Long-term follow-up of 12 patients with the late-onset variant of argininosuccinic acid lyase deficiency: no impairment of intellectual and psychomotor development during therapy.

To date, two variants of argininosuccinic acid lyase deficiency, the second most common enzymatic defect of the urea cycle, have been described. Most of the previous studies reported on outcomes involving neurological and intellectual impairment in affected children. This study is the first to demonstrate that the physical and mental development of such children can be normal and adequate for their age if they are treated with a low-protein diet and/or arginine supplements. Since 1973, 12 Austrian children suffering from argininosuccinic acid lyase deficiency have been detected in the Austrian Neonates Screening Program and could have been followed up. After confirmation of diagnosis, all the children were administered a daily arginine supplement (3 to 4 mmol/kg per day) in conjunction with either a normal diet or a special diet in which protein intake was restricted to 1.2 to 1.5 g/kg per day. Routine checks, including physical examination, determination of biochemical parameters, and IQ tests, were performed so the further development of these 12 patients with respect to treatment could be observed. It can be concluded that early treatment of partial argininosuccinic acid lyase deficiency results in normal intellectual and psychomotor development.

[21 years "Austrian Program for Early Detection of Congenital Metabolic Abnormalities." Did the screening programs also contribute scientific knowledge?]. / 21 Jahre "Osterreichisches Programm zur Früherfassung angeborener Stoffwechselanomalien". Brachten die Screening-Programme auch wissenschaftliche Erkenntnisse?

Before the introduction of the programme for the early detection of inborn errors of metabolism the discovery of the biochemical abnormality was merely the proof of a diagnoses based on characteristic features. Neonatal screening inverted the process and the biochemical anomaly became primary marker and symptoms were prevented by treatment. In reality, the subsequent development of symptoms was uncertain. In this way a great number of hitherto unknown metabolic anomalies was discovered. Screening methods for the first time allowed correct determination of the incidence of inherited disorders in different population. Important differences were uncovered intra- and internationally. Screening centres performing psychometry not only in homozygote patients, but also in heterozygote parents found that the heterozygotes for phenylketonuria (PKU) in spite of normal blood phenylalanine levels, are slightly subnormal intellectually. This is true also for early- and satisfactory-treated homozygotes. Increased intracellular phenylalanine concentrations in both could explain this slight intellectual subnormality which is, apparently, independent of the blood level. At least three treatment centres observed a decrease in IQ of 9 to 13 points between 1 and 8 years of age in early- and well-treated PKU patients being mostly still in the normal range. The IQ curves are parallel for these tree centres and independent of the age of diet discontinuation.

[Toxoplasmosis screening of pregnant patients in Austria]. / Toxoplasmose-Screening bei Schwangeren in Osterreich.

The frequency of congenital Toxoplasma infection is strictly correlated with the frequency of Toxoplasma primary infection in child bearing age. The latter corresponds directly to the increase of contamination rate in the normal population between 20 and 40 years of age, if determined with a sensitive method detecting also low antibody concentrations with certainty (Sabin-Feldman-dye test). In four representative studies the relation was 0.52 conversions id est 0.26 congenital infection per 1 000 per 1% contamination increase. Most congenitally infected children seem normal in newborn age. Follow up studies for long enough periods--many years!--have shown that practically all these children develop sequelea, chorioretinitis and/or cerebral defects. Postnatal treatment does not influence this evolution but preventive treatment in pregnant women selected by serological screening uncovering primary infections does prevent fetal infections with their consequences.

Intracellular phenylalanine and tyrosine concentration in homozygotes and heterozygotes for phenylketonuria (PKU) and hyperphenylalaninemia compared with normals.

Assuming adequate technique, determinations of intracellular phenylalanine and tyrosine concentrations in lymphocytes are very reproducible. The concentrations found in this study (1981) in five homozygotes and five obligate heterozygotes for PKU and seven normals, are identical with the corresponding concentrations found in 1979 in 13 homo- and 19 obligate heterozygotes for PKU and 26 normals. The intracellular concentrations in six homo- and five heterozygotes for hyper-Phe, as determined in the present study, are intermediate between the concentrations found in PKUs and normals in the present and the former study. As in PKUs, there is no difference between homo- and heterozygotes for hyper-Phe. The hypothesis of an intracellular threshold concentration for phenylalanine triggering the production of a toxic metabolite, could explain the severe brain damage observed in untreated PKU-homozygotes, the slight damage in well-treated PKU-homozygotes and in PKU-heterozygotes, and the absence of damage in hyper-Phe homozygotes (and heterozygotes). Also the difference in brain function between homozygotes for both conditions (PKU-treated), can be understood in spite of comparably elevated extracellular phenylalanine concentrations in young patients.

