Clinical and genetic analysis of a child with transcobalamin II deficiency / 中华医学遗传学杂志

OBJECTIVE@#To investigate the genetic etiology, clinical diagnosis and treatment of a child with pancytopenia, failure to thrive and pulmonary infection.@*METHODS@#Peripheral blood samples of the child and her parents were collected. Genomic DNA was extracted. Genetic variants associated with hematological diseases were detected by high-throughput sequencing.@*RESULTS@#Three variants of TCN2 gene were found, one of which located in exon 5 upstream(c.581-8A>T), the parents has carried this variant; one in exon 6 (c.924_927del), the variant was originated from the mother; one in exon 7 (c.973C>T), the variant has ocurred de novo. The variants pathogenic analysis combined with clinical manifestation, pancytopenia, the increase in methylmalonic acid level and increased homocysteine, the child was diagnosed with transcobalaminIIdeficiency. The patient presented with respiratory infection, which was confirmed to be pneumocystosis by lung radioscopy and pathogenic high-throughput sequencing of broncho-alveolar lavage fluid. The patient presented with acute respiratory distress syndrome during the treatment with intramuscular injection of vitamin B@*CONCLUSION@#We reported a case of Chinese child with TCNII deficiency due to novel gene variant, and analyzed the pathogenicity of the three variants. The treatment of TCNII deficiency with cobalamin should be individualized.

Evaluation of propanediol and cobalamin metabolism in the intestinal colonization and systemic invasion of Salmonella Enteritidis in laying hens / [Avaliação do metabolismo do propanodiol e da cobalamina na colonização intestinal e na infecção sistêmica de Salmonella Enteritidis em poedeiras]

Embora Salmonella Enteritidis (SE) seja capaz de metabolizar 1,2-propanodiol (1,2-Pd), utilizado como fonte de carbono e de energia ao longo de uma rota dependente de vitamina B12, a importância deste composto na infeção de Gallus gallus domesticus por SE permanece desconhecida. No presente estudo, foram construídos um mutante de SE sem os genes pduCDE, que codifica a propanodiol desidratase (Pdu), e outro contendo as deleções no pduCDE e também nos genes cobS e cbiA, responsáveis pela síntese de vitamina B12. Em seguida, avaliou-se a importância do metabolismo do 1,2-Pd em SE para colonização intestinal de infecção sistêmica de poedeiras comerciais. As estirpes mutantes de SE foram capazes de colonizar o intestino, de serem excretadas nas fezes e de invadir o baço e o fígado na mesma intensidade que a estirpe selvagem, o que sugere que os produtos dos genes pduC, pduD, pduE, cobS e cbiA não são essenciais durante infecção por Salmonella Enteritidis nessa espécie.(AU)

Association of transcobalamine II gene polymorphisms and serum homocysteine, vitamin Band folate levels with ulcerative colitis among Chinese patients / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To assess the association of transcobalamine II (TCN2) gene polymorphisms and serum levels of homocysteine (Hcy), vitamin Band folate with ulcerative colitis (UC) among Chinese patients.</p><p><b>METHODS</b>For 397 UC patients and 574 controls, two single nucleotide polymorphisms of the TCN2 gene (rs1801198, rs9606756) were tested with an improved multiple ligase detection reaction method. Serum Hcy, vitamin Band folate were measured with an enzymatic cycling assay and an chemiluminescence immunoassay, respectively.</p><p><b>RESULTS</b>The allelic and genotypic frequencies of rs1801198 and rs9606756 did not differ significantly between the two groups (all P> 0.05). Compared with those of the control group, the frequencies of G allele and CG+GG genotype of rs1801198 were greater in patients with moderate and severe UC (both P< 0.05). The same conclusion may also be drawn for the G allele and AG genotype of rs9606756 (both P< 0.05). Compared with the controls, average Hcy level was enhanced in UC patients (P< 0.01), whereas average vitamin Band folate levels were decreased in UC patients (both P< 0.01). In both groups, the average level of Hcy was lower in individuals carrying CC of (rs1801198) than in those with CG+GG (both P< 0.05). A similar conclusion was also drawn for individuals with AA of rs9606756 when compared with those carrying AG(both P< 0.05). Compared with patients with mild UC, average Hcy level was increased in those with moderate and severe UC (P< 0.01), while average vitamin Band folate levels were decreased in those with moderate and severe UC (both P< 0.01). The prevalence of hyperhomocysteinemia(HHcy), vitamin Bdeficiency and folate deficiency was greater in UC patients than in controls (all P< 0.01). In UC patients, the level of Hcy was negatively correlated with those of vitamin B(P< 0.01), albumin(P< 0.01), red blood cells(P< 0.01) and platelet (P< 0.05), but positively correlated with white blood cells(P< 0.01) and Mayo score (P< 0.01). Both HHcy and folate deficiency were independent risk factors for UC (OR=4.173, OR=5.206, both P< 0.01).</p><p><b>CONCLUSION</b>TCN2 (rs1801198, rs9606756) variations, as well as serum levels of Hcy, vitamin Band folate, are correlated with UC. Both HHcy and folate deficiency are independent risk factors for UC.</p>

