Clinical, Biochemical, and Genetic Findings of Cystinuria in Chinese Children.

BACKGROUND: Cystinuria is a rare inherited renal stone disease caused by mutations in the SLC3A1 and SLC7A9 genes. The Chinese cystinuria phenotype and genotype have rarely been reported in the literature. METHODS: For this research, the clinical features and genetic etiology were analyzed in seven children, and the clinical characteristics were summarized. The blood and urine amino acids and acylcarnitine were analyzed. Additionally, the whole coding sequence and exon-intron junctions of the SLC3A1 and SLC7A9 genes were analyzed. RESULTS: These seven patients with cystinuria were from seven unrelated Chinese families, and they were diagnosed between the ages of 1 month and 16 years old. The urinary amino acids, including ornithine, arginine, and threonine, were elevated in these patients. A homozygous c.325G>A mutation in SLC7A9 was identified in two patients, and six SLC3A1 mutations were found in five patients. CONCLUSIONS: The core pedigree analysis showed that most of the parents carried mutations; however, there was no association between the clinical course and the genotype.

[Reye syndrome and sudden death symptoms after oral administration of nimesulide due to upper respiratory tract infection in a boy].

A boy aged 6 years and 3 months developed upper respiratory tract infection and pyrexia 2 months ago and was given oral administration of nimesulide by his parents according to directions. Half an hour later, the boy experienced convulsions and cardiopulmonary arrest, and emergency examination found hypoketotic hypoglycemia, metabolic acidosis, significant increases in serum aminotransferases and creatine kinase, and renal damage. Recovery of consciousness and vital signs was achieved after cardiopulmonary resuscitation, but severe mental and movement regression was observed. The boy had a significant reduction in free carnitine in blood and significant increases in medium- and long-chain fatty acyl carnitine, urinary glutaric acid, 3-hydroxy glutaric acid, isovalerylglycine, and ethylmalonic acid, suggesting the possibility of multiple acyl-CoA dehydrogenase deficiency. After the treatment with vitamin B2, L-carnitine, and bezafibrate, the boy gradually improved, and reexamination after 3 months showed normal biochemical parameters. The boy had compound heterozygous mutations in the ETFDH gene, i.e., a known mutation, c.341G>A (p.R114H), from his mother and a novel mutation, c.1484C>G (p.P495R), from his father. Finally, he was diagnosed with multiple acyl-CoA dehydrogenase deficiency. Reye syndrome and sudden death symptoms were caused by nimesulide-induced acute metabolic crisis. It is concluded that inherited metabolic diseases may be main causes of Reye syndrome and sudden death, and biochemical and genetic analyses are the key to identifying underlying diseases.

Treatment with Isorhamnetin Protects the Brain Against Ischemic Injury in Mice.

Ischemic stroke is a major cause of morbidity and mortality, yet lacks effective neuroprotective treatments. The aim of this work was to investigate whether treatment with isorhamnetin protected the brain against ischemic injury in mice. Experimental stroke mice underwent the filament model of middle cerebral artery occlusion with reperfusion. Treatment with isorhamnetin or vehicle was initiated immediately at the onset of reperfusion. It was found that treatment of experimental stroke mice with isorhamnetin reduced infarct volume and caspase-3 activity (a biomarker of apoptosis), and improved neurological function recovery. Treatment of experimental stroke mice with isorhamnetin attenuated cerebral edema, improved blood-brain barrier function, and upregulated gene expression of tight junction proteins including occludin, ZO-1, and claudin-5. Treatment of experimental stroke mice with isorhamnetin activated Nrf2/HO-1, suppressed iNOS/NO, and led to reduced formation of MDA and 3-NT in ipsilateral cortex. In addition, treatment of experimental stroke mice with isorhamnetin suppressed activity of MPO (a biomarker of neutrophil infiltration) and reduced protein levels of IL-1ß, IL-6, and TNF-α in ipsilateral cortex. Furthermore, it was found that treatment of experimental stroke mice with isorhamnetin reduced mRNA and protein expression of NMDA receptor subunit NR1 in ipsilateral cortex. In conclusion, treatment with isorhamnetin protected the brain against ischemic injury in mice. Isorhamnetin could thus be envisaged as a countermeasure for ischemic stroke but remains to be tested in humans.

