6-Pyruvoyltetrahydropterin Synthase

What is 6-Pyruvoyltetrahydropterin Synthase?

6-Pyruvoyltetrahydropterin Synthase is a rare disease. It is also known as 6-pyruvoyl-tetrahydropterin Synthase Deficiency Biopterin deficiency Hyperphenylalaninemia, Tetrahydrobiopterin-deficient, Due To Pts Deficiency PKU III Pts Deficiency.

The newborn screening programme is likely to show a 1 in 10,000 incidence of hyperphenylalaninemia. In this category, 1-2% will have a pterin co-factor deficiency. The hyperphenylalaninaemia under discussion here is due to biopterin (BH2) deficiency. Patients show progressive neurological deterioration, being at first hypotonic but then developing spasticity and extrapyramidal signs. Some adult patients have considerable dystonia and blepharospasm, and diurnal fluctuation has been noted (Hanihara et al., 1997).
The levels of BH2 are low, as are levels of BH4 (l-erythrotetrahydrobiopterin) which is a product of BH2. The lack of BH4 impairs the hydroxylation of phenylalanine, tyrosine and tryptophan. The specific diagnosis depends on the assay of the relevant enzyme in liver and fibroblasts.
See also `guanosine triphosphate cyclohydrolase 1 deficiency', an inborn error of BH4 syntheses, and `dihydropteridine reductase (DHPR) deficiency' which results in hyperphenylalaninaemia due to DHPR's role in catalysing the regeneration of BH4. Both conditions have a similar phenotype to the condition under discussion. The gene has been mapped to 11q22.3-q23.3 (Thony et al., 1994) and mutations have been identified. A C259C mutation is common in the Chinese (Liu and Hsiao, 1996, and N52S and P87S are common in Taiwanese (Chien et al., 2001). Up to 2001, about 33 different mutations had been identified and there was no clear correlation between genotype and phenotype (Dudesek et a., 2001).

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* This information is courtesy of the L M D.

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What gene changes cause 6-Pyruvoyltetrahydropterin Synthase?

The syndrome is inherited in the following inheritance pattern/s:

Autosomal Recessive - Autosomal recessive inheritance means an affected individual receives one copy of a mutated gene from each of their parents, giving them two copies of a mutated gene. Parents, who carry only one copy of the gene mutation will not generally show any symptoms but have a 25% chance of passing the copies of the gene mutations onto each of their children.

In some cases, a genetic syndrome may be the result of a de-novo mutation and the first case in a family. In this case, this is a new gene mutation that occurs during the reproductive process.

OMIM Number - 261640 (please check the OMIM page for updated information)

The syndrome can be caused by mutations in the following gene/s location/s:
PTS - 11q23.1

What are the main symptoms of 6-Pyruvoyltetrahydropterin Synthase?

The typical symptoms of the syndrome are:
Excessive daytime somnolence, Progressive neurologic deterioration, Rigidity, Microcephaly, Autosomal recessive inheritance, Seizure, Poor suck, Parkinsonism, Choreoathetosis, Ataxia, Bradykinesia, Recurrent fever, Dysphagia, Dystonia, Small for gestational age, Excessive salivation, Muscular hypotonia of the trunk, Irritability, Tremor, Intellectual disability, progressive, Hyperphenylalaninemia, Hyperreflexia, Global developmental delay

How does someone get tested for 6-Pyruvoyltetrahydropterin Synthase?

The initial testing for 6-Pyruvoyltetrahydropterin Synthase can begin with facial genetic analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the type of genetic testing needed. A consultation with a genetic counselor and then a geneticist will follow.

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.

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