Estudo de associação de polimorfismos nos genes TCN2 e MTRR e fissura labiopalatina / Association study of polymorphisms in genes TCN2 and MTRR and cleft palate

A fissura de lábio e/ou palato (FL/P) é considerada a anomalia craniofacial mais comum entre os seres humanos. A etiologia da FL/P isolada é complexa e de origem multifatorial, compreendendo diversos fatores genéticos e ambientais. Dentre os fatores ambientais, sabe-se que os déficits nutricionais desempenham um papel fundamental na etiologia dessa anomalia...Os resultados sugerem que os polimorfismos dos genes TCN2 (rs1801198) e MTRR (rs 1801394) não estão associados com FL/P, porém este último gene deve ser melhor investigado em outras populações em função dos resultados limítrofes obtidos. O hábito de fumar durante a gestação foi considerado um forte fator de risco para FL/P.

Association of genetic polymorphisms in methionine metabolism genes with X-linked adrenoleukodystrophy / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the association of the polymorphisms of methionine metabolism genes and the phenotype of X-linked adrenoleukodystrophy (X-ALD) and clinical severity.</p><p><b>METHODS</b>The clinical information of 120 X-ALD patients were analyzed and three genetic variants involved in the methionine metabolism, including cystathionine beta-synthase (CBS) c.844_855ins68, 5-methyltetrahydrofolate-homocysteine-S-methyltransferase (MTR) c.2756A to G, and transcobalamin 2 (TC2) c.776 C to G were analyzed by polymerase chain reaction and sequencing. The association between these polymorphisms and phenotype of X-ALD was studied.</p><p><b>RESULTS</b>The frequency of GG genotype of the TC2 c.776 C/G was higher in patients with central nervous system(CNS) demyelination than in controls (P= 0.012). However, the other two polymorphisms did not show any significant associations with the phenotypes.</p><p><b>CONCLUSION</b>The GG genotype of TC2 c.776 C/G may contribute to X-ALD phenotype.</p>

Relationship between the Levels of Holotranscobalamin and Vitamin B12 / 대한진단검사의학회지

To date, the determination of serum vitamin B12 levels has been the most common laboratory test for the assessment of vitamin B12 status; however, the diagnostic accuracy of this test is low. To obtain a more sensitive marker, a new test to measure holotranscobalamin (holoTC) levels has been introduced. In this study, we assessed 45 patients for whom a vitamin B12 test had been requested and 139 anemic patients. We investigated the associations between the levels of homocysteine (Hcy) and those of holoTC, serum vitamin B12, and folate and assessed the diagnostic value of holoTC levels as a marker for vitamin B12 deficiency. We also determined the precision of the AxSYM holoTC assay by calculating the coefficient of variance (CV). The within-run and between-run precision values were excellent, as all CV values were less than 3.5%. The holoTC levels were low (12 micromol/L) indicated vitamin B12 deficiency. Thus, the holoTC levels were more sensitive than the serum vitamin B12 levels for indicating vitamin B12 status. If the serum vitamin B12 level is 151-300 pmol/L, the levels of holoTC alone or in combination with serum vitamin B12 levels are likely to be more useful markers than serum vitamin B12 levels alone.