[Limb torsion and developmental regression for one month after hand, foot and mouth disease in an infant].

A one-year-old girl visited the hospital due to limb torsion and developmental regression for one month after hand, foot and mouth disease. At the age of 11 months, she visited a local hospital due to fever for 5 days and skin rash with frequent convulsions for 2 days and was diagnosed with severe hand, foot and mouth disease, viral encephalitis, and status epilepticus. Brain MRI revealed symmetric abnormal signals in the bilateral basal ganglia, bilateral thalamus, cerebral peduncle, bilateral cortex, and hippocampus. She was given immunoglobulin, antiviral drugs, and anticonvulsant drugs for 2 weeks, and the effect was poor. Blood and urine screening for inherited metabolic diseases were performed to clarify the etiology. The analysis of urine organic acids showed significant increases in glutaric acid and 3-hydroxyglutaric acid, which suggested glutaric aciduria type 1, but her blood glutarylcarnitine was normal, and free carnitine significantly decreased. After the treatment with low-lysine diets, L-carnitine, and baclofen for 1 month, the patient showed a significant improvement in symptoms. Hand, foot and mouth disease is a common viral infectious disease in children, and children with underlying diseases such as inherited metabolic diseases and immunodeficiency may experience serious complications. For children with hand, foot and mouth disease and unexplained encephalopathy, inherited metabolic diseases should be considered.

[Psychomotor retardation and intermitent convulsions for 8 months in an infant].

This study reports a boy with psychomotor retardation and epilepsy due to maternal phenylketonuria (PKU). The boy was admitted at the age of 20 months because of psychomotor retardation and epilepsy. He had seizures from the age of 1 year. His development quotient was 43. He presented with microcephaly, normal skin and hair color. Brain MRI scan showed mild cerebral white matter demyelination, broadening bilateral lateral ventricle and foramen magnum stricture. Chromosome karyotype, urine organic acids, blood amino acids and acylcarnitines were normal. His mother had mental retardation from her childhood. She presented with learning difficulties and yellow hair. Her premarriage health examinations were normal. She married a healthy man at age of 26 years. When she visited us at 28 years old, PKU was found by markedly elevated blood phenylalanine (916.54 µmol/L vs normal range 20-120 µmol/L). On her phenylalanine hydroxylase (PAH) gene, a homozygous mutations c.611A>G (p.Y204C) was identified, which confirmed the diagnosis of PAH-deficient PKU. Her child carries a heterozygous mutation c.611A>G with normal blood phenylalanine. Her husband had no any mutation on PAH. It is concluded that family investigation is very important for the etiological diagnosis of the children with mental retardation and epilepsy. Carefully clinical and metabolic survey should be performed for the parents with mental problems to identify parental diseases-associated child brain damage, such as maternal PKU.

[Acute brainstem encephalitis and myelitis in a girl with isolated methylmalonic aciduria due to MUT gene defect].

Methylmalonyl CoA mutase deficiency due to MUT gene defect has been known as the main cause of isolated methylmalonic acidemia in Mainland China. This study reported a patient with isolated methylmalonic aciduria (MUT type) characterized as acute brainstem encephalitis and myelitis. The previously healthy girl presented with fever, lethargy and progressive weakness in her extremities at the age of 3 years and 2 months. Three day later, she had respiratory distress and consciousness. Cranial MRI revealed bilateral symmetrical lesion of pallidum, brain stem and spinal cord, indicating acute brainstem encephalitis and myelitis. Her blood propionylcarnitine (6.83 µmol/L vs normal range 1.0 to 5.0 µmol/L) and urinary methylmalonic acid (133.22 mmol/mol creatinine vs normal range 0.2 to 3.6 mmol/mol creatinine) increased significantly. Plasma total homocysteine was normal. On her MUT gene, a reported mutation (c.1630_1631GG>TA) and a novel mutation (c.1663C>T, p.A555T) were identified, which confirmed the diagnosis of methylmalonic aciduria (MUT type). After cobalamin injection, protein-restricted diet with the supplements of special formula and L-carnitine, progressive improvement has been observed. The clinical manifestation of patients with methylmalonic aciduria is complex. Metabolic study and gene analysis are keys for the diagnosis and treatment of the disorder.

