Inter-ethnic differences in genetic variants within the transmembrane protease, serine 6 (TMPRSS6) gene associated with iron status indicators: a systematic review with meta-analyses

The role of TMPRSS6 gene polymorphism in iron resistance iron deficiency anaemia (IRIDA): a systematic review

Iron resistance iron deficiency anaemia is a rare autosomal recessive disorder characterized by hypochromic microcytic anaemia, low transferrin saturation and inappropriately high hepcidin levels. The aetiology of this condition is rooted in genetic variations within the transmembrane serine protease 6 (TMPRSS6) genes, responsible for encoding matriptase-2, a pivotal negative regulator of hepcidin. We conducted a systematic search across four electronic databases, yielding 538 articles in total out of which 25 were finally included and were preceded further, aiming to prognosticate prevalent single nucleotide polymorphisms (SNPs) and detrimental genetic alterations. This review aims to elucidate the effects of various SNPs and pathogenic mutations on both haematological and biochemical parameters, as well as their potential interethnic correlation. Employing bioinformatics tools, we subjected over 100 SNPs to scrutiny, discerning their potential functional ramifications. We found rs1373272804, rs1430692214 and rs855791 variants to be most frequent and were having a significant impact on haematological and biochemical profile. We found that individuals of European ancestry were more prone to have these variants compared to other ethnic groups. In conclusion, this review not only sheds light on the association of TMPRSS6 polymorphism in iron resistance iron deficiency anaemia (IRIDA), but also highlights the critical need for further investigations involving larger sample size and more diverse ethnic groups around the globe. These future studies will be vital for gaining a stronger and more reliable understanding of how these genetic differences are linked to the development of IRIDA.

Biology of Anemia: A Public Health Perspective

Our goal is to present recent progress in understanding the biological mechanisms underlying anemia from a public health perspective. We describe important advances in understanding common causes of anemia and their interactions, including iron deficiency (ID), lack of other micronutrients, infection, inflammation, and genetic conditions. ID develops if the iron circulating in the blood cannot provide the amounts required for red blood cell production and tissue needs. ID anemia develops as iron-limited red blood cell production fails to maintain the hemoglobin concentration above the threshold used to define anemia. Globally, absolute ID (absent or reduced body iron stores that do not meet the need for iron of an individual but may respond to iron supplementation) contributes to only a limited proportion of anemia. Functional ID (adequate or increased iron stores that cannot meet the need for iron because of the effects of infection or inflammation and does not respond to iron supplementation) is frequently responsible for anemia in low- and middle-income countries. Absolute and functional ID may coexist. We highlight continued improvement in understanding the roles of infections and inflammation in causing a large proportion of anemia. Deficiencies of nutrients other than iron are less common but important in some settings. The importance of genetic conditions as causes of anemia depends upon the specific inherited red blood cell abnormalities and their prevalence in the settings examined. From a public health perspective, each setting has a distinctive composition of components underlying the common causes of anemia. We emphasize the coincidence between regions with a high prevalence of anemia attributed to ID (both absolute and functional), those with endemic infections, and those with widespread genetic conditions affecting red blood cells, especially in sub-Saharan Africa and regions in Asia and Oceania.

Genetic Variations of ferroportin-1(FPN1-8CG), TMPRSS6 (rs855791) and Hemojuvelin (I222N and G320V) Among a Cohort of Egyptian β-Thalassemia Major Patients