A80G polymorphism of reduced folate carrier 1 (RFC1) and C776G polymorphism of transcobalamin 2 (TC2) genes in Down's syndrome etiology / Polimorfismos do gene carregador de folato reduzido (RFC1) A80G e transcobalamina 2 (TC2) C776G na etiologia da síndrome de Down

CONTEXT AND OBJECTIVE: There is evidence that polymorphisms of genes involved in folate metabolism may be associated with higher risk that mothers may bear a Down's syndrome (DS) child. This study therefore had the objective of investigating the A80G polymorphism of the reduced folate carrier 1 (RFC1) gene and the C776G polymorphism of the transcobalamin 2 (TC2) gene as maternal risk factors for DS among Brazilian women. DESIGN AND SETTING: Analytical cross-sectional study with control group, at Faculdade de Medicina de São José do Rio Preto (Famerp). METHODS: Sixty-seven mothers of DS individuals with free trisomy 21, and 113 control mothers, were studied. Molecular analysis of the polymorphisms was performed by means of the polymerase chain reaction with restriction fragment length polymorphism (PCR-RFLP), followed by electrophoresis on 2 percent agarose gel. RESULTS: The frequencies of the polymorphic alleles were 0.51 and 0.52 for RFC1 80G, and 0.34 and 0.34 for TC2 776G, in the case and control groups, respectively. Thus, there were no differences between the groups in relation to either the allele or the genotype frequency, for both polymorphisms (P = 0.696 for RFC1 A80G; P = 0.166 for TC2 C776G; P = 0.268 for combined genotypes). CONCLUSION: There was no evidence of any association between the RFC1 A80G and TC2 C776G polymorphisms and the maternal risk of DS in the sample evaluated.

CONTEXTO E OBJETIVO: Considerando as evidências de que polimorfismos em genes envolvidos no metabolismo do folato podem estar associados ao risco materno elevado para a síndrome de Down (SD), o objetivo deste estudo foi investigar os polimorfismos A80G do gene carregador de folato reduzido 1 (RFC1) e C776G do gene transcobalamina 2 (TC2) como fatores de risco maternos para a SD em mulheres brasileiras. TIPO E ESTUDO LOCAL: Estudo transversal analítico com grupo controle, realizado na Faculdade de Medicina de São José do Rio Preto (Famerp). MÉTODOS: Foram avaliadas 67 mães de indivíduos com trissomia livre do 21 e 113 mães de indivíduos sem a síndrome. A análise molecular dos polimorfismos foi realizada pela técnica de reação em cadeia da polimerase/polimorfismo de comprimento fragmentos de restrição (PCR-RFLP), seguida por eletroforese em gel de agarose 2 por cento. RESULTADOS: As freqüências dos alelos polimórficos foram de 0,51 e 0,52 para RFC1 80G e 0,34 e 0,34 para TC2 776G nos grupos caso e controle, respectivamente. Assim, não houve diferença nas freqüências alélicas e genotípicas para ambos os polimorfismos entre os grupos (P = 0,696 para RFC1 A80G; P = 0,166 para TC2 C776G; p = 0,268 para genótipos combinados). CONCLUSÃO: Não há evidência de associação entre os polimorfismos RFC1 A80G e TC2 C776G e o risco materno para a SD na casuística avaliada.

Study on serum transcobalamin II in patients with murine typhus.