[A Chinese boy with methylmalonic aciduria cblB type and a novel mutation in the MMAB gene].

cblB defect is a rare type of methylmalonic aciduria. In this study, a Chinese boy was diagnosed with methylmalonic aciduria cblB type and a novel mutation in the MMAB gene. The clinical presentations, blood acylcarnitines profiles, urine organic acids and genetic features of the patient were reported. The boy presented with fever, feeding difficulty and lethargy at the age of 2 months. Seven days later, he had coma, cold limb, thrombocytopenia, metabolic acidosis and liver damage. His blood propionylcarnitine and urinary methylmalonic acid levels increased significantly, but the plasma total homocysteine level was in the normal range, which supported the diagnosis of isolated methylmalonic aciduria. Gene analysis was performed by direct sequencing. No mutation in the MUT gene was found. However, a reported mutation c.577G>A (p.E193K) and a novel mutation c.562G>A (p.V188M) in the MMAB gene were identified, which confirmed the diagnosis of methylmalonic aciduria cblB type. Progressive clinical and biochemical improvement has been observed after hydroxylcobalamin injection, protein-restricted diet with the supplements of special formula and L-carnitine. He is currently 3 years and 11 months old and has a normal development condition. The phenotypes of the patients with cblB defect are nonspecific. Metabolic analysis and MMAB gene analysis are keys for the diagnosis of the disorder.

[Clinical and ATP7A gene analysis of three infants with Menkes disease and prenatal diagnosis for a fetus at risk].

Menkes disease is a rare X-linked recessive disorder characterized by multi-systemic disorder of copper deficiency caused by ATP7A gene mutation. In this study, the clinical and laboratory features of three patients with Menkes disease were analyzed. Prenatal diagnosis had been performed for a fetus of a family. Three patients were admitted at the age of 8-9 months due to severe epilepsies and marked delayed psychomotor development. Significantly light complexion, pudgy cheeks and sparse fuzzy wooly hair were observed. On their cranial MR imaging, cortical atrophy, leukoencephalopathy, basal ganglia damage and tormesity of the intracranial vessels were found. Their plasma ceruloplasmin decreased to 70.2, 73.5 and 81 mg/L, significantly lower than normal range (210-530 mg/L). c.3914A>G (p. D1305G) was detected on ATP7A gene of case 1 and 2. A novel mutation, c.3265G>T (p.G1089X) was found in case 3. Both of them were firstly found in Chinese patients of Menkes disease. The mother of case 1 was tested at 20 weeks of pregnancy. Karyotype and ATP7A gene studies of the amniocytes were performed for the prenatal diagnosis of her fetus. Normal male karyotypes without c.3914A>G mutation on ATP7A gene was showed. Postnatal genetic analysis and normal development confirmed the prenatal diagnosis.

[Methylenetetrahydrofolate reductase deficiency-induced schizophrenia in a school-age boy].

Methylenetetrahydrofolate reductase (MTHFR) deficiency is a rare autosomal recessive disorder. It is known that MTHFR deficiency may result in hyperhomocysteinemia, but MTHFR deficiency-induced schizophrenia has been rarely reported. Here we present the clinical course, biochemical and genetic characteristics of schizophrenia resulted from MTHFR deficiency in a school-age boy. He was 13 years old. He was admitted with a two-year history of fear, auditory hallucination, learning difficulty, sleeping problems, irascibility, drowsing and giggling. At admission, he had significantly elevated plasma and urine levels of total homocysteine, significantly decreased levels of folate in serum and cerebrospinal fluid, and a normal blood concentration of methionine. Further DNA sequencing analysis showed 665C>T homozygous mutations in the MTHFR gene. The patient was diagnosed with MTHFR deficiency-associated schizophrenia and treatment with calcium folinate, vitamin B12, vitamin B6, and betaine was initiated. After the treatment for 1 week, his plasma and urine levels of homocysteine were decreased to a normal range and the clinical symptoms were significantly improved. After 3 months of treatment, the patient returned to school. He is now living with normal school life. In summary, children with late-onset MTHFR deficiency and secondary cerebral folate deficiency may lead to schizophrenia. This rare condition can be early diagnosed through analyses of blood and urine total homocysteine, amino acids in blood and folate in blood and cerebral fluid and successfully treated with folinic acid, vitamin B6, vitamin B12 and betaine.

