) is an autosomal recessive disorder. MCD is characterized by skin rash, metabolic acidosis, vomiting and psychomotor retardation. Depending on deficiency of the enzyme, MCD includes two different forms, biotinidase deficiency (BTD, OMIM 253260) and holocarboxylase synthetase deficiency (HLCSD, OMIM 253270). In this study, we analyzed gene mutations of four Chinese MCD patients and to explore the mutation spectrum and possibility of a molecular diagnosis.

METHODSAll exons and their flanking introns of biotinidase gene and HLCS gene were screened by polymerase chain reaction combined with DNA direct sequencing in four Chinese MCD patients. Genomic DNA was extracted using a kit from the peripheral blood leukocytes of each patient. PCR amplification products were checked by 2% agarose gel electrophoresis and were subsequently sequenced with both the forward and reverse primers.

RESULTSAll patients showed mutations in HLCS gene, whereas no mutation was found in biotinidase gene, proving that all the four patients had HLCS deficiency. Four previously reported mutations in HLCS gene were detected (Y456C, R508W, D634N and 780delG). A missense mutation of 1522C > T in exon 11 of HLCS gene, which was a homozygotic mutation, was identified in patient 1; a mutation of 1522C > T in exon 11 combined with a mutation of 1367A > G in exon 9, which was a compound heterozygotic mutation, was identified in patient 2; a mutation of 1522C > T in exon 11 combined with a mutation of 1900G > A in exon 13, which was a compound heterozygotic mutation, was identified in patient 3; a mutation of 1522C > T in exon 11 combined with a mutation of 780delG in exon 7, which was a compound heterozygotic mutation, was identified in patient 4. All the parents were carriers of mutations. No additional carrier of this four mutations was identified from 50 samples of Chinese controls.

CONCLUSIONThe 1522C > T (R508W) mutation probably represents a mutational hot-spot in Chinese HLCS deficiency patients while the 780delG mutation which was reported only in Japanese patients was found firstly in Chinese patients.

Asian Continental Ancestry Group ; genetics ; Biotinidase ; genetics ; Carbon-Nitrogen Ligases ; genetics ; DNA Mutational Analysis ; Exons ; Female ; Holocarboxylase Synthetase Deficiency ; enzymology ; genetics ; Humans ; Infant ; Infant, Newborn ; Introns ; Male

OBJECTIVETo report the clinical diagnosis, treatment and follow-up of children with holocarboxylase synthetas(HCS) deficiency and explore the gene mutation spectrum of the disease.

METHODSEleven children with HCS deficiency were enrolled. Mass spectrometry analysis and biotinidase activity determination were used for diagnosis of HCS deficiency. HCS gene mutations were analyzed by PCR directed sequencing methods. Ten patients received oral biotin treatment (10-40 mg/d). Clinical effects of biotin treatment were observed.

RESULTSAll 11 cases developed apathetic, lethargy and metabolic acidosis at different degrees, and 10 cases presented with skin lesions. The average blood 3-hydroxyisovaleryl-carnitine concentrations and urinary 3-methylcrontonylglycine and methylcitrate concentrations increased significantly. The biotinidase activity increased, being higher over 30% of the normal reference value. Four mutations in HCS gene were identified, and they were c.1522C>T (R508W), c.1088T>A (V363D), c.126G>T (E42D) and c.1994G>C (R665P) (a new variant) and the frequency was 50%, 29%, 7% and 14% respectively. The symptoms disappeared in 10 cases 1-2 weeks after biotin treatment, and blood and urinary abnormal metabolites were gradually reduced to normal 2-6 months after treatment.

CONCLUSIONSHCS deficiency is characterized by nervous system damage, skin lesions and metabolic acidosis. Mass spectrometry analysis, biotinidase activity determination and gene mutation analysis may be helpful in the definite diagnosis of this disorder. The effect of early biotin treatment is satisfactory. The mutations R508W and V363D might be hot-spots in Chinese children with HCS deficiency.

Biotin ; therapeutic use ; Biotinidase ; metabolism ; Carbon-Nitrogen Ligases ; genetics ; Child, Preschool ; Female ; Holocarboxylase Synthetase Deficiency ; diagnosis ; therapy ; Humans ; Infant ; Infant, Newborn ; Male ; Mutation