We measured the serum transcobalamin II in murine typhus- infected patients (n = 16) admitted to the Hospital for Tropical Diseases in 1996-1997, compared with healthy controls (n = 60). The results showed that the transcobalamin II (TCII) and total serum unsaturated vitaminB12 binding capacity (UBBC) in patients with murine typhus (2,126.5 pg/ml, range 1,262-4,568 and 3,771.5 pg/ml, range 1,576-6,763 pg/ml) were statistically significantly higher than normal subjects (987.5 pg/ml, range 678-2,000 pg/ml and 1,402 pg/ml, range 932-2,470 ml) (p<0.001). Serum TCII levels in patients (63%) were elevated during the febrile period and returned to normal post-treatment. These findings suggest that patients with murine typhus had stimulation of reticulo-endothelial system, spleen, mesenteric lymph nodes, liver and skin and then released TCII into the blood circulation. The elevation in TCII may be used for confirming a diagnosis of murine typhus.

Fisiopatologia da deficiência de vitamina B12 e seu diagnóstico laboratorial / Physiopathology of vitamin B12 deficiency and its laboratorial diagnosis

INTRODUÇAO: A vitamina B12 é hidrossolúvel, não-sintetizada pelo organismo humano, presente em alimentos de origem animal. Sua deficiência é muito freqüente entre idosos, vegetarianos e indivíduos que adotam baixa dieta protéica ou apresentam problemas de absorção gastrintestinal. FISIOPATOLOGIA: A deficiência de vitamina B12 leva a transtornos hematológicos, neurológicos e cardiovasculares, principalmente, por interferir no metabolismo da homocisteína (Hcy) e nas reações de metilação do organismo. Muitas vezes a deficiência pode permanecer assintomática por longos períodos, desencadeando uma deficiência crônica que, se mantida, pode levar a manifestações neurológicas irreversíveis. METODOLOGIAS: Metodologias eficientes que permitam um diagnóstico precoce são imprescindíveis. Porém um método considerado padrão-ouro ainda não é consensual. A dosagem sérica de vitamina B12 sofre algumas restrições pelos problemas de sensibilidade e especificidade, podendo ocorrer sintomas de deficiência mesmo com vitamina B12 sérica dentro dos níveis normais ou, de outro modo, ocorrendo baixos níveis de vitamina B12 sérica sem, contudo, apresentar baixos níveis da fração de vitamina realmente disponível para as células e sem apresentar sintomatologia. Novas alternativas vêm surgindo, como a dosagem de transcobalamina II (Tc II), a única fração de vitamina B12 disponível para as células, ou a dosagem de ácido metilmalônico (MMA) e Hcy, metabólitos que aumentam quando ocorre diminuição de vitamina B12 intracelular. Estes testes apresentam algumas vantagens, mas também limitações importantes para uso rotineiro. CONCLUSAO: Em casos subclínicos, um diagnóstico correto e precoce representa ainda um desafio, e futuros estudos são necessários para definir um método padrão para diagnóstico laboratorial da deficiência de vitamina B12.

Elevation of serum transcobalamin II in patients with scrub typhus.

Serum transcobalamin II levels were measured in scrub typhus patients. Eighteen out of fifty-two patients admitted to Maharat Nakhon Ratchasima Hospital were diagnosed with scrub typhus infection. The serum unsaturated vitamin B12 binding protein (UBBC) and total vitamin B12 binding protein (TBBC) levels in these patients were significantly higher than in normal subjects (p < 0.001). The mean serum transcobalamin II level in the typhus patients was also significantly higher than in the normal subjects (p=0.004). There was a significant correlation between serum TCII levels and typhus IgM or IgG titers (p < 0.05), but not to total IgM levels. These findings indicate that patients with scrub typhus had stimulation of the recticuloendothelial system as a result of a considerable increase in transcobalamin II levels.