[Screening for congenital hypothyroidism in Austria (author's transl)]. / Screening auf angeborene Hypothyreose in Osterreich.

Screening for Hypothyroidism is part of the Austrian Newborn Screening for Inborn Errors and centralized (ca. 85.000 births/year). It began 1976 in 2 provinces and covers the whole country since 7.6.1978. Primary T4 and selective TSH on 3 mm discs is used. Control frequency is 0.14%, the frequency of permanent primary hypothyroidism is 1:4724. Hypothyroidism seems more frequent in Western- then in Eastern- Austria (1:4227 v. 1:5422). Hypothyroid babies are almost double as frequently born in September until November then in other quarters of the year. In 47 cases 28 male compare with 19 female. In 4 cases with low T4 and high TSH in the initial Tests T4 became normal within 13--27 days while TSH remained high.

[12 years Austrian newborn screening for inborn errors of metabolism. Results with special reference to phenylketonuria, hyperphenylalaninemia and histidinemia (author's transl)]. / Zwölf Jahre österreichisches Programm zur Früherfassung angeborener Stoffwechselanomalien. Ergebnisse unter besonderer Berücksichtigung von Phenylketonurie, Hypearphenylalaninämie und Histidinämie.

The Austrian Screening Program performed during the last 12 years 5,833.381 tests in 1,003.841 newborns to detect at last 10 different disorders. 225 cases were uncovered: 81 PKU, 1 Dihydropteridine-Reductase-Deficiency, 37 Hyperphenylalaninemias of long duration, 23 Galactosemias by Transferase deficiency, 6 by Kinase deficiency, 1 Leucinosis, 1 Homocystinuria, 54 Histidinemias, 2 Arginino-Succinic-Acidurias, 3 alpha-1-Antitrypsin-Inhibitor-Deficiencies, 15 Hypothyroidism as well as 1 Phosphoglucomutase-Deficiency. Since 1976 97% of all live births were tested. Except in Hypothyroidism in Austria also treatment and follow-up are centralized. This makes a higher treatment quality and important observations possible. In PKU-patients there is a decline in EQ/IQ between 1 and 6 to 8 years of age of 13 points in average (105--92). This decline can not be correlated with treatment introduction age (26.4 days) and treatment quality. Since also the parents IQ's are significantly below the IQ's of a recent control group and mothers IQ are paralleling the IQ's of their PKU children the decline seems to be a phenylalanine-blood-level-independent phenomenon. Also one quarter of the patients with Histidinemia shows the same IQ decline. The difference between Bühler-Hetzer and Kramer results at 4 years of age seem to have prognostic value. Comparison for 1978 of the expenses of the total screening plus the one of diet in 59 PKU patients already psychometrically tested (average IQ 100) with the expense for institutionalisation of the same 59 shows the former 5 million A.S. lower.

[Psychometry and psychological observations in early treated children with phenylketonuria (PKU) during 12 years (author's transl)]. / Psychometrie und psychologische Verlaufsbeobachtungen and 63 frühbehandelten Kindern mit Phenylketonurie (PKU).

Among 81 PKU's uncovered until 1978/12/31 63 were 1 to more than 8 years old so at least once up to 4 times psychometrically examined. Although the IQ's at 8 years were still in the normal rang there was a slight but between 6 and 8 years statistically significant (p less than 0.01) decline in IQ. There is no correlation between this decline and the diet introduction age (26--29, average 26,4 days) nor the diet discontinuation age (4 to 8 years) and the predominantly good diet quality. But there were relations to the parental IQ. It seems remarkable that the centers of London and Warschau report declines of the same extent at approximately the same ages in spite of different diet discontinuation ages. The IQ losses in the patients derive almost totally from losses in the verbal part of the tests. Also the slight but statistically significant IQ deficits demonstrated in heterozygotes for PKU (parents) arise almost entirely from the verbal quotient. It is supposed that both observations are phenylalanine blood level independent phenomena. The demonstration of statistically highly significant augmentations of intracellular phenylalanine (and tyrosine) in heterozygotes and homozygotes for PKU may indicate an explanation. Our early treated children with PKU show the same weakness in concentration, perseverance and cognitive abilities (mathematics, orthography, picture coordination) as observed by other centers. These disabilities are largely IQ independent, influence school work adversely but can be improved by psychological promotion. Children with hyperphenylalaninemia do not show the slight decline in IQ nor the specific disabilities.