Iron overload remains a major cause of morbidity and mortality among β-thalassemia major (β-TM) patients. Iron regulatory proteins and their genetic variants together with changes in hepcidin levels in thalassemic patients could affect the disease manifestations. This work aimed to study genetic variations of ferroportin-1 (FPN1-8CG), Transmembrane Serine Protease 6 (TMPRSS6 rs855791) and hemojuvelin (HJV I222N and G320V) genes within a cohort of 97 β-TM Egyptian patients by Polymerase chain reaction Restriction Fragment Length Polymorphism (PCR-RFLP) in comparison to fifty normal control subjects. Among β-TM patients; the CG variant of FPN1 was significantly higher, while the TT and TC variants of TMPRSS6 were significantly lower in comparison to controls. Liver Iron Concentration (LIC) was significantly higher among β-TM patients harboring the FPN1 (GG) genotype and we found that FPN1gene mutation acts as independent predictor of MRI LIC (p = 0.011), Pulmonary artery pressure (PAP) was significantly higher in patients harboring the mutant FPN1 (GG and CG) genotypes (p value 0.04). β-TM patients having the HJV I222N (AA) genotype were having significantly higher cardiac iron overload (p value = 0.026). The studied genetic variants of iron regulatory proteins could alter the manifestations of iron overload thus resulting in different clinical phenotypes of thalassemic patients, these findings need to be confirmed by larger cohorts of patients with longer follow-up periods.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12288-022-01580-8.

Common and ethnic-specific genetic determinants of hemoglobin concentration between Taiwanese Han Chinese and European Whites: findings from comparative two-stage genome-wide association studies

Human iron nutrition is a result of interplays between genetic and environmental factors. However, there has been scarcity of data on the genetic variants associated with altered iron homeostasis and ethnic-specific associations are further lacking. In this study, we compared between the Taiwanese Han Chinese (HC) and European Whites the genetic determinants of hemoglobin (Hb) concentration, a biochemical parameter that in part reflects the amount of functional iron in the body. Through sex-specific two-stage genome-wide association studies (2S-GWAS), we observed the consistent Hb-association of SNPs in TMPRSS6 (chr 22), ABO (chr 9), and PRKCE (chr 2) across sexes in both ethnic groups. Specific to the Taiwanese HC, the Hb-association of AXIN1, together with other loci near the chr 16 alpha-globin gene cluster, was found novel. On the other hand, majority of the Hb-associated SNPs among Europeans were identified along the chr 6 major histocompatibility complex (MHC) region, which has established roles in immune system control. We report here strong Hb-associations of HFE and members of gene families (SLC17; H2A, H2B, H3, H4, H1; TRIM; ZSCAN, ZKSCAN, ZNF; HLA; BTN, OR), numerous SNPs in/nearby CARMIL1, PRRC2A, PSORS1C1, NOTCH4, TSBP1, C6orf15, and distinct associations with non-coding RNA genes. Our findings provide evidence for both common and ethnic-specific genetic determinants of Hb between East Asians and Caucasians. These will help to further our understanding of the iron and/or erythropoiesis physiology in humans and to identify high risk subgroups for iron imbalances - a primary requirement to meet the goal of precision nutrition for optimal health.

Associated Effect of SLC40A1 and TMPRSS6 Polymorphisms on Iron Overload

Mutations in the ferroportin (FPN) gene SLC40A1 alter iron recycling and cause disturbances in iron homeostasis. The variants of TMPRSS6 contribute to the development of iron deficiencies. In this study, we determined the role of FPN and TMPRSS6 gene polymorphisms in the modulation of iron homeostasis based on biochemical parameters. PCR analysis and sequencing were performed to determine the single nucleotide polymorphisms (SNPs) SLC40A1 c.44−24G>C (rs1439816), SLC40A1 c.663T>C (rs2304704), and TMPRSS6 c.2207T>C (rs855791). Hemoglobin concentration and iron status were determined by standard procedures. We studied 79 iron-loaded individuals for SLC40A1 polymorphisms. Interestingly, 35/79 individuals with SLC40A1 SNPs also carried a TMPRSS6 c.2207T>C polymorphism. The biochemical values of the iron overloaded individuals were compared to those of the individuals carrying TMPRSS6 SNPs and the healthy individuals (wild-type group). The ferritin concentration, transferrin saturation % (TS%), and hemoglobin concentration were significantly higher in the participants with FPN SNPs than in the other three groups. The ferritin concentration and TS% were higher in participants with both SLC40A1 and TMPRSS6 SNPs than in the TMPRSS6 and wild-type groups, while hemoglobin concentration was significantly higher than that in the TMPRSS6 SNP group only. The participants with TMPRSS6 SNPs had significantly lower ferritin concentration, TS%, and hemoglobin concentration than all the other groups. SLC40A1 and TMPRSS6 SNPs might act in the opposite direction, preventing the development of severe iron overload, and the modulation of the iron status by TMPRSS6 SNPs might provide protection.