Linkage analysis of a large inbred family with congenital megaloblastic anemia

Megaloblastic anemia during infancy and early childhood often reflects a hereditary disorder of cobalamin's absorption, transport, or intracellular metabolism. There are 3 well defined autosomal recessive syndromes manifesting with megaloblastic anemia due to defects in cobalamin absorption or transport, namely congenital pernicious anemia, Imerslund-Grasbeck syndrome and Transcobalamin II deficiency. The genes responsible for the 3 disorders are gene intrinsic factor [GIF], MGA1 and TCN2, as well as the gene for Transcobalamin I, TCN1 are mapped or cloned, or both. We describe the clinical picture of 7 patients from 3 sibships, belong to one large inbred family who presented with megaloblastic anemia during infancy. The mode of inheritance follows an autosomal recessive pattern and the syndrome was completely reversed by parentral vitamin B12 therapy. The ascertainment of the family was carried out in 1998 in the Princess Rhama Children's Hospital, which is affiliated with Jordan University of Science and Technology, Jordan. We performed linkage analysis in this family for genes or regions involved in the above mentioned disorders. The genes implicated in the etiology of the previously mentioned disorders were excluded from being responsible for the disorder in this family. The exclusion of the involvement of GIF, MGA1, TCN1 and TCN2 in this family suggests that another gene and its product, involved in cobalamin absorption or transport, remains to be identified. A genome-wide search of the gene implicated in this family may give some insight on that gene, and its function

Serum transcobalamin II level in glucose-6-phosphate dehydrogenase deficient subjects with typhoid fever.

Transcobalamin II (TCII) is the vitamin B12 binding protein which is responsible for delivery of this vitamin to the tissues. High values for serum TCII have been reported in many clinical conditions. This paper describes the elevated serum TCII levels in three G-6-PD deficient patients with typhoid fever. They had severe hemolysis with hemoglobinuria associated with slight liver dysfunctions but without obvious increased serum creatinine and BUN concentrations. A remarkable increase in serum TCII level was observed during active hemolysis and decreased to the normal level within 2-3 days after hemolysis ceased. The mechanism of increased serum TCII during hemolysis is probably due to hemoglobinuria secondary to excessive hemolysis. As Hb is known to be efficiently reabsorbed by the proximal tubule cells and can competitively inhibit the tubular uptake of TCII-B12. It is possible that excess Hb interferes with TCII uptake and degradation at renal tubular cells. Therefore, the circulating TCII survival is prolonged resulting in the elevated TCII level. Furthermore, lysosomal degradation of newly synthesized TCII is a normal process that regulates the TCII secretion. Therefore, a reduced lysosome-mediated uptake of TCII-B12 by renal tubular cell may stimulate the TCII secretion as has been shown experimentally in vitro.

Serum transcobalamin II levels in patients with acute and chronic renal failure.

Serum TCII levels were determined in 57 patients with acute and chronic renal failure. They were divided into 3 groups, group I was malarial patients with acute renal failure, group II and III were patients with acute renal failure and chronic renal failure from other underlying causes, respectively. All patients in group I had serum TCII over 2000 pg/ml while these values were within the normal limits in the other 2 groups. These findings indicated that elevated serum TCII occurred only in malarial patients with acute renal failure. The clearance and urinary excretion of TCII in malarial patients were found to be lower and increased to the normal levels after recovery from azotemia, indicating that the failure of excretion of TCII by the kidneys may be responsible for elevated serum TCII levels. The pathophysiological changes in the kidneys in malarial patients may reduce the amount of filtered TCII-B12 through the glomeruli and decrease TCII-B12 uptake by the renal tubules resulting in the decreased TCII degradation by tubular cells. Therefore, the intravascular TCII survival is prolonged with elevated serum TCII levels in these patients.

Serum transcobalamin II levels in patients with malaria infection.

