Tso-Ren Wang

Neonatal hepatitis: a follow-up study

Fifty-six patients with moderate to severe neonatal hepatitis were followed for 12 to 78 months. Two died from causes other than hepatitis itself and were free from liver disease at the time of death. Of the remaining 54 patients, seven died of hepatitis, two are living with chronic liver disease and psychomotor retardation, and 45 are living without liver disease. High peak bilirubin levels and liver histologic findings of periportal fibrosis, moderate to severe portal inflammation, and/or diffuse giant cell transformation appear to be major factors predictive for poor outcome. Cytomegalovirus (CMV) infection was a common associated infection. Evidence of CMV infection was found in 22 (49%) of the 45 patients studied. Three of them died, and one is still living with cirrhosis of the liver. Metabolic disorders such as alpha-1-antitrypsin deficiency, galaclosemia, and aminoaciduria and/or aminoacidemia were carefully screened but were not found in these cases. A fatal case had a sibling who had died of a similar disease course. Chinese infants may have metabolic and familial cholestasis diseases requiring further investigation.

Neonatal type of nonketotic hyperglycinemia

Two infants with the neonatal type of nonketotic hyperglycinemia that had manifested as early neonatal consciousness disturbance are presented. Transient hyperammonemia had been detected in both initially. High levels of glycine in plasma and cerebrospinal fluid disturb the nervous system, causing variable manifestations of this disease. Both cases were complicated by intracranial hemorrhage, which has never before been reported. After treatment with sodium benzoate and dextromethorphan, some neurologic improvement was observed, although the glycine levels did not lower. Recent clinical trials are reviewed, and because of the unfavorable outcomes, the special need for prenatal diagnosis is highlighted.

Duplication of proteolipid protein gene: A possible major cause of Pelizaeus-Merzbacher disease

The classic form of Pelizaeus-Merzbacher disease is a rare X-linked dysmyelinating disorder of the central nervous system in which mutations of the proteolipid protein gene have been reported since 1989. However, mutations in the proteolipid protein gene have been identified in only 10 to 25% of all cases of Pelizaeus-Merzbacher disease, which suggests that other genetic aberrations may be present. Recently, proteolipid protein gene overdosage was discovered to cause Pelizaeus-Merzbacher disease. By using comparative multiplex polymerase chain reaction and restriction fragment length polymorphism analysis, we confirmed the proteolipid protein gene duplication as the cause of Pelizaeus-Merzbacher disease in 4 patients from 3 Chinese families with Pelizaeus-Merzbacher disease with no detectable exonic mutations. These results support the hypothesis that proteolipid protein gene duplication may be a major cause of Pelizaeus-Merzbacher disease in all ethnic groups and also suggest that the molecular diagnosis of Pelizaeus-Merzbacher disease should therefore include duplication analysis of proteolipid protein gene.

Angelman syndrome assessed by neurological and molecular cytogenetic investigations

Angelman syndrome (AS) is characterized by severe psychomotor retardation, speech impairment, happy disposition with bursts of laughter, ataxia, convulsions, and some distinct physical anomalies. Correct diagnosis of AS is important because of its clinical implications, and once the disease is confirmed, familial genetic counseling becomes crucial. We evaluated 22 patients with a putative diagnosis of AS by both clinical and molecular cytogenetic analysis. A deletion of the region 15q11-13 could be identified cytogenetically in 11 cases by high-resolution technique (group I). Four additional cases were confirmed by fluorescence in situ hybridization (FISH) study with D15S11, SNRPN, D15S10, and GABRB 3 [Prader-Willi syndrome (PWS)/AS region probes] (group II). The common deletion of GABRB 3 was documented in those AS cases (n = 15) by FISH. The other 7 cases exhibited no deletion over 15q11-13 at either the cytogenetic or molecular level (group III). We compared the following associated neurological disorders: convulsions and abnormal EEG, microcephaly, sleep and behavior problems, brain anomalies proved by image studies, sexual precocity with pineal tumor among the three groups, as well as other clinical conditions including congenital heart disease, obesity, scoliosis, and hypopigmentation. In the present study, the differences in neurological and facial characteristics were not distinct among these groups. However, the associated conditions were more frequently observed in the patients with deletion than in those without deletion. The EEG features of AS appear to be less sufficient in helping identify patients at an early age before the clinical features become obvious. Therefore, a region involved in the major As phenotypes may contain only one or more tightly contiguous genes around the GABRB 3 locus, which may explain the clinical heterogeneity in AS.