[A boy with Fabry disease with the onset at the age of four].

Fabry disease is an X-linked recessive lysosomal storage disorder caused by a deficiency of α-galactosidase A (GLA). Intracellular accumulation of globotriaosylceramide, the glycolipid substrate of this enzyme, leads to severe painful neuropathy with progressive renal, cardiovascular, and cerebrovascular dysfunction. Patients of severe cases die young. It has been proved that enzyme replacement therapy is a useful method to treat patients with Fabry disease. But the clinical diagnosis of the patients may often be difficult because of the lack of specific symptoms. In this study, a Chinese boy was diagnosed as Fabry disease at the age of 11 years with episodic pain for 7 years. The boy described the onset, at the age of 4 years, of episodic burning pain in the toes. Generalized aching and pain in the feet became progressive in the past two years and his hands were also affected. Divers analgesics were tried without effects. When he was admitted at the age of 11 years, none of complications was found in his heart, brain, kidneys, skin and eyes by routine laboratory examinations. Significantly decreased GLA activity of peripheral leucocytes [1.0 nmol/(h×mg protein) vs. normal control 24.5 to 86.1 nmol/(h×mg protein)] supported the diagnosis of Fabry disease. A splicing mutation IVS6+2 T>C was identified on his GLA gene. But it was not found in his mother and younger sister. The incidence of Fabry disease is not clear in Mainland China. The patients usually have insidious onset with complex and non-specific clinical manifestations. Stroke, uremia, cardiomyopathy and multiple organ dysfunctions are common at the late stage. Early diagnosis is the key point to reduce the mortality and handicap. GLA enzyme activity is important to the diagnosis of Fabry disease. The mutation analysis of GLA gene is helpful for genetic counseling.

Case report: An asymptomatic mother with an inborn error of cobalamin metabolism (cblC) detected through high homocysteine levels during prenatal diagnosis.

Background: The most common disorder of the intracellular cobalamin metabolism pathway is the combined methylmalonic acidemia and homocysteinemia, cblC type (cblC). There is a variation in its clinical spectrum ranging from severe neonatal-onset forms that are highly fatal to later-onset forms which are milder. In this study, the first case of an asymptomatic Chinese woman with a defect in congenital cobalamin (cblC type) metabolism at prenatal diagnosis due to elevated homocysteine level is identified. Case presentation: The proband, a male child born to a 29-year-old G1P0 mother, admitted to local hospital with feeding disorder, intellectual disability, seizures, microcephaly, as well as heterophthalmos. The level of the urine methylmalonic was elevated. Equally found were increased blood propionylcarnitine (C3) and propionylcarnitine/free carnitine ratio (C3/C0) and decreased methionine levels. The plasma total homocysteine level was elevated at 101.04 µmol/L (normal < 15 µmol/L). The clinical diagnosis of combined methylmalonic acidemia and homocysteinemia was supported. Four years later, the mother of the boy married again and came to us for prenatal diagnosis exactly 15 weeks after her last menstrual period. Subsequently, there is an increase in the amniotic fluid methylmalonate. The level of the amniotic fluid total homocysteine was marginally high. A considerably elevated amniotic fluid C3 was equally observed. In addition, there is a respective significant increase in the plasma and urine total homocysteine at 31.96 and 39.35 µmol/L. After the sequencing of MMACHC genes, it is found that the boy, a proband carried a homozygous mutation of the MMACHC at c.658_660delAAG. While the boy's mother, she carries two mutations in MMACHC: c.658_660delAAG and c.617G>A. The fetus is a carrier of the MMACHC gene. Following the administration of routine treatment, the mother remained symptom-free in the course of pregnancy, and she gave birth to a healthy boy. Conclusion: Variable and nonspecific symptoms characterized the cblC type of methylmalonic acidemia combined with homocysteinemia. Both biochemical assays and mutation analysis are recommended as crucial complementary techniques.

