Overview
Tetrahydrobiopterin (BH4) deficiency is a congenital metabolic disorder that causes hyperphenylalaninaemia and progressive CNS disorders.
Immunology
More than 300 cases of PTPS deficiency have been reported worldwide, with 32 cases diagnosed in Japan.
Cause
Mutations in the PTS gene result in a deficiency of BH4 due to a deficiency of 6-pyruvoyl tetrahydropterin synthase (PTPS).
Symptoms
Hyperpheaemia is present from the neonatal period. It is often recognised by the onset of decreased muscle tone in the trunk and tubular rigidity of the limbs, as well as high-pitched whimpers and sometimes brief convulsions. It is generally detected and treated before the onset of the disease by neonatal mass screening, so there are no actual clinical signs.
Diagnosis
Generally detected by neonatal mass screening.
Genetic testing.
Medical treatment
Neurotransmitter replacement therapy is used to control blood phenylalanine levels at the same time.
Treatment should be continued throughout life, as failure to do so can lead to death in adulthood.
References
Intractable Disease Information Centre: https://www.nanbyou.or.jp/wp-content/uploads/kenkyuhan_pdf2014/gaiyo051.pdf