Serum transcobalamin II (TCII) levels were determined in 56 patients with P. falciparum malaria infection. They were divided into 3 groups: severe (malarial parasite > 5% or patients with cerebral malaria or renal insufficiency), moderate (1-5% infection without complications) and mild (1% infection). Elevated serum TCII values were found only in patients with severe malaria infection. These values correlated directly with parasitemia, blood urea nitrogen and creatinine, but were not correlated with alkaline phosphatase. As 17 patients with azotemia had elevated serum TCII levels while other 3 patients with normal BUN and creatinine concentrations had serum TCII levels within the normal limits. These findings indicated that malarial patients with renal insufficiency had increased serum TCII. A possible mechanism is the reduced TCII-B12 that filtered through the glomeruli due to the reduced renal blood flow with the decreased its uptake by proximal tubular cells resulting in the decreased degradation of TCII by the tubular lysosomal enzymes. Determination of serum TCII level may be used as an indicator of renal function in malarial patients with renal insufficiency.

Persistently elevated serum transcobalamin II in a patient with cerebral malaria and typhus infections.

A 25-year-old man presented with a history of fever, chills and vomiting for three days. The parasite count was 207 ring-forms of P. falciparum per 1000 red cells. He developed hemoglobinuria and excreted hemoglobin in the urine 0.20-0.30 g/dl for 14 days during admission. Many blood transfusions were administered for correcting anemia. Although the malarial parasites disappeared one week after anti-malarial therapy, however, the fever and hemoglobinuria persisted. The Weil-Felix reaction OXK was positive with a titre of 1:40 on admission and increased to 1:160 on the second week. Chloramphenical and prednisolone were given for treatment of typhus fever and all symptoms subsided. Serum TCII levels were found to be increased and persisted high during the hemoglobinuria. The clearance of TCII was lower and increased relatively slowly to the normal level on day 30. On the other hand, TCII excretion in the urine was found to be increased during hemoglobinuria. These findings indicate that the catabolism and clearance of TCII in this patients is impaired with increased TCII excretion in the urine in parallel to the hemoglobinuria. Serum TCII level is, therefore, increased and persistently high in a patient with malaria and typhus fever infections with hemoglobinuria.

Abnormally elevated serum transcobalamin II levels in patients with cerebral malaria.

Transcobalamin II (TCII) levels have been reported to be elevated in patients with many clinical conditions including proliferative reticuloendothelial system. As reactive macrophage hyperplasia frequently occurs in patients with malaria, the objective of the present study was to determine TCII in patients with Plasmodium falciparum with cerebral symptoms. The studies were performed on 14 cerebral malaria patients as well as 60 normal subjects. The mean values of serum vitamin B12 and TCII levels were significantly higher in the patient group and 6 and 7 patients had serum vitamin B12 and TCII levels higher than the normal values. There was direct relationship between serum TCII levels and BUN or creatinine levels. These findings indicated that raised serum TCII level occurred only in patients with renal insufficiency. A decreased glomerular fiLtration rate reduced the amount of vitamin B12 and TCII-B12 that filtered through the glomeruli resulting in the reduced proximal tubular cells uptake and its degradation of TCII. This reduced lysosomal enzyme activity, therefore, prolongs the intravascular TCII survival and increased secretion of TCII into the circulation. Therefore, serum TCII levels were elevated in these cerebral malaria patients.

Estudio de la vitamina B12 y sus transportadores en la leucemia aguda y síndrome mieloproliferativo / Study of vitamin B12 and its carriers in acute leukemia and myeloproliferative syndrome

Se realizaron determinaciones de la vitamina B12 y sus proteínas transportadoras en un grupo de pacientes con leucemia aguda y síndrome mieloproliferativo y los resultados se compararaon con un grupo control. El grupo con policitemia vera se compara con 5 pacientes que padecen de policitemia secundaria. Se encontró un aumento de la capacidad latente de unión (UBBC) dependiente de la transcobalamina II en los pacientes con leucemia aguda. Igual resultado se encontró en aquéllos con leucemia mieloide crónica y policitemia vera, pero en éstos dicha elevación se debió a un aumento conjunto de los niveles de transcobalamina I y II (ARBC). Los resultados obtenidos en los pacientes con leucemia mieloide crónica, que fueron estudiados evolutivamente, sugieren que la vitamina B12 y sus proteínas transportadoras pueden ser un elemento que se deba considerar para decidir la duración del tratamiento de esta enfermedad