Clinical and molecular findings in Thai patients with isolated methylmalonic acidemia.

Isolated methylmalonic acidemia (MMA) is a genetically heterogeneous organic acid disorder caused by either deficiency of the enzyme methylmalonyl-CoA mutase (MCM), or a defect in the biosynthesis of its cofactor, adenosyl-cobalamin (AdoCbl). Herein, we report and review the genotypes and phenotypes of 14 Thai patients with isolated MMA. Between 1997 and 2011, we identified 6 mut patients, 2 cblA patients, and 6 cblB patients. The mut and cblB patients had relatively severe phenotypes compared to relatively mild phenotypes of the cblA patients. The MUT and MMAB genotypes were also correlated to the severity of the phenotypes. Three mutations in the MUT gene: c.788G>T (p.G263V), c.809_812dupGGGC (p.D272Gfs*2), and c.1426C>T (p.Q476*); one mutation in the MMAA gene: c.292A>G (p.R98G); and three mutations in the MMAB gene: c.682delG (p.A228Pfs*2), c.435delC (p.F145Lfs*69), and c.585-1G>A, have not been previously reported. RT-PCR analysis of a common intron 6 polymorphism (c.520-159C>T) of the MMAB gene revealed that it correlates to deep intronic exonization leading to premature termination of the open reading frame. This could decrease the ATP:cobalamin adenosyltransferase (ATR) activity resulting in abnormal phenotypes if found in a compound heterozygous state with a null mutation. We confirm the genotype-phenotype correlation of isolated MMA in the study population, and identified a new molecular basis of the cblB disorder.

Novel mutations found in two genes of thai patients with isolated methylmalonic acidemia.

Molecular genetic analysis of three patients diagnosed with isolated methylmalonic acidemia (MMA) revealed that one was mut (0) MMA, with a mutation in the MUT gene encoding the L: -methylmalonyl-CoA mutase (MCM), and two were cblB MMA, with mutations in the MMAB gene required for synthesizing the deoxyadenosylcobalamin cofactor of MCM. The mut (0) patient was homozygous for a novel nonsense mutation in MUT, p.R31X (c.167C --> T), and heterozygous for three previously described polymorphisms, p.K212K (c.712A --> G), p.H532R (c.1671A --> G), and p.V671I (c.2087G --> A). The new MMAB mutation, p.E152X (c.454G --> T), was found to be homozygous in one cblB patient and heterozygous in the other patient, who also had four intron polymorphisms in this gene.

Homocystinuria in Thai patient--Phramongkutklao Hospital experience.

Homocystinuria is a rare autosomal recessive disorder of amino acid metabolism. Classic (type I) homocystinuria is the most common type and occurs as a consequence of a deficiency of cystathionine-b-synthase, producing increased blood and urine homocysteine. The authors report a 15-year-old Thai male who presented with generalized tonic-clonic seizures from superior sagittal sinus thrombosis, bilateral downward subluxation of ocular lenses (ectopia lentis), Marfanoid habitus, osteoporosis, attention deficit and hyperactivity disorder. Urine metabolic screening was positive for cyanide nitroprusside test. Levels of plasma homocysteine and methionine were elevated. The clinical and laboratory findings in this case are consistent with the diagnosis of "type I" or "classical homocystinuria". The treatment was started with a low methionine diet, vitamin B6 or pyridoxine, folic acid, anticonvulsants, antithrombotic treatment and calcium supplementation. Genetic counseling was provided to the family with the recurrent risk of 25%. Definite diagnosis by enzyme assay or mutation analysis and also prenatal diagnosis are not established in Thailand.

Glycogen storage diseases in Thai patients: Phramongkutklao Hospital experience.

There are 3 cases of liver type glycogen storage diseases. All of them presented with protruding abdomen, failure to thrive, doll face and mark hepatomegaly. Laboratory findings were hypoglycemia, metabolic acidosis, abnormal liver function test, hyperlipidemia and prolonged bleeding time in GSD Ia. GSD III has no hypoglycemia and borderline hyperuricemia. Glucagon stimulation test helps to differentiate typing. The aim of treatment is to prevent hypoglycemia, suppress lactic acid production, decrease blood lipid and uric acid levels and enhances statural growth by uncooked cornstarch. Complications such as epistaxis and suspected liver adenoma have to be closely followed up. Genetic counseling for both types GSD are autosomal recessive with recurrence risk of 25%. Prenatal diagnosis by enzymes assay or molecular diagnosi are not available in this hospital.