Expert consensus on screening, diagnosis and treatment of multiple carboxylase deficiency.

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 deficiency in amino acid formula nutrition for an infant with milk protein allergy].

We reported a 4-month-old girl with biotin deficiency caused by amino acid formula. Two weeks after birth, she was diagnosed as having a milk protein allergy. After switching to amino acid formula from usual formula, her symptoms and laboratory findings became normal. About three weeks after the beginning of amino acid formula, she developed intractable skin erosions around the eyes, mouth, neck, and anogenital area. By measuring concentrations of some trace elements, she was diagnosed as having a biotin deficit, because of the organic aciduria and undetectable serum biotin concentration. Her serum biotinidase level was normal. Upon administration of oral biotin supplementation, all her symptoms and laboratory findings were dramatically improved. Since amino acid formula contains very few biotin, we should pay attention to biotin deficiency when infants receiving amino acid formula.

Dermatologic signs of biotin deficiency leading to the diagnosis of multiple carboxylase deficiency.

The biotin-responsive, multiple carboxylase deficiencies are autosomal recessively inherited disorders of metabolism in which biotin-dependent carboxylases show diminished activity. This results in an accumulation of organic acids in the urine. The clinical picture involves the nervous system, skin, respiratory system, digestive system, and immune system. The disorder has a good prognosis if biotin therapy is introduced early. If not, it can result in irreversible damage to the central nervous system and early death from metabolic acidosis. We report a 4-year-old girl with unexplained seizures that did not respond well to anticonvulsants. The development of skin problems, which histologically could match the diagnosis of a nutritional dermatitis, together with the fact that the child was constantly eating without gaining weight, led us to the diagnosis of a metabolic disorder. The accumulation of organic acids in the urine suggested the possibility of a biotin deficiency. With biotin therapy the skin problems resolved completely. The seizures also diminished. This case shows that in young children with unexplained seizures that do not respond well to classic anticonvulsant therapy, the possibility of biotin deficiency should always be considered. This article also includes a thorough review of the skin manifestations and other problems caused by biotin deficiency.

Biotin responsive multiple carboxylase deficiency presenting as diabetic ketoacidosis.

Multiple carboxylase deficiency (MCD) is a rare inherited metabolic disease of biotin dependency due to deficiency of holocarboxylase synthetase (HCS) or biotinidase deficiency. A 30-month-old female patient who presented with the initial features of diabetic ketoacidosis (severe metabolic acidosis, ketosis, and hyperglycemia), lactic acidemia, moderate hyperammonemia, and generalized organic aciduria is described. Associated symptoms and signs included erythematous skin rashes, alopecia and developmental delay. The patient responded dramatically to treatment with biotin (10 mg/day) showing normalization of clinical symptoms and most biochemical abnormalities. Based on the urine organic profile by gas chromatography/ mass spectrometry (GC/MS), the diagnosis of MCD was made. A plasma tandem mass study confirmed this diagnosis. The biotinase activity in serum was normal, indicating that this was a rare case of late-onset HCS deficiency.

Prenatal diagnosis and treatment of holocarboxylase synthetase deficiency.

Holocarboxylase synthetase is one of two enzymes known to be involved in the metabolism of biotin. It catalyses the fixation of biotin to inactive apocarboxylases yielding active carboxylases. Deficiency of this enzyme leads to multiple carboxylase deficiency which is fatal in the absence of prompt diagnosis and treatment with biotin. In a pregnancy at risk for deficiency of holocarboxylase synthetase prenatal diagnosis was performed by assay of the enzyme in amniocytes. The Km for biotin was 62.8 nM which was 12 times the control value of 5.0 nM. The Vmax was 2 per cent of the control value. This was confirmed by assay of the activity of propionyl CoA carboxylase (20-26 per cent control), 3-methylcrotonyl CoA carboxylase (14-19 per cent control) and pyruvate carboxylase (12-30 per cent control) and demonstration of biotin responsiveness in vitro. All carboxylase activities were restored to 51-58 per cent of control when amniocytes were cultured in medium containing 1 microM biotin. Diagnosis was ultimately confirmed by assay of holocarboxylase synthetase in lymphocytes from the infant after birth. The Km for biotin of the holocarboxylase synthetase of the infant was 60.3 nM while that of a parallel control was 6.9 nM. Prenatal treatment of the mother with biotin led to a concentration of biotin of 240 nM in the serum of the infant at birth that was four times the Km of the enzyme for biotin. The infant was clinically well at birth, and organic acid analysis of the blood and urine revealed no accumulation of the characteristic metabolites.

Bioavailability of biotin given orally to humans in pharmacologic doses.

