A Portuguese patient homozygous for the -25G>A mutation of the HAMP promoter shows evidence of steady-state transcription but fails to up-regulate hepcidin levels by iron

Abstract

patients with thrombosis tested antibody positive, compared with 26 (6.1%) of 425 patients without thrombosis (odds ratio [OR], 15.3 [95% CI,]; P ϭ .005). This supports previous suggestions 6 that formation of platelet-activating HIT antibodies can be associated with thrombosis even in the absence of a significant platelet count fall. Second, among the 87.7% of study patients who underwent serologic testing for HIT antibodies, there was approximately a 60% lower seroconversion rate with LMWH compared with UFH (55.6% and 64.7% by the platelet activation assay and immunoassay, respectively). Nevertheless, despite this moderate reduction in frequency of HIT antibody formation, there was complete avoidance of clinical HIT using LMWH (0 versus 12 cases). This underscores the importance of considering HIT to be a largely preventable adverse drug reaction, at least in postorthopedic surgery patients. To the editor:A Portuguese patient homozygous for the ؊25G>A mutation of the HAMP promoter shows evidence of steady-state transcription but fails to up-regulate hepcidin levels by ironMutations of hepcidin are a rare cause of juvenile hemochromatosis (JH). We report a homozygous Ϫ25GϾA mutation in the hepcidin 5Ј untranslated region (UTR) that generates a new start codon with a consequent frameshift. In this patient with a rare coincidental association of JH, Turner syndrome, and absolute lymphopenia, the absence of normal hepcidin synthesis was expected. Surprisingly, the patient had detectable hepcidin, suggesting that the start of translation was maintained at the original ATG with some normal protein production. However, hepcidin was not appropriately induced by an iron challenge test, supporting role of hepcidin on the clinical expression of iron overload in this case. The hepatic peptide hepcidin is a key regulator of iron balance. 1 Mutations of hepcidin are a rare cause of juvenile hemochromatosis (JH), 2-3 and include nonsense, frameshift, 2 and missense mutations C70R and C78T affecting conserved cysteines. [3][4][5] Recently a Ϫ25GϾA mutation in the HAMP 5ЈUTR was described in 2 Portuguese siblings with iron overload and absence of urinary hepcidin. 6 Here, the same mutation was found in a different Portuguese family where the proband shows coincidental association of JH, Turner syndrome, and absolute lymphopenia. 7 Although no comparative haplotype analysis was performed, geographic and historical tracking does not indicate any relationship with the previously described family. In the proband, no mutations in the coding regions of HAMP and hemojuvelin genes were found by sequencing. 3,8 However, in the 5ЈUTR region of HAMP, a GϾA point mutation was identified at position Ϫ25 from the canonical ATG. This was confirmed by WAVE (Transgenomic, Omaha, NE) denaturing high-performance liquid chromatography (DHPLC; heteroduplexes were formed by heat denaturation at 94°C for 3 minutes and cooling to 25°C for 45 minutes; the mixture was analyzed at a melting temperature of 64.1°C, with a linear acetonitrile gradient:...

A new mutation in the hepcidin promoter impairs its BMP response and contributes to a severe phenotype in HFE related hemochromatosis

“…7,8 The molecular mechanisms linking the p.Cys282Tyr mutation and low hepcidin levels are not fully characterized. Mutations in other genes, including transferrin receptor 2 (TFR2), hemojuvelin (HJV) and ferroportin (FPN), 9,10 as well as in coding and non-coding regions of hepcidin (HAMP), [11][12][13] are known to induce phenotypic presentations similar to HFE related GH. HFE related GH is a disease with incomplete penetrance.…”

Non-classical hereditary hemochromatosis in Portugal: novel mutations identified in iron metabolism-related genes

“…This mutation creates a new initiation codon at position +14 related to the cap site, which induces a shift of the open reading frame. Homozygosity for this mutation was previously reported as the cause of JH in two other individuals of Portuguese origin [31,37]. As this third affected individual had a birth place located near the first one described (Matthes T, personal communication), probably they are related to the same HAMP mutational event.…”

Next-generation sequencing of hereditary hemochromatosis-related genes: Novel likely pathogenic variants found in the Portuguese population

“…The first two cases of JH due to homozygosity for this mutation were reported by Matthes and co-workers [12] in two Portuguese siblings. Then, another two JH patients were reported, also presenting homozygosity for the same mutation, in two unrelated families of North [13] and Centre of Portugal [8]. In this study, we report another two Portuguese siblings, with JH phenotype and homozygosity for the same mutation.…”

“…Thirteen out of the mentioned 53 different identified variants were absent from the public databases (Table I). One of them, the HAMP (c.-25GNA), although not annotated in databases had been already found in the Portuguese population [8,12,13], and was considered a private variant. Among these 13 novel/private variants, five were predicted to be pathogenic by in silico studies and by genotype/phenotype correlation: three are missense mutations in HFE (p.Tyr 230Cys), and TFR2 (p.Leu750Pro and p.Ala777Val); one is a splicing mutation in TFR2 gene (c.967-1GNC); and one is located at the 5′-UTR of the HAMP gene (c.-25GN A).…”