[Intracellular concentration of phenylalanine, tyrosine and alpha-amino butyric acid in 13 homozygotes and 19 heterozygotes for phenylketonuria (PKU) compared with 26 normals (author's transl)]. / Intrazelluläre Konzentrationen von Phenylalanin, Tyrosin und alpha-Aminobuttersäure bei 13 Homozygoten und 19 Heterozygoten für Phenkyletonurie (PKU) sowie 26 Normalen.

Intracellular concentrations for phenylalanine, tyrosine, alpha-amino butyric acid and 7 other amino acids (glycine, alanine, valin, cystin, methionine, iso-leucin, leucin) were measured in lymphocytes of 13 homozygotes and 19 heterozygotes for phenylketonuria as well as in lymphocytes of 26 normals. Intracellular concentrations for phenylalanine, tyrosine and alpha-amino butyric acid were significantly higher in homo- and heterozygotes than in normals (p less than 0,001--p less than 0,01). For the other 7 amino acids there were no or only questionable differences. Between homo- and heterozygotes there was no difference in any of the amino acids. Intracellular phenylalanine: tyrosine ratio was essentially the same in all three groups of individuals. There was no correlation between intracellular phenylalanine above or below 10 nmol/10(6) cells and IQ in heterozygotes. The same is true for phenylalanine: tyrosine ratio greater or smaller than 1. In Homozygotes there was no correlation between intracellular phenylalanine and age -- to whom DQ/IQ is correlated. There was no significant difference in intracellular phenylalanine between homozygotes with blood levels above and below 908 mumol/l (15 mg/100 ml) at the time of blood sampling and no correlation between intra- and extra-cellular phenylalanine concentrations. Among the 26 normals there were only 2 with intracellular phenylalanine above 10 nmol/10(6) cells, both showing phenylalanine loading test curves suspicious for heterozygosity. The results are discussed and important functions of the cell wall supposed. An abnormal unknown intracellular metabolite being the real noxious agent could explain the incomparably different degree of brain dysfunction in individuals with equal though elevated intracellular phenylalanine concentrations i.e. homozygotes and heterozygotes for PKU.

[Hypergalactosemia in newborns as uncovered by the Austrian screening program in 12 years (author's transl)]. / Hypergalaktosämien im Neugeborenenalter durch das Osterr. Programm zur Früherfassung angeborener Stoffwechselanomalien in 12 Jahren aufgedeckt.

The Austrian Screening Program examined during 12 years 1,002.424 newborns and uncovered 23 cases of Galactosemia by Transferase deficiency, 6 by Kinase deficiency as well as 1 case of Phosphoglucomutase deficiency, 1 of porto-caval shunt and 1 congenital liver cirrhosis. Among the 23 Transferase deficiencies 18 took a fulminating course and 8 of these died. Since introduction of exchange transfusion as emergency treatment and acceleration of the screening procedure only 2 among 11 have died. Half of all Galactosemia cases, Transferase and Kinase, show already at the first examination (2. week) a cataract which however is reversible. In contrast to Kinase deficiency all cases of Transferase deficiency exhibit mental retardation if they grow older. Since treatment is early (9, 7 days), easy and the IQ already at 4 years 10 points below that of treated PKU's of same age a congenital brain damage has to be considered. Galactosemia by Transferase deficiency is in Western-Austria significantly more frequent than in Eastern-Austria. 17 boys compare with 6 girls. Among 6 cases of Galactosemia by Kinase deficiency 1 belonged to a Gippsy and 2 to Yugoslavian guest worker families. The 23 cases with Transferase deficiency had 45 siblings among whom 11 also were galactosemic. In 8 sibships the clinical course was of the same typ, but in 1 family one child showed the fulminating the other the subacute course.

Intracellular phenylalanine and tyrosine concentrations in 19 heterozygotes for phenylketonuria (PKU) and 26 normals. Do the higher values in heterozygotes explain their lowered intellectual level?

