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Malignant Hyperphenylalaninemia Tetrahydrobiopterin (BH4) Phenylalanine

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Malignant Hyperphenylalaninemia Tetrahydrobiopterin (BH4) Phenylalanine Pediat. Res. 13: 1 150-1 155 (1979) Dihydropterine reductase (DHPR) phenylketonuria malignant hyperphenylalaninemia tetrahydrobiopterin (BH4) phenylalanine Malignant Hyperphenylalaninemia-Clinical Features, Biochemical Findings, and Experience with Administration of Biopterins D. M. DANKS, P. SCHLESINGER, F. FIRGAIRA, R. G. H. COTTON. B. M. WATSON, H. REMBOLD. AND G. HENNINGS Genetics Research Unit, Royal Children S Hospital Research Foundation, and Department of Paediatrics, Universi1.y of Melbourne, Parkville, Australia (D. M. D., P. S., F. F.. R. G. H. C., B. M. W.) and Max Planck Institutfur Biochemie. Germany (H. R., G. H.) Summary has been attributed to defective production of neurotransmitters derived from hydroxylation of tyrosine and of tryptophan (3, 4). Four cases of malignant hyperphenylalaninemia (MHPA) are The results of treatment with L-dopa and 5-hydroxytryptophan described. Pretreatment serum phenylalanine levels were 1.5, 3.0, support this contention (2, 3. 7). 2.4, and 0.9 mmoles/l. Dihydropteridine reductase (DHPR) defi- Four patients with MHPA seen in Melbourne since 1963 are ciency was proven in one patient by assays on cultured fibroblastic presented. One patient has been shown to have DHPR deficiency cells and was presumed in her sibling and in another deceased and her sister is presumed to have died of this defect. Both parents patient whose parents' fibroblastic cells show approximately 50% of another baby had DHPR levels in the heterozygote range of normal enzyme activity. DHPR and phenylalanine hydroxylase suggesting DHPR deficiency as the cause of her death. The 4th deficiency were excluded by assays on liver obtained at autopsy in baby had neither PH or DHPR deficiency and defective BH4 the 4th patient. Parenteral administration of tetrahydrobiopterir synthesis is presumed. (BH4) corrected the hyperphenylalaninemia and increased the Detailed metabolic studies, especially related to BH4 are pre- levels of catecholamines and 5-hydroxy-indoles in the one patient sented in the one DHPR deficient patient diagnosed in life. The studied in life, but BH4 did not reach the cerebrospinal fluid. A 3- lowering of serum phenylalanine achieved by BH4 administration wk course of BH4 therapy had no clinical effect. Oral biopterin in this patient is proposed as a test for identification of young was absorbed and excreted in the urine, but did not alter the babies with MHPA. serum phenylalanine level. The frequency of MHPA in Australia Some of the findings have been published in preliminary form was estimated as 7 in 258 patients with phenylketonuria. (8, 9). Speculation CASE REPORTS Response of serum phenylalanine to a single injection of BH4 appears to be the most simple method of diagnosis of MHPA, CASE I applicable to all diagnosed cases of PKU, provided the G. p., female, born at full term on October 4, 1963, weighing pharmaceutical industry can be persuaded make quanti- 2.3 kg was the 1st child of Italian parents who were first cousins. ties of this compound available. Frequent convulsions commenced at 3 months. Motor develop- ment was moderately delayed, but no other abnormality was apparent. Head circumference was 37.5 cm. Serum phenylalanine The enzymic hydroxylation of phenylalanine (Phe) is believed was 1.52 mmole/liter. A low phenylalanine diet was started at 15 to comprise a complex group of reactions. wk of age" and serum vhenvlalanine. , levels were maintained be- tween 0.1-0.6 mmol/liter. However, the convulsions increased. the (1) Phe + 02+ BH4 2 Tyr + Hz0 + q-BH2 EEG showed hypsarrhythmic features and she began to lose the 1)HI'H few skills present. Progressive deterioration led to death at the age of 4 yr, 3 months. No autopsy was performed. (2) q-BH2 + NADHn + BH4 + NAD CASE 2 DHFR K. N., female, born July 2, 1968 was the 1st child of first cousin (4) 7,8-BHz + NADPH2 + BH4 + NADP parents of Australian (British) origin, delivered at 32-34 wk of The relevance of reaction (4) in vivo is particularly debatable gestation weighing 2.15 kg. Routine Guthrie test was not per- and the instability of q-BH2 makes complete delineation of the formed. At 14 wk of age, she was failing to gain weight satisfac- reactions very difficult. torily, and showed spastic quadriplegia and microcephaly (head Classical PKU involves a genetic defect of PH. Deficiency of circumference 35.5 cm). The serum phenylalanine and tyrosine DHPR has been defined recently (15, 18, 25). Some patients with were 3.0 and 0.16 mmole/liter, respectively. An EEG showed PKU have proved to have normal levels of both DHPR and PH recurring abnormal sharp transient waves. She was investigated (3, 25, 26) and presumably have a defect in de novo synthesis of' intensively for a second cause of