Two novel mutations in TMPRSS6 associated with iron-refractory iron deficiency anemia in a mother and child.
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ABSTRACT:
SUBMITTER: Yaish HM
PROVIDER: S-EPMC5656052 | biostudies-literature | 2017 Jun
REPOSITORIES: biostudies-literature
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Two novel mutations in TMPRSS6 associated with iron-refractory iron deficiency anemia in a mother and child.
Yaish Hassan M HM Farrell Colin P CP Christensen Robert D RD MacQueen Brianna C BC Jackson Laurie K LK Trochez-Enciso Jesus J Kaplan Jerry J Ward Diane M DM Salah Walid K WK Phillips John D JD
Blood cells, molecules & diseases 20170409
In an iron deficient child, oral iron repeatedly failed to improve the condition. Whole exome sequencing identified one previously reported plus two novel mutation in the TMPRSS6 gene, with no mutations in other iron-associated genes. We propose that these mutations result in a novel variety of iron-refractory iron deficiency anemia. ...[more]
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Project description:Iron deficiency is usually attributed to chronic blood loss or inadequate dietary intake. Here, we show that iron deficiency anemia refractory to oral iron therapy can be caused by germline mutations in TMPRSS6, which encodes a type II transmembrane serine protease produced by the liver that regulates the expression of the systemic iron regulatory hormone hepcidin. These findings demonstrate that TMPRSS6 is essential for normal systemic iron homeostasis in humans.
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Project description:Iron is essential for life because it is indispensable for several biological reactions, such as oxygen transport, DNA synthesis, and cell proliferation. Over the past few years, our understanding of iron metabolism and its regulation has changed dramatically. New disorders of iron metabolism have emerged, and the role of iron as a cofactor in other disorders has begun to be recognized. The study of genetic conditions such as hemochromatosis and iron-refractory iron deficiency anemia (IRIDA) has provided crucial insights into the molecular mechanisms controlling iron homeostasis. In the future, these advances may be exploited to improve treatment of both genetic and acquired iron disorders. IRIDA is caused by mutations in TMPRSS6, the gene encoding matriptase-2, which downregulates hepcidin expression under conditions of iron deficiency. The typical features of this disorder are hypochromic, microcytic anemia with a very low mean corpuscular volume of erythrocytes, low transferrin saturation, no (or inadequate) response to oral iron, and only a partial response to parenteral iron. In contrast to classic iron deficiency anemia, serum ferritin levels are usually low-normal, and serum or urinary hepcidin levels are inappropriately high for the degree of anemia. Although the number of cases reported thus far in the literature does not exceed 100, this disorder is considered the most common of the "atypical" microcytic anemias. The aim of this review is to share the current knowledge on IRIDA and increase awareness in this field.
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Project description:TMPRSS6 variants that affect protein function result in impaired matriptase-2 function and consequently uninhibited hepcidin production, leading to iron refractory iron deficiency anemia (IRIDA). This disease is characterized by microcytic, hypochromic anemia and serum hepcidin values that are inappropriately high for body iron levels. Much is still unknown about its pathophysiology, genotype-phenotype correlation, and optimal clinical management. We describe 14 different TMPRSS6 variants, of which 9 are novel, in 21 phenotypically affected IRIDA patients from 20 families living in the Netherlands; 16 out of 21 patients were female. In 7 out of 21 cases DNA sequencing and multiplex ligation dependent probe amplification demonstrated only heterozygous TMPRSS6 variants. The age at presentation, disease severity, and response to iron supplementation were highly variable, even for patients and relatives with similar TMPRSS6 genotypes. Mono-allelic IRIDA patients had a milder phenotype with respect to hemoglobin and MCV and presented significantly later in life with anemia than bi-allelic patients. Transferrin saturation (TSAT)/hepcidin ratios were lower in IRIDA probands than in healthy relatives. Most patients required parenteral iron. Genotype alone was not predictive for the response to oral iron. We conclude that IRIDA is a genotypically and phenotypically heterogeneous disease. The high proportion of female patients and the discrepancy between phenotypes of probands and relatives with the same genotype, suggest a complex interplay between genetic and acquired factors in the pathogenesis of IRIDA. In the absence of inflammation, the TSAT/hepcidin ratio is a promising diagnostic tool, even after iron supplementation has been given. Am. J. Hematol. 91:E482-E490, 2016. © 2016 Wiley Periodicals, Inc.
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Project description: Not available
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Project description:BackgroundGenome-wide-association studies have identified the TMPRSS6 polymorphism rs855791 has the strongest association with red blood cell indices or iron parameters in general population. Whether this genetic variant influences the susceptibility of iron deficiency anemia (IDA) in women with menstruation has not been well studied.MethodsIn this case-control study, we enrolled 67 women with IDA and 107 healthy volunteers, and analyzed their complete blood counts, rs855791 genotypes, and menstrual amounts. Menstrual blood loss was evaluated with a pictorial blood-loss assessment chart.ResultsThere were significantly fewer rs855791 C homozygotes in the IDA group than in the healthy group (11.9% vs. 25.2%, p = 0.03). The odds ratio (OR) of C homozygotes having IDA versus non-CC subjects having IDA was 0.4 (95% CI, 0.17 - 0.95, p = 0.04). When the analysis was confined to study subjects with menorrhagia, this difference became more prominent (9.6% vs. 28.6%, p = 0.01; OR, 0.27, 95% CI, 0.09 - 0.77, p = 0.01). For women with non-CC genotypes, there was an inverse correlation between hemoglobin levels and menstrual loss (p < 0.001); however, this association was not found for those with genotypes CC (p = 0.15).ConclusionsOur study suggests homozygosity for TMPRSS6 rs855791 C genotype has a protective role against IDA in women at reproductive age, especially in those with menorrhagia.
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Project description:Iron-refractory iron-deficiency anemia (IRIDA) is an autosomal recessive disorder caused by mutations in TMPRSS6. Patients have hypochromic microcytic anemia refractory to oral iron and are only partially responsive to parenteral iron administration. We report a French-Canadian kindred in which 2 siblings presented in early childhood with severe microcytic anemia, hypoferremia, and hyperferritinemia. Both children have been successfully treated solely with low-dose oral iron since diagnosis. Clinical and biological presentation did not fit any previously described genetic iron-deficiency anemia. Whole exome sequencing identified in both patients compound heterozygous mutations of TMPRSS6 leading to p.G442R and p.E522K, 2 mutations previously reported to cause classic IRIDA, and no additional mutations in known iron-regulatory genes. Thus, the phenotype associated with the unique combination of mutations uncovered in both patients expands the spectrum of disease associated with TMPRSS6 mutations to include iron deficiency anemia that is accompanied by hyperferritinemia at initial presentation and is responsive to continued oral iron therapy. Our results have implications for genetic testing in early childhood iron deficiency anemia. Importantly, they emphasize that whole exome sequencing can be used as a diagnostic tool and greatly facilitate the elucidation of the genetic basis of unusual clinical presentations, including hypomorphic mutations or compound heterozygosity leading to different phenotypes in known Mendelian diseases.
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