A Case of Dihydropteridine Reductase Deficiency

Tetrahydrobiopterin (BH4) deficiency is caused by mutations in genes encoding enzymes involved in the synthesis and regeneration of BH4. The condition is usually accompanied by hyperphenylalaninemia (HPA) and deficiency of neurotransmitter precursors L-dopa and 5-hydroxytryptophan. BH4 deficiency is much rarer than classical phenylketonuria. Dihydropteridine reductase (DHPR) deficiency, an autosomal recessive genetic disorder, is a cause of malignant hyperphenylalaninemia due to BH4 deficiency. When left untreated, DHPR deficiency leads to neurologic deterioration at the age of 4 or 5 months, including psychomotor retardation, tonicity disorders, drowsiness, irritability, abnormal movements, hyperthermia, hypersalivation, and difficulty swallowing. Treatment of DHPR deficiency should be initiated as early as possible with BH4 supplementation and replacement of the neurotransmitter precursors L-dopa and 5-hydroxytryptophan. We report the first case of DHPR deficiency in Korea, a child diagnosed at 9 years of age by genetic testing.

Diagnosis, treatment and gene mutation analysis of the first case with dihydropteridine reductase deficiency in the mainland of China / 中华儿科杂志

<p><b>OBJECTIVE</b>The 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency is the most common type of tetrahydrobiopterin (BH4) deficiency. The reported patients with BH4 deficiency are all PTPS deficient found in the mainland of China previously. The activity of dihydropteridine reductase in BH4 metabolism has been determined for 902 patients with hyperphenylalaninemia in the authors' laboratory since 2003. The purposes of this study were to characterize the first case with DHPR deficiency who was diagnosed in June, 2007, to investigate the clinical manifestation, the differential diagnostic criteria, the effect of treatment as well as gene mutation of DHPR deficiency.</p><p><b>METHODS</b>(1) A male patient presented with poor hand control, seizure, hypotonia and mental retardation since five-month after birth. His phenylalanine (Phe) level was 600 micromol/L and he was diagnosed as hyperphenylalaninemia at the age of one year and six-month. (2) This patient was subjected to combined Phe (100 mg/kg) and BH4 (20 mg/kg) loading test, to evaluate the degree of Phe level response to BH4. Urinary neopterin and biopterin analysis as well as the determination of DHPR activity in dried blood spot were also performed. (3) The blood DNA samples of the patient and his parents were collected to amplify the seven exons of QDPR gene using related primers, and the amplified products were directly sequenced for mutation analysis. (4) The patient was treated with BH4 or with a combined small amount of Phe-free special milk, neurotransmitter precursors and folic acid after the diagnosis and was followed up for clinical effects of treatment.</p><p><b>RESULTS</b>(1) The basic Phe level was 476 micromol/L, then it increased to 1355 micromol/L at 3 h after taking Phe and slowly decreased to 610 micromol/L at 24h after taking BH4. (2) The basic urinary neopterin and biopterin were 2.92 mmol/mol Cr (normally < 2.61 mmol/mol Cr) and 7.44 mmol/molCr (normally < 2.67 mmol/mol Cr) respectively, and biopterin percentage was 71.79% (normally 42.7% - 75.9%). The patient had higher biopterin level. (3) The DHPR activity of this patient was (0.27 - 0.51) nmol/(min.5 mm disc) which were 6.11% - 10.6% of normal control, so he was diagnosed as DHPR deficiency. (4) The analysis of QDPR gene mutation showed that the patient carries missense mutation c.515C > T (P172L) from his father and nonsense mutation c.661C > T (R221X) from his mother. The c.515C > T is not reported before, we also did not find this mutation in 50 normal children. (5) The patient started to be treated with large dosage of BH4 (10 - 20) mg/(kg.d) or BH4 combined with small amounts of Phe-free milk, neurotransmitter precursors L-dopa (3 - 5) mg/(kg.d) plus carbidopa, 5-hydroxytryptophan (3 - 5) mg/(kg.d), and folic acid 15 mg/d as well at the age of one year and six-month after the diagnosis. The seizure has disappeared, the symptoms such as hypotonia have been obviously improved and the Phe level was 60 micromol/L at the six months after the treatment in this patient.</p><p><b>CONCLUSION</b>(1) The patient with DHPR deficiency has common symptoms of BH4 deficiency (such as fair hair, hypotonia, mental retardation), and there is metabolic disturbance of folic acid in DHPR deficiency. (2) The higher Phe levels slowly decreased after BH4 loading test, the urinary biopterin level was very high and the DHPR activity was very low in the patient with DHPR deficiency. (3) The c.515C > T may be a new mutation of QDPR gene. (4) The DHPR deficient patient must be treated with higher dose of BH4 (8 - 20) mg/(kg.d), neurotransmitter precursors and folic acid as well.</p>