Effects of probiotics on immunity and iron homeostasis: A mini-review

Iron deficiency remains a major problem in both developed and developing countries. Iron supplementation has been used as a standard intervention for the prevention and treatment of iron deficiency anemia (IDA). There are many factors affecting the efficacy, including stunting, infections or inflammations, and genetics. Recently, some studies have been conducted to further investigate the effects of probiotics on immunity and iron homeostasis. This mini review discusses about some important factors that can improve the management of IDA.

New Insights into Iron Deficiency Anemia in Children: A Practical Review

Iron deficiency anemia (IDA) is the most frequent hematological disorder in children, with an incidence in industrialized countries of 20.1% between 0 and 4 years of age and 5.9% between 5 and 14 years (39 and 48.1% in developing countries). Although IDA has been recognized for a long time, there are still uncovered issues and room for improving the management of this condition. New frontiers regarding its diagnosis and therapeutic options emerge every day; recently, innovative formulations of iron have been launched, both for oral and parenteral administration, with the aim of offering treatment schedules with higher efficacy and lower toxicity. As a matter of fact, glycinate and liposomal preparations, while maintaining a satisfying efficacy profile, have significantly fewer side effects, in comparison to the traditional elemental iron salts; parenteral iron, usually considered a second-choice therapy reserved to selected cases, may evolve further, as a consequence of the production of molecules with an interesting clinical profile such as ferrocarboxymaltose, which is already available for adolescents aged >14 years. The present article reports the clinically relevant latest insights regarding IDA in children and offers a practical guide to help pediatricians, particularly to choose the most appropriate prevention and therapy strategies.

Iron Deficiency in Heart Failure: Mechanisms and Pathophysiology

Iron is an essential micronutrient for a myriad of physiological processes in the body beyond erythropoiesis. Iron deficiency (ID) is a common comorbidity in patients with heart failure (HF), with a prevalence reaching up to 59% even in non-anaemic patients. ID impairs exercise capacity, reduces the quality of life, increases hospitalisation rate and mortality risk regardless of anaemia. Intravenously correcting ID has emerged as a promising treatment in HF as it has been shown to alleviate symptoms, improve quality of life and exercise capacity and reduce hospitalisations. However, the pathophysiology of ID in HF remains poorly characterised. Recognition of ID in HF triggered more research with the aim to explain how correcting ID improves HF status as well as the underlying causes of ID in the first place. In the past few years, significant progress has been made in understanding iron homeostasis by characterising the role of the iron-regulating hormone hepcidin, the effects of ID on skeletal and cardiac myocytes, kidneys and the immune system. In this review, we summarise the current knowledge and recent advances in the pathophysiology of ID in heart failure, the deleterious systemic and cellular consequences of ID.

Distribution and Associated Factors of Hepatic Iron-A Population-Based Imaging Study

Hepatic iron overload can cause severe organ damage; therefore, an early diagnosis and the identification of potential risk factors is crucial. We aimed to investigate the sex-specific distribution of hepatic iron content (HIC) in a population-based cohort and identify relevant associated factors from a panel of markers. We analyzed N = 353 participants from a cross-sectional sample (KORA FF4) who underwent whole-body magnetic resonance imaging. HIC was assessed by single-voxel spectroscopy with a high-speed T2-corrected multi-echo technique. A large panel of markers, including anthropometric, genetic, and laboratory values, as well as behavioral risk factors were assessed. Relevant factors associated with HIC were identified by variable selection based on LASSO regression with bootstrap resampling. HIC in the study sample (mean age at examination: 56.0 years, 58.4% men) was significantly lower in women (mean ± SD: 39.2 ± 4.1 s^-1) than in men (41.8 ± 4.7 s^-1, p < 0.001). Relevant factors associated with HIC were HbA1c as well as prediabetes for men and visceral adipose tissue as well as age for women. Hepatic fat, alcohol consumption, and genetic risk score for iron levels were associated with HIC in both sexes. In conclusion, there are sex-specific associations of HIC with markers of body composition, glucose metabolism, and alcohol consumption.