mental retardation without BH,. These defects in BH4 synthesis and metabolism have been success. found among patients with PKU who have shown progressive Low phenylalanine diet maintained serum levels between 0.1 cerebral degeneration despite early initiation of dietary treatment. and 0.6 mmole/liter. However, she showed further gradual dete- This clinical syndrome has been named malignant hyperphenyl- rioration of neurologic function and finally died at the age of 3 yr, alaninemia (MHPA) (6). The neurologic disorder in these patients 3 months. Dietary treatment had been abandoned at 21 months. MALIGNANT HYPERPHENYLALANINEMIA Autopsy was performed and the only significant abnormalities METHODS were the extremely small size of the brain and extensive vacuola- tion within the white matter. ADMlNlSTRATlON OF PTERINS Iv injections of BH4 were prepared within I hr before admin- CASE 3 istration by dissolving the required quantity in 1 ml of distilled M. Z., male, born November 18, 1971 at full term weighing 3.43 water and filtering twice through two sterilizing 0.25 p millipore kg was the 1st child of unrelated parents of Maltese origin. filters. The injection of BH4 was followed by at least 10 ml of Detected by Guthrie test on day I I, the serum phenylalanine was 0.9% saline. 2.4 mmole/liter on day 16 when the low phenylalanine diet was Im injections were prepared in a similar manner so that BH4 commenced. Control was satisfactory with serum phenylalanine (2 mg/kg body wt) and ascorbic acid (half the mass of BH4) were levels always between 0.1 and 0.5 mmole/liter. Brief flexor spasms contained in a solution made up to 0.5 ml with 0.1 M citric acid/ and developmental delay became apparent at 5 months of age, sodium citrate buffer, pH 5. This solution was stable over a period but an EEG was normal. Intensive investigations failed to reveal of 3 wk storage a -20°C as evidenced by the fact that the UV a second cause of retardation, metabolic or infective. Unusual spectrum (265 nm peak) remained essentially unchanged. Oxida- physical features suggested the mosaic trisomy 8 syndrome; how- tion was indicated by appearance of a band at 230 nm. In practice, ever, the karyotype was normal in cultivated blood lymphocytes the longest storage was for 2 wk at -20°C. and skin fibroblasts. Oral doses were mixed with small quantity of food and admin- He deteriorated progressively with repeated major convulsions istered by spoon, or else were given via nasogastric tube. and died at 3 yr, 4 months. No autopsy was performed. All human doses were given only after informed consent of the parents. CASE 4 FIBROBLASTlC CELL CULTURE S. P., a sister of case 1, was born on March 3, 1974 at term weighing 3.12 kg. One normal boy had been born since the birth Fibroblastic cells were grown from skin biopsies in Eagle's basal of case 1. medium supplemented with 10% foetal calf serum. Cells were Guthrie test performed on day 4 gave a result of 0.4 mmole/ harvested at confluency after their 6th passage and stored frozen liter. Serum phenylalanine was 0.42 mmol/liter on day 16. Breast at -70°C after washing and pelleting. Extracts were prepared by feeding was continued and the level rose gradually to 0.9 mmol/ homogenization or freezing and thawing of approximately 8 x 10" liter by 5 wk, when a low phenylalanine diet was introduced. cells in 0.2 ml of 0.15M KCl. Cell debris was removed by centrif- Serum phenylalanine levels were maintained between 0.1-0.6 ugation at 12,000 g for 30 min and the protein concentration in mmole/liter. Progress appeared within normal limits until 8 the supernatant was measured using bovine serum albumin as a months of age, when she had six brief convulsions in 24 hr and an standard. EEG showed frequent epileptic discharges. Regression in abilities began, despite the use of anticonvulsants. Investigations per- ANALYSES RELATED TO PTERINS formed at 11 months showed gross disorganisation of the EEG DHPR activity was determined by measuring the pterin depen- and cerebral atrophy in a pneumoencephalogram. Diet was dis- dent oxidation of NADHL,at 340 nm and 37°C using an optimized continued because the serum phenylalanine rose to only 0.6 assay (10) based on the method described by Nielsen et al. (19). mmole/liter on normal diet. Pterins and fluorescent compounds in urine were studied semi- At this stage, the idea of a fault in BH, supply was first quantitatively by high voltage electrophoresis and quantitated by entertained. TLC (27). A series of trials of administration of BH4 caused biochemical ~rithidiaactive pterins in plasma, urine, and cerebrospinal fluid changes described later in this paper, but a 3-wk course of BH4 were measured by previously described methods (I I). and a similar length course of neurotransmitter replacement ther- apy produced no clinical improvement. Both treatments were NEUROTRANSMITTERS AND OTHER METABOLITES given at a stage of very severe brain damage.
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