[Intrahepatic cholestasis due to mitochondrial respiratory chain complex I deficiency in a Chinese boy].

Mitochondrial respiratory chain deficiency is a common cause of mitochondrial disease in children. This study aimed to review the clinical, enzymatic and genetic characteristics of a Chinese boy with progressive intrahepatic cholestasis due to mitochondrial respiratory chain complex I deficiency. The boy developed diarrhea from the age of 13 months, followed by progressive body weight loss, jaundice and weakness. His urine organic acids, blood amino acids and acylcarnitines profiles were normal. Mitochondrial respiratory chain complexes I to V activities in peripheral leukocytes were measured using spectrophotometric assay. Complex I activity was reduced. 5821G>A mutation was indentified by gene sequencing on tRNA-cys of mitochondrial gene in the patient and his mother. Vitamin supplements, liver protection, antibiotics and plasma infusion were not effective in the patient. Unfortunately, the boy died at the age of 17 months. Mitochondrial respiratory chain complex I deficiency is the most common mitochondrial respiratory chain disorder. This was the first case of intrahepatic cholestasis due to complex I deficiency confirmed by mitochondrial respiratory chain enzyme activity assay and gene analysis in China. It was concluded that mitochondrial hepatopathy is one of major causes of metabolic hepatopathy. Biochemical assay, mitochondrial respiratory chain complex activities assay and genetic analysis are crucial for the etiological diagnosis of metabolic hepatopathy.

[Mitochondrial respiratory chain complex I deficiency due to 10191T>C mutation in ND3 gene].

This study reviews a case of mitochondrial respiratory chain complex I deficiency due to the 10191T>C mutation in mitochondrial ND3 gene. The previously healthy boy progressively presented with blepharoptosis, weakness, epilepsy and motor regression at age 6 years. Elevated blood lactate and pyruvate were observed. Brain magnetic resonance imaging showed symmetrical lesions in the basal ganglia. Leigh syndrome was thus confirmed. The protein from the mitochondria and genomic DNA of the boy and his parents was collected from peripheral blood leucocytes for the activity test for mitochondrial complex I to V and genetic analysis. The results showed the activity of complex I (33.1 nmol /min in 1 milligram mitochondrial protein) was lower than normal reference value (44.0±5.4 nmol /min in 1 milligram mitochondrial protein). The ratio of complex I to citrate synthase (19.8%) was also lower than normal reference value (48%±11%). The activities of complexes II to V were normal. 10191T>C mutation in ND3 gene of mitochondria was identified in the boy. 10191T>C mutation and complex I deficiency were not detected in his parents. At present, he is 16 years old, and of normal intelligence with spastic paralysis in both lower extremities after treatment. It is concluded that a Chinese boy with isolated complex I deficiency due to 10191T>C mutation in ND3 gene was firstly diagnosed by peripheral leukocytes mitochondrial respiratory chain enzyme assay and gene analysis. This study can provide clinical data for the nosogenesis of Leigh syndrome.

[Leucodystrophy induced by late onset 3-hydroxy-3-methylglutaric aciduria].

3-Hydroxy-3-methylglutaric aciduria is a rare disorder of organic acid metabolism caused by 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency. The disorder was common in neonatal or infant period. Here a case of late onset 3-hydroxy-3-methylglutaric aciduria complicated by leucodystrophy was reported. The patient was a 7-year-old boy. He presented with progressive headache, drowsiness and vomiting. Hepatic lesions, ketosis and leucopenia were found. Symmetrical diffused leucodystrophy was shown by MRI. Blood levels of isovalerylcarnitine and acetylcarnitine increased significantly. Urinary levels of 3-hydroxy-3-methylglutaric, 3-methylglutaconic, 3-hydroxyglutaric acids and 3-methyl-crotonylglycine increased significantly. Symptoms were released by intravenous infusion of L-carnitine and glucose. After treatment for 6 months, urinary levels of 3-hydroxy-3-methylglutaric aciduria decreased in the boy and his health improved.