Association of SNPs within TMPRSS6 and BMP2 genes with iron deficiency status in Saudi Arabia

BACKGROUND

Globally, iron-deficiency anemia (IDA) remains a major health obstacle. This health condition has been identified in 47% of pre-school students (aged 0 to 5 years), 42% of pregnant females, and 30% of non-pregnant females (aged 15 to 50 years) worldwide according to the WHO. Environmental and genetic factors play a crucial role in the development of IDA; genetic testing has revealed the association of a number of polymorphisms with iron status and serum ferritin.

AIM

The current study aims to reveal the association of TMPRSS6 rs141312 and BMP2 rs235756 with the iron status of females in Saudi Arabia.

METHODS

A cohort of 108 female university students aged 18-25 years was randomly selected to participate: 50 healthy and 58 classified as iron deficient. A 3-5 mL sample of blood was collected from each one and analyzed based on hematological and biochemical iron status followed by genotyping by PCR.

RESULTS

The genotype distribution of TMPRSS6 rs141312 was 8% (TT), 88% (TC) and 4% (CC) in the healthy group compared with 3.45% (TT), 89.66% (TC) and 6.89% (CC) in the iron-deficient group (P = 0.492), an insignificant difference in the allelic distribution. The genotype distribution of BMP2 rs235756 was 8% (TT), 90% (TC) and 2% (CC) in the healthy group compared with 3.45% (TT), 82.76% (TC) and 13.79% (CC) in iron-deficient group (P = 0.050) and was significantly associated with decreased ferritin status (P = 0.050). In addition, TMPRSS6 rs141312 is significantly (P<0.001) associated with dominant genotypes (TC+CC) and increased risk of IDA while BMP2 rs235756 is significantly (P<0.026) associated with recessive homozygote CC genotypes and increased risk of IDA.

CONCLUSION

Our finding potentially helps in the early prediction of iron deficiency in females through the genetic testing.

Ethnic Differences in Iron Status

Iron is unique among all minerals in that humans have no regulatable excretory pathway to eliminate excess iron after it is absorbed. Iron deficiency anemia occurs when absorbed iron is not sufficient to meet body iron demands, whereas iron overload and subsequent deposition of iron in key organs occur when absorbed iron exceeds body iron demands. Over time, iron accumulation in the body can increase risk of chronic diseases, including cirrhosis, diabetes, and heart failure. To date, only ∼30% of the interindividual variability in iron absorption can be captured by iron status biomarkers or iron regulatory hormones. Much of the regulation of iron absorption may be under genetic control, but these pathways have yet to be fully elucidated. Genome-wide and candidate gene association studies have identified several genetic variants that are associated with variations in iron status, but the majority of these data were generated in European populations. The purpose of this review is to summarize genetic variants that have been associated with alterations in iron status and to highlight the influence of ethnicity on the risk of iron deficiency or overload. Using extant data in the literature, linear mixed-effects models were constructed to explore ethnic differences in iron status biomarkers. This approach found that East Asians had significantly higher concentrations of iron status indicators (serum ferritin, transferrin saturation, and hemoglobin) than Europeans, African Americans, or South Asians. African Americans exhibited significantly lower hemoglobin concentrations compared with other ethnic groups. Further studies of the genetic basis for ethnic differences in iron metabolism and on how it affects disease susceptibility among different ethnic groups are needed to inform population-specific recommendations and personalized nutrition interventions for iron-related disorders.

Common Variants in the TMPRSS6 Gene Alter Hepcidin but not Plasma Iron in Response to Oral Iron in Healthy Gambian Adults: A Recall-by-Genotype Study

BACKGROUND

The role of genetic determinants in mediating iron status in Africans is not fully understood. Genome-wide association studies in non-African populations have revealed genetic variants in the transmembrane protease serine 6 gene (TMPRSS6) that are associated with the risk of anemia.

