Juvenile hemochromatosis due to G320V/Q116X compound heterozygosity of hemojuvelin in an Irish patient

Hemojuvelin (HJV) is a recently discovered gene responsible for 1q-linked juvenile hemochromatosis. The majority of mutations characterized in this gene are rare and private, except G320V, identified in patients from different countries. Here, we report the clinical features and the molecular study of a young Irish patient presenting with severe cardiac disease related to iron overload. We sequenced the coding region and the exon-intron boundaries of genes associated with juvenile hemochromatosis, HAMP and HJV encoding hepcidin and hemojuvelin respectively. Two heterozygous HJV mutations were identified: the G320V mutation and the new Q116X mutation that cause a premature stop codon in the protein. This finding increases the number of mutations identified in HJV gene and underlines that the G320V is a recurrent mutation, even in Northern Europe.     

Three patients with middle-age-onset hemochromatosis caused by novel mutations in the hemojuvelin gene

Hemochromatosis is a genetically heterogeneous condition. Mutations in the recently described hemojuvelin gene were found in patients with juvenile hemochromatosis, who usually manifest clinical signs of iron overload, including cardiomyopathy and hypogonadism, in their teens and early 20s. In this report, we describe three Japanese patients who showed typical clinical and hepatic histological damage compatible with hemochromatosis at around 50 years of age. Genetic analyses showed that all three patients carried mutations in the hemojuvelin gene. The first patient was homozygous for a novel mutation (745G > C [D249H]), and the second and third patients from the same family were homozygous for another novel mutation (934C > T [Q312X]). No mutations in their HFE, hepcidin, transferrin receptor 2, or ferroportin genes were found. One patient had chronic infection with Helicobacter pylori. The age at initial presentation of hemojuvelin-hemochromatosis occurs over a wider range than previously described.     

Acute liver failure caused by concurrent autoimmune hepatitis and hepatitis B in a 16-year old girl

A 16 year-old girl was admitted to hospital because of fatigue and somnolence, nausea, epistaxis and jaundice. Physical examination revealed jaundice, an enlarged liver and tenderness of upper right abdomen. Laboratory tests revealed an increased level of acute liver failure, bilirubin, bile acids, GGTP and a decreased prothrombin ratio, with elevated gamma-globulin and IgG levels, and the presence of anti-mitochondrial M2 antibodies and HBV infection markers. The patient was diagnosed with liver failure resulting from chronic hepatitis B with an autoimmune component. The treatment consisted of steroids, azathioprine, vitamin K, low-protein diet and lactulose enemas. After undergoing a molecular test (HBV DNA 3.23 × 10(5) IU/mL and mutations I 204 and I 80), the treatment was modified by adding entecavir. After one month the patient was discharged in good clinical condition, with the recommendation of continued entecavir, prednisone and azathioprine. In subsequent months, no clinical deterioration or abnormal biochemical liver function test results were found, despite the discontinuation of immunosuppressive therapy after 10 mo. The patient continues entecavir therapy.     

Phenotypic expression of a novel C282Y/R226G compound heterozygous state in HFE hemochromatosis: Molecular dynamics and biochemical studies

Most adults affected with hereditary hemochromatosis are homozygous for a single point mutation of HFE (p.Cys282Tyr). Apart from the compound heterozygous state for the p.Cys282Tyr mutant and the widespread p.His63Asp variant allele, other rare HFE mutations can be found in trans and may have clinical impact. In the present report we describe the structural and functional consequences of a new mutation, namely the p.Arg226Gly which was inherited in trans with the p.Cys282Tyr allele in a patient affected with a mild iron overload. Because the R226G substitution is located in the vicinity of the normal Cys225S–S282Cys disulfide bond we initially investigated the structure of the variant by molecular dynamics techniques in order to estimate the effect of the mutation on the global structure of HFE domain α3. We found that the solvation free energy, hydrophobicity and formation of salt bridges are slightly modified with the global secondary structure of the α3 domain being conserved. In a previous paper, we demonstrated that the Q283P substitution leads to the loss of the normal Cys225S–S282Cys disulfide bridge. Similar to the Q283P substitution, the R226G substitution does not substitute a residue directly involved in the formation of the disulfide bridge. However, unlike the p.Gln283Pro variant which destroyed the normal disulfide bridge, the R226G mutation does not affect the normal Cys225S–S282Cys bridge. Furthermore based on cell line studies we clearly show that the mutation does not prevent cell surface localization, β2-microglobulin association and binding to transferrin receptor 1. This new compound heterozygous phenotype is very close to those of the C282Y/H63D compound heterozygous patients who display the biochemical hemochromatosis phenotype but with lower body iron stores than C282Y homozygotes. Our results do not exclude unknown genetic and/or metabolic factors that may act synergistically to increase the ferritin level.     

