[Phenylketonuria with adult-onset neurological manifestation].

We report a male patient with phenylketonuria (PKU) who developed multisystem neurological manifestation in his fourth decade. He was born in 1957 when a neonatal mass screening had not been available. His neuropsychological development was entirely normal and he was a good athlete during his high school days. He was in good health until the age of 32, when his vision was blurred. In four months his gait progressively deteriorated to bind him to a wheel chair. On physical examination he had red hair and gray eyes. IQ was 68. Visual field showed concentric narrowing and his visual acuity was 0.2/0.3 (2.0/2.0). The limbs were spastic and weakened. He complained of pain in the extremities. He suffered from pollakisuria. Routine blood tests and CSF findings were normal. He was also found to be normal in peripheral nerve conduction studies and central conduction studies of SEP and VEP. EEG showed diffuse slowing in background activities. T2-weighted MRI of the head revealed widespread high-intensity areas in the deep white matter especially in bilateral occipital lobes. Serum aminogram disclosed the remarkably elevated phenylalanine (Phe) level to 1663 nmol/ml (normal range 50-90) and reduced tyrosine. Urinary secretion of endogenous tetrahydroxy-biopterin (BH4; coenzyme of Phe hydroxylase) remained in a normal range, and oral administration of 100 mg/kg of BH4 failed to normalize the serum Phe level. Despite a strict dietary control (oral intake of Phe less than 0.5 g/day), the serum Phe level remained high around 500 nmol/ml and his neurological deficits still deteriorated.(ABSTRACT TRUNCATED AT 250 WORDS)