OBJECTIVES

To investigate the effects of risk alleles for low iron status, namely TMPRSS6 rs2235321, rs855791, and rs4820268, on responses to oral iron in healthy Gambian adults.

METHODS

Using a recall-by-genotype design, participants were selected from a pregenotype cohort of 3000 individuals in the Keneba Biobank (Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine). Participants were invited to participate in the study based on 9 genotype combinations obtained from 3 TMPRSS6 single nucleotide polymorphisms (SNPs): rs2235321, rs855791, and rs4820268. The participants fasted overnight and then ingested a single oral dose of ferrous sulfate (130 mg elemental iron). Blood samples were collected prior to iron ingestion and at 2 and 5 h after the oral iron dose. The effects of genotype on hepcidin and plasma iron parameters were assessed.

RESULTS

A total of 251 individuals were enrolled. Homozygous carriers of the major TMPRSS6 alleles at each of the SNPs had higher plasma hepcidin at baseline (rs2235321: GG compared with AA = 9.50 compared with 6.60 ng/ml, P = 0.035; rs855791: GG compared with AG = 9.50 compared with 4.96 ng/mL, P = 0.015; rs4820268: AA compared with GG = 9.50 compared with 3.27 ng/mL,  P = 0.002) and at subsequent timepoints. In most subjects, hepcidin concentrations increased following iron ingestion (overall group mean = 4.98 ± 0.98 ng/mL at 5 h, P < 0.001), but double heterozygotes at rs2235321 and rs855791 showed no increase (0.36 ± 0.40 ng/mL at 5 h, P = 0.667).

CONCLUSIONS

This study revealed that common TMPRSS6 variants influence hepcidin concentrations, but not iron status indicators either at baseline or following a large oral dose of iron. These results suggest that genetic variations in the TMPRSS6 gene are unlikely to be important contributors to variations in iron status in Africans.This study was registered at clinicaltrials.gov (# NCT03341338).

Iron deficiency

Iron deficiency is one of the leading contributors to the global burden of disease, and particularly affects children, premenopausal women, and people in low-income and middle-income countries. Anaemia is one of many consequences of iron deficiency, and clinical and functional impairments can occur in the absence of anaemia. Iron deprivation from erythroblasts and other tissues occurs when total body stores of iron are low or when inflammation causes withholding of iron from the plasma, particularly through the action of hepcidin, the main regulator of systemic iron homoeostasis. Oral iron therapy is the first line of treatment in most cases. Hepcidin upregulation by oral iron supplementation limits the absorption efficiency of high-dose oral iron supplementation, and of oral iron during inflammation. Modern parenteral iron formulations have substantially altered iron treatment and enable rapid, safe total-dose iron replacement. An underlying cause should be sought in all patients presenting with iron deficiency: screening for coeliac disease should be considered routinely, and endoscopic investigation to exclude bleeding gastrointestinal lesions is warranted in men and postmenopausal women presenting with iron deficiency anaemia. Iron supplementation programmes in low-income countries comprise part of the solution to meeting WHO Global Nutrition Targets.

Study the association of transmembrane serine protease 6 gene polymorphisms with iron deficiency status in Saudi Arabia

BACKGROUND

Intheclinical setting, iron deficiencyanaemia(IDA) represents a majorglobalhealthconcern. This health condition is reported in 30% of non-pregnant women, 42% of pregnant women (aged 15-50 years), 12.7% of men (15 years or older) and in 47% of preschool children (aged 0 to 5 years). Several genetic polymorphisms associated with iron status havebeen identified by using genome-wide association studies.

AIM

This study aimed to identify the functional polymorphismsrs855791 and rs2111833 in the transmembrane serine protease 6 (TMPRSS6) gene in female university students with IDA inthe Kingdom of Saudi Arabia.