Screening for tetrahydrobiopterin metabolic disorders and related gene analysis among the patients with motor disturbance and mental retardation / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To study the incidence of various enzyme deficiency in tetrahydrobiopterin (BH4) metabolism and the related gene mutation among the patients with motor disturbance and mental retardation.</p><p><b>METHODS</b>One hundred patients with unknown motor disturbance and mental retardation were referred to this study. All patients were performed by phenylalanine (Phe) and BH4 loading test, urinary pterin analysis and dihydropteridine reductase (DHPR) activity. Some patients received the dopa treatment for diagnosis of dopa-responsive dystonia (DRD). The analysis of GTP cyclohydrolase 1 gene (GCH1) mutation for DRD patients and the analysis of 6-pyruvoyl tetrahydropterin synthase (PTS) gene mutations for PTS deficient patients were done under the consent from their parents.</p><p><b>RESULTS</b>Seventy of 100 patients had normal basic blood Phe levels, six (6%) patients were diagnosed as DRD. Thirty patients had hyperphenylalaninemia (HPA), eight (8%) were diagnosed as PTS deficiency and 22(22%) were diagnosed as phenylalanine hydroxylase (PAH) deficiency. All patients had normal DHPR activity. The mutation IVS5+3insT of GCH1 was found in 2 patients with DRD. Seven kinds of PTS mutations were found in 8 patients with PTS deficiency, and 75% of the mutations were 259C-->T,286G-->A and 155A-->G.</p><p><b>CONCLUSION</b>Some patients with unknown motor disturbance and mental retardation may suffer from BH4 metabolism related diseases. Theses patients are necessary to be screened for such kind of diseases in order to confirm the diagnosis.</p>

Clinical study of tetrahydrobiopterin responsive phenylalanine hydroxylase deficiency in southern and northern Chinese patients / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze characteristics of different hyperphenylalaninemia (HPA) and to discuss the clinical difference between southern and northern Chinese patients with tetrahydrobiopterin (BH4) responsive phenylalanine hydroxylase (PAH) deficiency.</p><p><b>METHODS</b>(1)BH4 (20 mg/kg) loading test was performed in all 108 HPA patients. These patients, 63 males and 45 females, were at a mean age of 7.05 months. A combined phenylalanine (Phe) and BH4 loading test was carried out in the patients who had a basic blood Phe concentration less than 600 micromol/L. The urine pterine profile analysis and the dihydropteridine reductase (DHPR) activity in dry blood filter spot were analyzed simultaneously. (2)BH4 responsive patients were divided to southern and northern groups by their parent's native place and geographic boundary determined by Changjiang River. The change of Phe concentration after BH4 loading test was compared between the two groups.</p><p><b>RESULTS</b>(1)Among the 108 HPA cases, 36 patients (33.3%) were BH4 responsive PAH deficiency, 49 (45.4%) were non-BH4 no responsive phenylketonuria (PKU)and 23(21.3%)were BH4 deficiency (BH4D). The Phe concentration of patients with BH4 responsive PAH deficiency decreased by 49.24% and 65.35% at 8 h and 24 h after oral BH4, 23 in southern group and 13 in northern group among 36 patients. (2)The mean Phe concentration at 24 h after loading test in southern and northern groups were (217.02+/-189.03) micromol/L and 458.75+/-342.54 micromol/L respectively (P<0.05), although the decrease percent of plasma Phe concentration at 2 h, 4 h, 8 h, 24 h was no distinct difference between southern and northern groups (P>0.05).</p><p><b>CONCLUSION</b>Most of mild and moderate HPA patients affected by PAH deficiency show plasma Phe concentration decrease >30% in 24 h after oral BH4 20 mg/kg, few are classic PKU. The responsiveness to BH4 is no difference between southern and northern Chinese patients with BH4 responsive PAH deficiency according to the decrease percent of plasma Phe concentration, although the Phe concentration is lower in southern patients than that in northern patients.</p>

