6-Pyruvoyl-Tetrahydropterin Synthase Deficiency (PTS)
6-Pyruvoyl-tetrahydropterin synthase deficiency is an autosomal recessive disorder caused by pathogenic variants in the PTS gene. It has been reported in patients of different ethnicities, although it has an increased prevalence in individuals of Asian ancestry. Clinical features are typically noted at birth but can present in infancy. Patients with the severe form of the disease typically develop an excess of phenylalanine in the blood (hyperphenylalaninemia). Symptoms include psychomotor retardation, abnormal muscle tone, convulsions, fatigue, irritability, hyperthermia, hypersalivation and difficulty swallowing. The mild form of 6-pyruvoyl-tetrahydropterin synthase deficiency does not include neurological symptoms and is associated with mild to moderate transient hyperphenylalaninemia. Life expectancy is variable and no genotype-phenotype correlation has been reported.
For information about carrier frequency and residual risk, please see the residual risk table.