METHODS

About 108 female students, aged from 18 to 25 years, were randomly selected and included to this study. Fifty-eightparticipants were iron deficient, and fifty participants were healthy. Blood samples were collected from all participants andassessed based on theirhaematologicaland biochemical iron status indices. Genotyping was carried out byusing PCR.

RESULTS

The genotype distribution oftheTMPRSS6rs855791 region in female studentsfromTabuk University,northern Saudi Arabia,was0% (CC), 77.6% (CT) and 22.4% (TT) in the iron-deficient students compared to 2% (CC), 96% (CT) and 2% (TT) in the healthy students,indicating significant differences in the allelic distribution betweentheiron-deficient group andthehealthy group. The genotype distribution of theTMPRSS6rs2111833 polymorphism was 8.6% (GG), 89.7% (GA) and 1.7% (AA) inthe iron-deficient students compared to 6% (GG), 92% (GA) and 2% (AA) in the healthy students,respectively,showing no differences between the iron-deficient group andthehealthy group in allelic distribution.

CONCLUSION

Our data demonstrated that theTMPRSS6 polymorphism rs855791 is significantly associated with decreased iron status, whereasTMPRSS6 polymorphismrs2111833 is not linked with iron deficiency status in female university students innorthern Saudi Arabia.

Donor Deferral Due to Low Hemoglobin-An Updated Systematic Review

Blood donors attending a donation session may be deferred from donating blood due to a failure to meet low hemoglobin (Hb) thresholds. This costs the blood donor service and donors valuable time and resources. In addition, donors who are deferred may have more symptoms, and as a direct and/or indirect effect of their experience, return rates of donors deferred for low Hb are reduced, even in repeat donors. It is therefore vital that low Hb deferral (LHD) is minimized. The aim of this updated systematic review is to expand the evidence base for factors which affect a donor's risk of deferral due to low Hb. Studies were identified by searching MEDLINE, Embase, The Cochrane Library, and the WHO International Clinical Trials Registry to March 2019. Demographic data, donor history, hematological/biological factors, and the primary outcome of deferral due to low Hb were extracted. Our primary outcome was deferral due to low Hb. Analyses were descriptive and quantitative; pooled odds ratios (ORs) and 95% confidence intervals (CIs) were obtained by meta-analysis using random-effects models. A total of 116 studies met the inclusion criteria. Meta-analysis showed a significantly greater risk of LHD in females compared with males in studies applying universal Hb thresholds for males and females (OR 14.62 95% CI 12.43-17.19) and in those which used sex-specific thresholds (OR 5.73, 95% CI 4.36-7.53). Higher rates of LHD were also associated with increasing age in men, low body weight, shorter interdonation interval, donors of Hispanic or African descent, higher ambient temperature, donors with low ferritin levels, and donation in a fixed donor center. There was conflicting evidence on the effect of new and repeat donor status, and blood group. This work has strengthened the evidence of the previous review in identifying factors that should be considered in studies of donor deferral and highlighting areas in need of further study, including ABO and Rh blood groups, previous platelet donation, diet, smoking, time of day, and genetic data. These factors may lead to individually tailored donation criteria for safe and efficient donation in the future.

The Association of TMPRSS6 Gene Polymorphism and Iron Intake with Iron Status among Under-Two-Year-Old Children in Lombok, Indonesia

Multiple common variants in transmembrane protease serine 6 (TMPRSS6) were associated with the plasma iron concentration in genome-wide association studies, but their effect in young children where anemia and iron deficiency (ID) were prevalent has not been reported, particularly taking account of iron intake. This study aims to investigate whether TMPRSS6 SNPs (rs855791 and rs4820268) and iron intake are associated with a low iron and hemoglobin concentration in under-two-year-old children. The study analyzed the baseline of a randomized trial (NUPICO, ClinicalTrials.gov NCT01504633) in East Lombok, Indonesia. Children aged 6–17 months (n = 121) were included in this study. The multiple linear regressions showed that TMPRSS6 decreased serum ferritin (SF) by 4.50 g/L per copy minor allele (A) of rs855791 (p = 0.08) and by 5.00 μg/L per copy minor allele (G) of rs4820268 (p = 0.044). There were no associations between rs855791 and rs4820268 with soluble transferrin receptor (sTfR) and hemoglobin (Hb) concentration (rs855791; p = 0.38 and p = 0.13, rs4820268; p = 0.17 and p = 0.33). The finding suggests the need for further studies to explore whether the nutrient recommendation for iron should be based on genetic characteristics, particularly for children who have mutation in TMPRSS6.