Study on tetrahydrobiopterin deficiency in Northern Chinese population / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To emphasize early differential diagnosis from patients with hyperphenylalaninemia (HPA) and to evaluate the treatment and long-term outcome of patients with tetrahydrobiopterin synthase (BH4) deficiency in Northern Chinese population.</p><p><b>METHODS</b>From 1992 to 2005, a total of 618 patients with HPA were diagnosed and/or cared for in our outpatient clinic. Urinary pterin analysis, detection of dihydropteridine reductase (DHPR) activity in blood, and then BH4 loading tests were carried out to differentiate BH4 deficiency in these patients from classical phenylketonuria. BH4 deficient patients were treated with BH4, levodopa and 5-hydroxytryptophane (5-HTP) immediately while the diagnosis was done to disease. Patientso blood phenylalanine levels, psychomotor and intelligence development were followed up.</p><p><b>RESULTS</b>A total of 38 cases were diagnosed as BH4 deficiency, all of them were revealed as 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency from the extremely decreased urine biopterin, normal DHPR activities and drop down of blood phenylalanine level to normal range within 4 to 8 hours after BH4 loading. The most common manifestations were progressively psychomotor and mental retardation to patients even after taking early dietary treatment. The patients were diagnosed and treated with drugs at the ages of 2.1 months to 13 years. With 4 patients died of pneumonia, 7 patients refused to treatment, only 27 patients were under treatment and followed up. The average full scale development or intelligence quotient (DQ/IQ) of patients who were treated within and after 6 months were 86+/- 10 or 66+/- 7 respectively. Development was not even in different aspects. A significant negative correlation was observed between the level of the DQ and the age of treatment commenced (r was -0.714, P< 0.01). Eleven patients experienced the extrapyramidal movement disorders, 3 of them combined with epilepsy. The extrapyramidal disorders were controlled by administration of levodopa.</p><p><b>CONCLUSION</b>The differential diagnosis for BH4 deficiency should be carried out in all patients with HPA. PTPS deficiency is the most common form of BH4 deficiency in Northern Chinese population. The long-term outcome of these patients benefits from diagnosis and treatment with BH4, levodopa and 5-HTP as early as possible.</p>

Tetrahydrobiopterin loading test in differential diagnosis among hyperphenylalaninemia patients / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To perform tetrahydrobiopterin (BH(4)) loading test and to further understand its usefulness in differential diagnosis among hyperphenylalaninemia(HPA) patients.</p><p><b>METHODS</b>BH(4) loading test was carried out in 73 HPA patients, including the positive cases unveiled by neonatal screening and the clinically suspected cases. These patients, 47 males and 26 females, were at a mean age of 1.93 months. BH(4) (20 mg/kg) loading test was performed in all patients, and a combined phenylalanine (Phe)(100 mg/kg) and BH(4) loading test was performed among the patient who had a basic blood Phe concentration less than 600 micro mol/L. The urine pterine profile analysis and the dihydropteridine reductase activity in dry blood filter spot were tested simultaneously.</p><p><b>RESULTS</b>During BH(4) loading test or combined Phe and BH(4) loading test, the patients with classic phenylketonuria showed no response to BH(4), the patients with moderate HPA caused by Phe hydroxylase deficiency decreased 32.8% of blood Phe level and the patients with BH(4) deficiency showed a prompt reduction in blood Phe level and it decreased to normal level at 4 h and lasted until 24 h. Twenty-two cases were diagnosed as classic phenylketonuria, 39 were moderate phenylketonuria and 12 were BH(4) deficiency.</p><p><b>CONCLUSION</b>Hyperphenylalaninemia may be caused by deficiency of Phe hydroxylase or by deficiency of co-factor BH(4). Early diagnosis is important. BH(4) loading test is a safe and fast test in vivo. It is sensitive, easy-to-do, and is highly useful in differential diagnosis for suspected cases of HPA.</p>

Urinary neopterin and dihydropteridin reductase in children with rheumatoid arthritis

To evaluate the role of pteridin pathway in juvenile rheumatoid arthritis [JRA] urinary neopterin, dihydropterin reductase activity [DHPR] together with serum creatinine and C reactive protein was estimated in 20 children with JRA during activity [GI] and 20 children with JRA during remission [GII] compared with 15 healthy children [GIII]. Neopterin excretion was significantly increased in GI with active RA [608.25 +/- 181.2] than GII with RA during remission [137.6 +/- 33] and GIII [79.2 +/- 26.79]. No statistical correlation was found between urinary neopterin excretion and DHPR in the studied groups