Intellectual development in 12-year-old children treated for phenylketonuria.

Intelligence and achievement test scores were evaluated for 95 12-year-old children with phenylketonuria who had begun dietary therapy during the neonatal period. Dietary control of blood phenylalanine below 900 mumol/L was maintained beyond age 10 years in 23 children; 72 others had blood phenylalanine persistently above that level at ages ranging from 18 months to 10 years. Test scores at age 12 years were negatively correlated with the age at initiation of diet and with blood phenylalanine levels from ages 4 to 10 years, and positively correlated with parent IQ scores and the age at loss of dietary control. Children who maintained phenylalanine levels below 900 mumol/L beyond age 10 years showed no deficits in test scores, except for arithmetic, the scores of which declined between ages 6 and 12 years in 90% of the children in this study. These data strongly support a recommendation that dietary restriction of phenylalanine should be maintained through adolescence.

Biopterin synthesis defects: problems in diagnosis.

Hyperphenylalaninemia due to a biopterin synthesis defect was detected in an infant with decreased biopterin and increased neopterin levels in plasma and urine. Tetrahydrobiopterin (BH4) administration normalized plasma phenylalanine levels. CSF biopterin and neurotransmitter metabolite levels were normal and with the infant's normal growth and development suggest that the defect in biopterin synthesis did not affect CNS biopterin metabolism. Comparison of plasma and urine pterin levels from this patient with levels reported in patients who have neurologic complications fails to reveal differences that would distinguish patients at risk for neurologic problems. CSF pterin and neurotransmitter levels may correlate with neurologic function in these patients. CSF pterin and neurotransmitter determinations should be performed prior to initiation of neurotransmitter precursor and BH4 replacement therapies in patients who were determined to have biopterin synthesis defect(s).

Biotin-responsive in vivo carboxylase deficiency in two siblings with secretory diarrhea receiving total parenteral nutrition.

Two siblings with a congenital syndrome of secretory diarrhea and seizures developed progressive skin rash, alopecia, and mucocutaneous candidiasis while receiving biotin-free total parenteral nutrition. Abnormally low urinary biotin excretion was associated with these clinical findings, but the serum concentration of biotin was within the normal range. There was also increased urinary excretion of lactic acid, 3-hydroxyisovaleric acid, 3-hydroxypropionic acid, and 3-methylcrotonylglycine. The younger of the two children subsequently died with severe metabolic acidosis. In the oder sibling, intravenous treatment with biotin (200 micrograms/day) resulted in resolution of the organic aciduria. A larger dose (10 mg/day) appeared to be required for rapid improvement in the skin lesions. These cases suggest that clinically significant biotin deficiency can occur in patients with chronic diarrhea receiving biotin-free total parenteral nutrition.

EEG in phenylketonuria. Attempt to establish clinical importance of EEG changes.

To determine the importance of an abnormal EEG in phenylketonuria (PKU), we reviewed 137 EEGs from 48 patients with PKU. Patients were divided into three groups: group 1 (n = 14) had only normal EEGs, group 2 (n = 20) had only abnormal EEGs, and group 3 (n = 14) initially had normal EEGs that later became abnormal. The most common EEG abnormality was focal paroxysmal discharge. Patients in group 2 started treatment at a later age an had a greater frequency of seizures and mental retardation. Phenylalanine levels greater than 20 mg/dL were more often associated with abnormal EEGs. Older patients were more likely to have abnormal EEGs; 78% of the 41 patients who had EEGs at age 6 or older had abnormal records, whereas only 15% of the 26 patients who had EEGs before the age of 6 had abnormal records. Conventionally treated patients with classic PKU and normal EEGs in infancy may have abnormal EEGs when retested later even though they remain on a restricted diet. Although not usually associated with clinical deterioration, abnormal EEGs may unveil the presence of CNS dysfunction even when a child is in satisfactory clinical condition.

Excretion of pterins in phenylketonuria and phenylketonuria variants.

Total urinary biopterin (B), neopterin (Ne) and monapterin (M) were measured in 25 healthy newborns, children and adults, in 49 patients with phenylketonuria (PKU) assumed to be deficient in phenylalanine-4-hydroxylase (PH), in 7 patients with dihydrobiopterin synthetase (DHBS) deficiency and in 4 patients with dihydropteridine reductase (DHPR) deficiency. Excretion of Ne based on creatinine (Ne/C) was 6.6 times higher in healthy newborns than in adults, suggesting a slow maturation of DHBS activity. Newborns excreted more Ne than B and adults more B than Ne (32 and 72% B of the sum of B + Ne, respectively). In all cases, excretion of M was 4-15% of that of Ne. PH deficient patients excreted more B and Ne than healthy controls and again, newborns more than older children. In individual patients, excretion of pterins correlated with phenylalanine (Phe) concentration in plasma; plasma Phe of different patients did not correlate well with excretion of pterins. In PKU variants with deficiency of tetrahydrobiopterin (BH4), extreme pterin patterns were observed: in DHBS- and DHPR-deficient patients, less than 3.5 and more than 81% B were found, respectively. All 30 samples from these patients investigated could be distinguished from those of PH-deficient patients and controls by a two-dimensional plot of % B versus B/C. Thus it seems likely that PKU variants due to BH4 deficiency could be detected early and differentiated by measurement of urinary B, Ne and C. This was exemplified already in one case. - In urine of patients with DHBS deficiency, high concentrations of 3'-hydroxysepiapterin were found in addition to Ne.