A child with severe iron-deficiency anemia and a complex TMPRSS6 genotype

OBJECTIVES

We report a case of a 7-year-old girl with severe hypochromic microcytic anemia, who was unresponsive to classical iron supplements. We suspected IRIDA, iron-refractory iron-deficiency anemia, a genetic iron metabolism disorder, caused by TMPRSS6 variations. TMPRSS6 encodes matriptase-2, a negative regulator of hepcidin, and its pathological variants are related to normal to high levels of hepcidin. We analyzed the TMPRSS6 gene and we improved clinical management of the patient, selecting the appropriate supplementation therapy. Intervention & Technique: The parenteral iron therapy was started, but the patient was only partially responsive and the anemia persisted. To confirm the diagnosis, the TMPRSS6 gene sequence was analyzed by DNA sequencing and other relevant biochemical parameters were evaluated.

RESULTS

The TMPRSS6 sequence analysis showed a complex genotype with a rare heterozygous missense variant, in addition to other common polymorphisms. The serum hepcidin value was normal. We unexpectedly observed a normalization of patient's hemoglobin (Hb) levels only after liposomal iron treatment.

DISCUSSION AND CONCLUSION

The proband was symptomatic for IRIDA during a critical phase of growth and development, but we did not find a clearly causative genotype. A long-term result, improving stably patient's Hb levels, was obtained only after liposomal iron supplementation. Children may be at greater risk for iron deficiency and the degree of anemia as well as the response to the iron supplements varies markedly patient to patient. Here, we show the importance of comprehensive study of these patients in order to collect useful information about genotype-phenotype association of genes involved in iron metabolism.

New insights into iron deficiency and iron deficiency anemia

Recent advances in iron metabolism have stimulated new interest in iron deficiency (ID) and its anemia (IDA), common conditions worldwide. Absolute ID/IDA, i.e. the decrease of total body iron, is easily diagnosed based on decreased levels of serum ferritin and transferrin saturation. Relative lack of iron in specific organs/tissues, and IDA in the context of inflammatory disorders, are diagnosed based on arbitrary cut offs of ferritin and transferrin saturation and/or marker combination (as the soluble transferrin receptor/ferritin index) in an appropriate clinical context. Most ID patients are candidate to traditional treatment with oral iron salts, while high hepcidin levels block their absorption in inflammatory disorders. New iron preparations and new treatment modalities are available: high-dose intravenous iron compounds are becoming popular and indications to their use are increasing, although long-term side effects remain to be evaluated.

Multiple sclerosis-like diagnosis as a complication of previously treated malaria in an iron and vitamin D deficient Nigerian patient

In contrast to malaria, multiple sclerosis (MS) is infrequently found in Black Africans. We describe a 29 year old Nigerian female who developed an MS-like condition with symptoms similar to relapsing-remitting MS following malaria infection, leading to a diagnosis of MS. However, absence of hyperintense lesions in the brain and spinal cord presented a conundrum since not all the diagnostic criteria for MS were met. Pathology supported genetic testing (PSGT) was applied to combine family and personal medical history, lifestyle factors, and biochemical test results for interpretation of genetic findings. This approach provides a means of identifying risk factors for different subtypes of demyelinating disease. The patient was subsequently treated according to an individualised intervention program including nutritional supplementation as well as a change in diet and lifestyle. Deficiencies of vitamin B12, iron and vitamin D were addressed. Genetic analysis revealed absence of the HLA DRB1*1501 allele, considered to be the most prominent genetic risk factor for MS. Extended mutation analysis identified variations in three genes in the folate-vitamin B12 metabolic pathway, which could have increased the patient's sensitivity to the antifolate drugs used to treat the malaria. A glutathione-S-transferase GSTM1 null allele, previously associated with neurological complications of malaria, was also detected. Furthermore, a heterozygous variation in the iron-related transmembrane protease serine 6 (TMPRSS6) gene, rs855791 was found, which could have impacted the patient's iron status following two successive blood donations and exposure to malaria preceding the MS diagnosis. PSGT identifies relevant risk factors for demyelinating disorders resembling MS and uses the data for individualised treatment programs, and to systematically build a database that can provide evidence in large patient cohorts. Follow-up investigations may be suggested, such as whole exome sequencing in selected cases, to ensure that remyelination and restoration of function are achieved.

