Hyperphenylalaninemia, BH4-deficient, C

Rare autosomal recessive disorder characterized by hyperphenylalaninemia and severe neurologic symptoms (malignant hyperphenylalaninemia) including axial hypotonia and truncal hypertonia, abnormal thermogenesis, and microcephaly. These signs are attributable to depletion of the neurotransmitters dopamine and serotonin, whose syntheses are controlled by tryptophan and tyrosine hydroxylases that use BH-4 as cofactor. Patients do not respond to phenylalanine-restricted diet. HPABH4C is lethal if untreated.

Hyperphenylalaninemia, BH4-deficient, B

A disease characterized by malignant hyperphenylalaninemia due to tetrahydrobiopterin deficiency, and defective neurotransmission due to depletion of the neurotransmitters dopamine and serotonin. The principal symptoms include: psychomotor retardation, tonicity disorders, convulsions, drowsiness, irritability, abnormal movements, hyperthermia, hypersalivation, and difficulty swallowing. Some patients may present a phenotype of intermediate severity between severe hyperphenylalaninemia and mild dystonia. In this intermediate phenotype, there is marked motor delay, but no intellectual disability and only minimal, if any, hyperphenylalaninemia.

Hyperphenylalaninemia, BH4-deficient, A

An autosomal recessive disorder characterized by hyperphenylalaninemia, depletion of the neurotransmitters dopamine and serotonin, and progressive cognitive and motor deficits. Neurological symptoms are unresponsive to the classic phenylalanine-low diet.

Hyperphenylalaninemia, BH4-deficient, D

An autosomal recessive disease characterized by primapterinuria, a variant form of hyperphenylalaninemia defined by increased excretion of 7-substituted pterins in the urine. Patients with primapterinuria show an increased ratio of neopterin to biopterin in the urine, excretion of subnormal levels of biopterins, and normal levels of biogenic amines in cerebrospinal fluid. Neurologic signs are mild, present in the neonatal period only, and include hypotonia, delayed motor development and tremor.