Bacterial meningitis and sensorineural hearing loss: a prospective investigation.

The objectives of the present investigation are as follows: to prospectively assess the incidence of sensorineural hearing loss (SHL) associated with bacterial meningitis; to evaluate the onset and degree of SHL; and to describe the audiometric pattern. Forty-seven patients were studied otologically and audiologically. The incidence of SHL was 11%. Late onset of SHL was not observed, however, one patient demonstrated a probable progressive hearing loss. Both bilateral and unilateral hearing loss were noted. The degree of hearing loss varied from mild to profound, with no consistent audiometric pattern. Intensive follow-up on one hearing-impaired patient included temporal bone polytomograms. Obliterative labyrinthitis is detailed. Antibiotic treatment and laboratory data are evaluated. Suggestions are provided for the post-meningitic course.

Folate distribution in cultured human cells. Studies on 5,10-CH2-H4PteGlu reductase deficiency.

We have studied the distribution of folate coenzyme forms in cultured human fibroblasts from control lines and from lines derived from nine patients representing all of the published reports of 5,10-CH(2)-H(4)PteGlu reductase deficiency. Based on mobility on DEAE-Sephadex and differential microbiological assay the major folate fractions in extracts of human fibroblasts were 5-CH(3)-H(4)PteGlu, 10-CHO-H(4)PteGlu, and 5-CHO-H(4)PteGlu with smaller fractions, which included 5-CH(3)-H(2)PteGlu, 10-CHO-PteGlu, and H(4)PteGlu. Evidence that the 5-CHO-H(4)PteGlu may have been derived from 5,10-CH=H(4)PteGlu during extraction is presented. In most of the mutant fibroblasts the absolute concentration of 5-CH(3)-H(4)PteGlu was lower than in control cells but the proportion of intracellular folate which was 5-CH(3)-H(4)PteGlu was strikingly lower in mutant cells when determined by chromatography or differential microbiological assay. In both control and mutant cells most of the 5-CH(3)-H(4)-PteGlu was polyglutamate. The proportion of intracellular folate which was polyglutamate was similar in control and mutant cells. A direct relationship was observed between the proportion of cellular folate which was 5-CH(3)-H(4)PteGlu, and both the clinical severity of this disorder and the residual enzyme activity indicating that the distribution of different folates may be an important control of intracellular folate metabolism. These studies indicate that 5,10-CH(2)-H(4)PteGlu reductase is the only significant intracellular pathway for the generation of 5-CH(3)-H(4)PteGlu, that the activity of this enzyme regulates the level of this folate in control and mutant cells under conditions of culture used here, that the majority of intracellular folate is in the polyglutamate form, and that the relative distribution of folates may control folate metabolism by interaction in the various folate reactions.

Hyperphenylalaninemia due to a deficiency of biopterin. A variant form of phenylketonuria.

We studied the components of the hepatic phenylalanine hydroxylating system in a child with phenylketonuria who showed substantial neurologic impairment despite early dietary control of elevated blood phenylalanine levels. Phenylalanine hydroxylase, dihydropteridine reductase and dihydrofolate reductase activities were normal. In contrast the level of hydroxylation cofactor, tetrahydrobiopterin, in liver was only 10 per cent of normal. In addition to this hepatic deficiency, serum and urinary levels of biopterin-like compounds were low, and the serum biopterin did not increase in response to a phenylalanine load as it does in normal and phenylketonuric subjects. The phenylalanine hydroxylase activity in this child, as determined by an in vivo tritium-release assay, was 2.3 per cent of the normal value. These results indicate that the child suffers from a variant form of phenylketonuria--a deficiency of a functional phenylalanine hydroxylating system secondary to a defect in biosynthesis of biopterin.

Detection of homozygotes and heterozygotes with methylenetetrahydrofolate reductase deficiency.

Specific enzyme assay is required for the diagnosis of homocystinuria due to methylenetetrahydrofolate reductase deficiency. A rapid and accurate method has been developed using "pure" peripheral lymphocyte preparations. Triplicate determinations showed highly reproducible results. With the use of the mean of triplicate determinations in the presence of flavinadenine dinucleotide, there was complete segregation among the homozygotes, heterozygotes, and normal subjects. This method provides a rapid diagnosis in affected subjects and a simple means for the determination of heterozygotes for genetic counseling.