Common Variants and Haplotypes in the TF, TNF-α, and TMPRSS6 Genes Are Associated with Iron Status in a Female Black South African Population

BACKGROUND

It is unknown whether single nucleotide polymorphisms (SNPs), associated with iron status in European and Asian populations, have the same relation within the African population.

OBJECTIVES

We investigated associations of reported SNPs with iron markers in a South African cohort.

METHODS

Hemoglobin concentration, serum ferritin (SF) and soluble transferrin receptor (sTfR) concentrations, and body iron (BI) stores were measured in women (n = 686; range, 32-86 y) who were part of the Prospective Urban and Rural Epidemiology study. Thirty-two SNPs in 12 genes were selected based on existing genome-wide association study data.

RESULTS

In the transferrin (TF) gene, SF and BI were significantly lower in the heterozygote genotype (AG) of reference SNP (rs) 1799852 (P = 0.01 and 0.03, respectively) and sTfR concentrations were significantly higher (P = 0.004) than the homozygote minor allele genotype (AA), whereas transferrin receptor and BI concentrations were significantly lower in the heterozygote genotype (AG) of rs3811647 (both P = 0.03) than the homozygote wild-type (AA) and minor allele groups (GG). The chromosome 6 allele combination (AAA) consisting of rs1799964 and rs1800629 both in tumor necrosis factor-α (TNF-α) and rs2071592 in nuclear factor κB inhibitor-like protein 1 (NFKBIL1) was associated with higher odds for low SF concentrations (SF < 15 μg/L; OR: 1.86; 95% CI: 1.23, 2.79) than the allele combinations AGA, GGT, and AGT. The chromosome 22 allele combination (GG) consisting of rs228918 and rs228921 in the transmembrane protease serine 6 (TMPRSS6) gene was associated with lower odds for increased sTfR concentrations (sTfR > 8.3mg/L; OR: 0.79; 95% CI: 0.63, 0.98) than the allele combination AA.

CONCLUSIONS

Various SNPs and allele combinations in the TF, TNF-α, and TMPRSS6 genes are associated with iron status in black South African women; however, these association patterns are different compared with European ancestry populations. This stresses the need for population-specific genomic data.

Iron deficiency: new insights into diagnosis and treatment

Iron deficiency and iron deficiency anemia are common conditions worldwide affecting especially children and young women. In developing countries, iron deficiency is caused by poor iron intake and/or parasitic infection, whereas vegetarian dietary choices, poor iron absorption, and chronic blood loss are common causes in high-income countries. Erythropoiesis stimulating agents can result in functional iron deficiency for erythropoiesis even when stores are iron-replete. Diagnosis of iron deficiency is straightforward, except when it occurs in the context of inflammatory disorders. Oral iron salts correct absolute iron deficiency in most patients, because low hepcidin levels facilitate iron absorption. Unfortunately frequent side effects limit oral iron efficacy. Intravenous iron is increasingly utilized, because currently available preparations allow rapid normalization of total body iron even with a single infusion and are effective also in functional iron deficiency and in iron deficiency associated with inflammatory disorders. The evidence is accumulating that these preparations are safe and effective. However, long-term safety issues of high doses of iron need to be further explored.