BACKGROUND: Patients with carboxylase deficiency are treated with pharmacologic doses of biotin. OBJECTIVE: We sought to determine the bioavailability of biotin at pharmacologic doses. DESIGN: Biotin was administered orally (2.1, 8.2, or 81.9 micromol) or intravenously (18.4 micromol) to 6 healthy adults in a crossover design with > or =2 wk between each biotin administration. Before and after each administration, timed 24-h urine samples were collected. Urinary biotin and biotin metabolites were analyzed by an HPLC avidin-binding assay. RESULTS: Urinary recoveries of biotin plus metabolites were similar (approximately 50%) after the 2 largest oral doses and the 1 intravenous dose, suggesting 100% bioavailability of the 2 largest oral doses. For unexplained reasons, the apparent recovery of the smallest oral dose was about twice that of the other doses. For all 4 doses, biotin accounted for >50% of the total of biotin and biotin metabolites in urine. Bisnorbiotin (13-23%), biotin-d,l-sulfoxide (5-13%), bisnorbiotin methyl ketone (3-9%), and biotin sulfone (1-3%) accounted for the remainder. The percentage excretion of biotin was greater when biotin was administered intravenously and for the largest oral dose than for the 2 smallest oral doses. CONCLUSION: Our data provide evidence that oral biotin is completely absorbed even when pharmacologic doses are administered. Biotin metabolites account for a substantial portion of total urinary excretion and must be considered in bioavailability studies. We speculate that renal losses of biotin (as a percentage of the dose administered) are moderately elevated when pharmacologic doses of biotin are administered.

[Multiple carboxylase deficiency]. / Multipel karboxylasemangel.

Biotinidase deficiency and holocarboxylase synthetase deficiency are two autosomal recessively inherited disorders of biotin metabolism affecting children below the age of two years. Both cause multiple carboxylase deficiency resulting in defects of fatty acid synthesis, gluconeogenesis and amino acid catabolism. The clinical picture involves the nervous system, the skin, the respiratory system, the digestive system and the immune system, but great individual variations often makes the clinical diagnosis difficult. Early diagnosis and treatment with biotin are essential in order to prevent death from metabolic acidosis or irreversible damage to the central nervous system. Two patients with biotinidase deficiency, two patients with holocarboxylase synthetase deficiency and a review of the literature are presented. Neonatal screening for biotinidase deficiency or a higher degree of metabolic screening of the urine in children below the age of one year with seizures and unexplained clinical course are discussed.

Profound biotinidase deficiency caused by a point mutation that creates a downstream cryptic 3' splice acceptor site within an exon of the human biotinidase gene.

Biotinidase recycles the vitamin biotin from biocytin upon the degradation of the biotin-dependent carboxylases. We have identified a novel point mutation within the biotinidase gene that encodes the signal peptide in two unrelated individuals with profound biotinidase deficiency. Sequence analysis of genomic DNA from these individuals revealed a G to A transition (G100-->A) located 57 bases downstream of the authentic splice acceptor site in exon B. Although this mutation predicts a G34S substitution, it also generates a 3' splice acceptor site. Sequence of the PCR-amplified cDNA from the homozygous child revealed that all the product was shorter than that of normal individuals and was the result of aberrant splicing. The aberrantly spliced transcript lacked 57 bases, including a second in-frame ATG, that encode most of the putative signal peptide and results in an in-frame deletion of 19 amino acids. The mutation results in failure to secrete the aberrant protein into the blood. This is the first reported example in which a point mutation creates a cryptic 3' splice acceptor site motif that is used preferentially over the upstream authentic splice site. The preferential usage of the downstream splice site is not consistent with the 5'-3' scanning model, but is consistent with the exon definition model of RNA splicing.

Resolution of subependymal cysts in neonatal holocarboxylase synthetase deficiency.

Holocarboxylase synthetase deficiency is typically a biotin responsive disorder that presents with lactic acidosis, tachypnea, temperature instability, and shock in neonates (Briones et al.1989 and Fuchshuber et al. 1992). The primary defect in cases studied to date appears to be the decreased affinity of HCS for its substrate, biotin (Gompertz et al. 1971). Supplemental biotin can provide sufficient substrate to increase HCS enzymatic function and thereby permit biotinylation of the four carboxylase apoenzymes (Briones et al. 1989). We report an infant with HCS deficiency who presented with lactic acidosis, shock, and hypertonia. Subependymal cysts were identified on cranial ultrasound and subsequently confirmed by MRI. Six months following biotin supplementation, she is developmentally normal and MRI of the brain shows complete resolution of the cysts.

Biotinidase deficiency: result of treatment with biotin from age 12 years.

A boy with severe symptoms of biotinidase deficiency diagnosed at the age of 12 years showed a remarkable improvement of his neurological picture and normalization of brain magnetic resonance imaging abnormalities when prescribed oral biotin.

Ocular aspects in biotinidase deficiency. Clinical and genetic original studies.

There are two distinct forms of multiple carboxylase deficiency. A neonatal onset form is due to deficiency of holocarboxylase-synthetase. A later onset form in which neurological abnormalities are seen as well as those of the skin and hair is due to biotinidase deficiency. It is the purpose of this report to describe a patient with biotinidase deficiency who presents bilateral optic atrophy. The dosage of biotinidase enzyme in the patient's serum and in other members of his family confirms the autosomal recessive transmission of this condition.

Multiple carboxylase deficiency due to deficiency of biotinidase.

A patient with biotinidase deficiency was studied in whom the first admission to hospital for acidosis occurred at 5 years of age. Sensorineural abnormalities of the optic and auditory nerves antedated diagnosis and treatment with biotin, and these sensory losses did not resolve with treatment. The other clinical manifestations of the disease were highly responsive to biotin. Biotinidase was assayed using 14C-labeled natural substrate. The activity in the patient approximated 1% of the control level.