Intracellular phenylalanine and tyrosine was determined in lymphocytes of 10 heterozygotes (parents) for PKU and in 26 randomly collected apparently normal persons. In cells from the heterozygotes the concentrations of both phenylalanine and tyrosine were higher than in those from the normals, the difference being statistically highly significant. It is argued that this could be responsible for the slight, though statistically significant, intellectual inferiority of heterozygotes for PKU.

Intellectual level (IQ) in heterozygotes for phenylketonuria (PKU). Is the PKU gene also acting by means other than phenylalanine-blood level elevation?

There is a statistically significant difference in the IQ's of PKU and histidinemia parents. The difference is due entirely to the verbal part of the Hamburg-Wechsler test. There is no significant difference in performance. The heterozygous state of histidinemia does not seem to bear an intellectual (evolutionary) advantage, since the IQ's of histidinemia parents show the same distribution as a normal population. In early and mostly well-treated PKU patients, the same slight deficit in verbal IQ appears with increasing age (changing test methods). These patients, simultaneously tested at 4 years of age with the Bühler-Hetzer and Kramer tests, exhibit a statistically significant difference between the results in favor of the less verbal Bühler-Hetzer. Since heterozygots for PKU never have elevated phenylalanine blood levels, and because tryosine deficiency as argued by others seems highly improbable, we believe that the PKU gene has a more direct action on (or in) at least certain ganglion cells, lowering the verbal IQ slightly but significantly. This action is not reflected by phenylalanine increase in the extracellular space in heterozygots and is not abolished by dietary treatment in homozygous PKU patients. The major damage in PKU patients must be due to chronic phenylalanine poisoning, which deteriorates cells and/or functions on a much larger scale, because it can be easily prevented by decreasing the phenylalanine blood level with correct dietary treatment.

[The IQ of heterozygotes for phenylketonuria (PKU). indication of a blood phenylalanine-independent action of the PKU mutant (author's transl)]. / Uber das Intelligenzniveau (IQ) von Heterozygoten für Phenylketonurie (PKU). Hinweis auf eine Phenylalaninblutspiegel-unabhängige Wirkung der PKU-Mtante.

The IQ of parents of phenylketonuria-(PKU-)affected children is lower than that of parents with histidinemia-affected children (control group). The difference arises almost entirely from the verbal part of the Hamburg-Wechsler test. The IQ of the parents with histidinemia-affected children shows the same distribution as that of the normal population; heterozygosity for this condition does not appear to confer any intellectual advantage. In PKU patients treated at an early age and apparently adequately, a slight, but significant decrease in IQ becomes apparent between the ages of 6 and 8 years. This slight decrease also refers mainly to the verbal IQ. At 4 years of age all PKU patients are tested with Bühler-Hetzer, as well as the Kramer test. There is a significant difference between the results in favour of the Bühler-Hetzer test, which is much less verbal. Since heterozygotes for PKU never show elevated blood phenylalanine levels and, moreover, prenatal tyrosine deficiency, as argued by others, seems highly improbable, it is supposed that the PKU gene has a more direct influence on certain ganglion cells at least, with a consequent slight, but significant lowering of the verbal IQ in heterozygotes and satisfactorily-treated homozygotes for PKU. A slightly increased intracellular phenylalanine concentration in heterozygotes and apparently adequately-treated homozygotes need not to be reflected in raised blood levels and this could be an explanation for the observed IQ lowering. But it should not be overlooked that by far the greatest part of damage in PKU patients is caused by chronic phenylalanine poisoning which is well preventable by correct dietary treatment.

[Screening of newborns for argininosuccinase deficiency. First experiences in Austria (author's transl)]. / Erste Erfahrungen mit einem Neugeborenen-Blutscreening auf Argininosuccinasemangel in Osterreich.

In 1973, the screening for argininosuccinase deficiency was taken up by the Austrian Metabolic Disorder Screening Program using Murphey's enzyme auxotroph test. Amongst 293802 tested newborn infants, two cases of this disorder could be identified, which under protein restricted diet had a normal development until now. Inhibition zones due to antibiotic or desinfectant contamination do not disturb test evaluation in contrast to the bacterial inhibition assay (Guthrie test). The frequency of "false positive" results is small (0.05%) as well as additional work for this test procedure. So screening for argininosuccinase deficiency seems to be a useful completion of a neonatal blood screening program.