Treatment and outcome of Taiwanese patients with 6-pyruvoyltetrahydropterin synthase gene mutations

Ten cases of tetrahydrobiopterin (BH4) deficiency were identified in 1,337,490 newborns screened in a Chinese population in Taiwan. The high incidence of BH4 deficiency in the Taiwanese population may be explained by a founder effect, since all of the patients revealed 6-pyruvoyltetrahydropterin synthase gene mutations, and grouping N52S and P87S mutations together constituted 88.9% of the disease alleles. BH4 supplementation with restriction of high-protein foods gave control of plasma phenylalanine within normal range, and levadopa itself prevented seizure. However, the average intelligence quotient (IQ) score of these patients was only 76 ± 14 (56–98). Statistically, the age of starting medication, including 5-hydroxytrytophan (5-HTP), was inversely correlated to IQ scores of these patients. We suggest the combination of BH4, levodopa and 5-HTP as the standard protocol to commence the treatment of BH4 deficiency as early as possible, although prenatal brain damage could have existed.

Identification and characterization of -3c-g acceptor splice site mutation in human α-L-iduronidase associated with mucopolysaccharidosis type IH/S

DNA screening for mutations in the α‐ l‐iduronidase (IDUA) gene was performed in a Chinese mucopolysaccharidosis type IH/S patient. The patient had two different mutations: the maternal allele has L346R (t–g transversion in codon 346) and the paternal allele has 388‐3c–g (c–g transversion at position ‐3 of the 3′ splice site of intron 2). In transfected COS‐7 cells, L346R showed no appreciable IDUA activity (0.4% of normal activity), although it did not cause an apparent reduction in IDUA mRNA or protein level. The 388‐3c–g mutation profoundly affects normal splicing leading to a very unstable mRNA. Expression of the IDUA cDNA containing the mutated acceptor splice site showed trace amounts of enzyme activity (1.6% of normal activity). The results provide further support for the importance of cytosine at the ‐3 position in RNA processing.

Homocystinuria presenting as fatal common carotid artery occlusion

A patient with homocystinuria presenting with fatal cerebral infarction that resulted from left common carotid artery occlusion is reported. This 13-year-old, healthy and intelligent girl presented with progressive cerebral infarction. Angiography revealed total occlusion of the left common carotid artery and stenosis of the right common carotid artery. Distal stenosis of bilateral vertebral arteries was also observed. Initially Takayasu arteritis with unusual manifestation was considered. However, later investigations revealed homocystinuria was the underlying cause. The sudden onset of fatal stroke as the initial clinical presentation of homocystinuria, as observed in this previous healthy teenager, is noteworthy. We suggest metabolic screening for homocystinuria when treating a patient with unusual vascular lesions.

Metabolic function and liver histopathology in Reye-like illnesses

Forty children with Reye syndrome (RS) or Reye‐like illnesses were investigated to elucidate the underlying aetiologies. Extensive biochemical studies including patterns of organic acids and amino acids, liver histopathology, and, if available, a DNA approach were performed. In addition to classical RS (n= 10), the causes of Reye‐like conditions included hereditary organic acidaemias (n= 13), urea cycle defects (n= 4), mitochondrial disorders (n= 3), fulminant hepatitis (n= 2), tyrosinaemia (n= 1), valproate‐associated hepatotoxicity (n= 1), and other non‐specific generalized organic acid disorders (n= 6). It is important to collect specimens when encephalopathy with liver dysfunction of unknown causes is noted. When the underlying inherited metabolic disorders are confirmed, the prevention of the recurrence by adequate diet control and medications, and genetic counselling become possible.

Allele distribution at the FMR1 locus in the general Chinese population

Fragile X syndrome is an important disease of hereditary mental retardation. Its prevalence in the Chinese population is not clear. We amplified FMR1 CGG repeats from male newborns’ blood spots. Approximately 45% of the males had 28 CGG repeats and another 19% had 29 repeats. Besides this major peak, there was a second peak at 34 and 35 repeats. From the 1000 males studied, 3 were found to have repeat numbers in the high borderline range (each with 50, 52 and 53 repeats). This result provides a low but significant risk of fragile X syndrome in the Chinese population.

Molecular cytogenetic studies of duplication 9q32→q34.3 inserted into 9q13

Fluorescence in situ hybridization (FISH) studies using whole chromosome 9 painting probe, classical satellite (9q12‐specific) probe and abl cosmid probe (locus: 9q34) were performed on a female infant who was born with multiple congenital anomalies and the karyotype 46,XX, 9q+. The results of FISH confirm the euchromatic nature of the extra material on the long arm of chromosome 9, and provide evidence that it is of chromosome 9 origin. The structural rearrangement has probably resulted from an insertion of a duplicated segment 9q32→q34.3 into band q13, as shown by the abl cosmid probe. The clinical features in this patient are similar to the previously reported cases of partial trisomy 9q3.