[Leigh syndrome due to mitochondrial respiratory chain complex II deficiency].

Mitochondrial respiratory chain complex II deficiency is a rare documented cause of mitochondrial diseases. This study reported a case of Leigh syndrome due to isolated complex II deficiency. A boy presented with progressive weakness, motor regression and dysphagia after fever from the age of 8 months and hospitalized at the age of 10 months. Elevated blood levels of lactate and pyruvate were observed. Brain magnetic resonance image showed symmetrical lesions in the basal ganglia. Mitochondrial respiratory chain complex I-V activities in peripheral leukocytes were measured using spectrophotometric assay. Mitochondrial gene screening of common point mutations was performed. The complex II activity in the peripheral leukocytes decreased to 21.9 nmol/min per mg mitochondrial protein (control: 47.3±5.3 nmol/min per mg mitochondrial protein). The ratio of complex II activity to citrate synthase activity (22.1%) also decreased (control: 50.9%±10.7 %). No point mutation was found in mitochondrial DNA. The boy was diagnosed as Leigh syndrome due to isolated complex II deficiency. Psychomotor improvements were observed after the treatment. The patient is 22 months old and in a stable condition.

Prenatal diagnosis of methylmalonic aciduria by analysis of organic acids and total homocysteine in amniotic fluid.

BACKGROUND: Methylmalonic aciduria (MMA) is the most frequent disease of organic aciduria in China. Various biochemical strategies are followed for the prenatal diagnosis of MMA. However, since fetuses affected by MMA have decreased excretion of methylmalonic acid, the difficulties of prenatal biochemical diagnosis are obvious. Gas chromatography mass spectrometry (GC/MS) and tandem mass spectrometry (ESI/MS/MS) have allowed us to identify the disease in affected fetuses. The aim of this study was to determine the value of analysis of organic acids and total homocysteine in amniotic fluid in prenatal diagnosis of MMA. METHODS: The clinical diagnoses and outcomes of nine probands with MMA and the prenatal diagnoses based on biochemical analysis of nine fetuses at risk for MMA were investigated. Amniotic fluid samples from pregnancies at risk for MMA and metabolically normal pregnancies were obtained at 16 - 24 weeks of gestation. Methylmalonic acid and methylcitric acid were measured by GC/MS, propionylcarnitine was analyzed by ESI/MS/MS, and total homocysteine was determined by fluorescence polarization immunoassay. RESULTS: In two pregnancies, high levels of methylmalonic acid, methylcitric acid, propionylcarnitine, and total homocysteine indicated combined MMA and homocysteinemia in the fetuses. One of the mothers continued pregnancy and received cobalamin supplement as prenatal treatment, and the other terminated her pregnancy. In one pregnancy, significantly elevated levels of methylmalonic acid, methylcitric acid, and propionylcarnitine, and normal level of total homocysteine was found indicating isolated MMA in the fetus; abortion was performed on this case. In the other six pregnancies, all the levels of the above mentioned metabolites were normal suggesting that the fetuses were not affected by MMA. The diagnoses were confirmed after delivery by testing urinary organic acids and plasma total homocysteine. CONCLUSIONS: The metabolic abnormalities of MMA occur early in gestation. The level of total homocysteine in amniotic fluid may be an additional indicator of fetal combined MMA and homocysteinemia. Determination of total homocysteine level in amniotic fluid may become a convenient and reliable method for prenatal diagnosis of the disease.

Eight novel mutations of CBS gene in nine Chinese patients with classical homocystinuria.

BACKGROUND: Classical homocystinuria (homocysteinemia type 1, MIM# 236200) is a rare inherited disorder in Mainland China. This study aimed to identify mutations in the cystathionine ß-synthase (CBS) gene which are associated with classical homocystinuria in nine Chinese patients. METHODS: Nine Chinese patients were diagnosed at the age of 5 years 4 months to 18 years by plasma total homocysteine and blood methionine determination. CBS gene analysis was performed for the patients and their families. RESULTS: All nine patients had significantly increased plasma total homocysteine (142-500 µmol/L vs. the normal range of 0-15 µmol/L) and blood methionine (144.3-500 µmol/L vs. the normal range of 0-50 µmol/L). None of the patients was pyridoxine responsive. Eleven mutations in CBS gene were identified in the nine patients. Eight mutations (IVS3+1G>A, p.Thr493fsX46, p.Thr236Asn, p.Leu230Gln, p.Lys72Ile, p.Ser201ProfsX36, p.Met337IlefsX115, and IVS14-1G>C) were novel. Three mutations (p.Arg125Gln, p.Thr257Met and p.Gly116Arg) had been previously reported. CONCLUSIONS: In this study, eight novel mutations in CBS were identified in nine Chinese patients with classical homocystinuria. None of the hotspot mutations reported in other regions previously was found. These data indicated that Chinese maybe had different CBS mutation spectrum from other population. The identification of mutations not only confirms the diagnosis but also enables accurate genetic counselling and prenatal diagnosis for the fetuses of the families.

Prenatal diagnosis of citrullinemia type 1: a Chinese family with a novel mutation of the ASS1 gene.

BACKGROUND: Argininosuccinate synthetase deficiency (citrullinemia type 1) is a rare autosomal recessive disorder of the urea cycle characterized by elevated concentrations of citrulline, ammonia, and orotic acid, manifesting with acute hyperammonemic crises, usually early in life, with concurrent neurologic deterioration. Only a few cases of citrullinemia type 1 have been documented from mainland China. Prenatal diagnosis has not been performed. METHODS: A Chinese family affected by citrullinemia type 1 was studied. The proband, a girl, was the second child born to a non-consanguineous couple. Her elder brother died at 19months due to coma and liver dysfunction of unknown cause. The proband was admitted because of severe mental retardation and lethargy at the age of 15months. Initial laboratory results revealed hyperammonaemia, hypercitrullinemia (928.771µmol/L, normal 5.0-25.0µmol/L) and orotic aciduria, supporting the diagnosis of citrullinemia type 1. Subsequently, the mother presented at 15weeks of pregnancy seeking for genetic counseling and prenatal diagnosis. ASS1 gene in the blood leukocytes of the family members and amniocytes was performed by direct sequencing. RESULTS: On the ASS1 gene of the proband, a novel mutation, T1009C (C337R), and a previously reported mutation G847A (E283K) were identified. Each parent carries one of two mutations. G847A and T1009C mutations were detected in amniocytes, as same as the proband of the family. The result revealed that the fetus was affected by argininosuccinate synthetase deficiency. The parents chose to have a termination of the pregnancy. CONCLUSIONS: Prenatal diagnosis for citrullinemia type 1 was performed in a Chinese family using gene analysis. T1009C (C337R), a novel mutation of ASS1, was identified.

Two compound frame-shift mutations in succinate dehydrogenase gene of a Chinese boy with encephalopathy.

OBJECTIVE: To investigate respiratory chain complex II deficiency resulted from mutation in succinate dehydrogenase gene (SDH) encoding complex II subunits in China. METHODS: An 11-year-old boy was admitted to our hospital. He had a history of progressive psychomotor regression and weakness since the age of 4years. His cranial magnetic resonance imaging revealed focal, bilaterally symmetrical lesions in the basal ganglia and thalamus, indicating mitochondrial encephalopathy. The activities of mitochondrial respiratory chain enzymes I-V in peripheral leukocytes were determined via spectrophotometry. Mitochondrial DNA and the succinate dehydrogenase A (SDHA) gene were analyzed by direct sequencing. RESULTS: Complex II activity in the leukocytes had decreased to 33.07nmol/min/mg mitochondrial protein (normal control 71.8±12.9); the activities of complexes I, III, IV and V were normal. The entire sequence of the mitochondrial DNA was normal. The SDHA gene showed two heterozygous frame-shift mutations: c.G117G/del in exon 2 and c.T220T/insT in exon 3, which resulted in stop codons at residues 56 and 81, respectively. CONCLUSIONS: We have described the first Chinese case of mitochondrial respiratory chain complex II deficiency, which was diagnosed using enzyme assays and gene analysis. Two novel, compound, frame-shift mutations, c.G117G/del in exon 2 and c.T220T/insT in exon 3 of the SDHA gene, were found in our patient.