Complete heart block in a 9 year old girl caused by borreliosis.

A complete atrioventricular block was seen in a nine year old girl in whom an infection with Borrelia burgdorferi was confirmed by serological testing. There were no other symptoms or cutaneous manifestations of the disease. Though a rash on the right ear was later recalled by her parents. The patient was treated with high dose penicillin and orciprenaline was given intermittently. The complete heart block disappeared within four days.     

Prevalence of the G320V mutation of the HJV gene, associated with juvenile hemochromatosis, in Greece

Mutations of the HJV gene, which maps on chromosome 1q21, underlie most cases of juvenile hemochromatosis. We evaluated the frequency of the most common mutation (G320V) of the HJV gene in the Greek population, since 50% of cases of hereditary hemochromatosis in Greece carry mutations of the HJV gene.     

Screening hepcidin for mutations in juvenile hemochromatosis: identification of a new mutation (C70R)

Juvenile or type 2 hemochromatosis (JH) is a genetic disease caused by increased intestinal iron absorption that leads to early massive iron overload. The main form of the disease is caused by mutations in a still unknown gene on chromosome 1q. Recently, we recognized a second type of JH with clinical features identical to the 1q-linked form, caused by mutations in the gene encoding hepcidin (HEPC). Hepcidin is a hepatic antimicrobial-like peptide whose role in iron homeostasis was first defined in animal models; deficiency of hepcidin in mice leads to iron overload, whereas its hepatic overexpression in transgenic animals causes iron deficiency. To define the prevalence of HEPC mutations in JH we screened the HEPC gene for mutation in 21 unrelated JH subjects. We identified a new mutation (C70R), which affects 1 of the 8 conserved cysteines that form the disulfide bonds and are critical for the stability of the polypeptide.     

Two novel missense mutations of the HFE gene (I105T and G93R) and identification of the S65C mutation in Alabama hemochromatosis probands

Sequencing of HFE exons 2, 3, 4, and 5, and of portions of introns 2, 4, and 5 revealed novel mutations in four of twenty hemochromatosis probands who lacked C282Y homozygosity, C282Y/H63D compound heterozygosity, or H63D homozygosity. Probands 1 and 2 were heterozygous for previously undescribed mutations: exon 2, nt 314T-->C (314C; I105T), and exon 2, nt 277G-->(277C; G93R), respectively; these probands were also heterozygous for H63D and C282Y, respectively. Probands 3 and 4 were heterozygous for a previously described but uncommon HFE mutation: exon 2, nt 193A-->T (193T; S65C). Proband 3 was also heterozygous for C282Y and had porphyria cutanea tarda, and Proband 4 had hereditary stomatocytosis. Each of these four probands had iron overload. In each proband with an uncommon HFE coding region mutation, I105T, G93R, and S65C occurred on separate chromosomes from those with the C282Y or H63D mutations. Neither I105T, G93R, nor S65C occurred as spontaneous mutations in our probands. The I105T and G93R mutations were linked to haplotypes bearing HLA-A3,-B7 and HLA-A2,-B62, respectively. The S65C mutation was linked to a haplotype characterized by HLA-32. Sixteen other probands did not have an uncommon HFE exon mutation. In 176 normal control subjects, two were heterozygous for S65C, but I105T and G93R were not detected. Nine of twenty probands were heterozygous and two probands were homozygous for a previously described base-pair change at intron 2, nt 3671T-->C. One proband without a detectable missense mutation had a previously described intron 5 allele (nt 6700G-->A). Heterozygosity for a previously described base-pair change in intron 4 (nt 5636T-->C) was detected in all persons we studied who also had the S65C mutation. One proband was heterozygous for a previously undescribed base-pair change at intron 5 (nt 5807A-->G). We conclude that uncommon HFE exon and intron mutations may be discovered among hemochromatosis patients who have "atypical" HFE genotypes.     

Plasminogen Kanagawa-I, a novel missense mutation, is caused by the amino acid substitution G732R

A new dysplasminogen, plasminogen Kanagawa-I, was identified in a healthy male with no previous thrombotic episodes. His plasma plasminogen (PLG) activity was 51.4% of that of normal pooled plasma (reference interval 70–130%) and the antigen level was 94.2% of that of normal pooled plasma (reference interval 80–150%). Nucleotide sequencing revealed a heterozygous G to A transition in exon 18, which resulted in an amino acid substitution of G732R. Both the proband's father and paternal grandfather were heterozygous for this mutation. Interestingly, the grandfather was found to be a compound heterozygote for plasminogen Kanagawa-I and Tochigi (A601T), so that his plasminogen activity and antigen level was 7.7% and 87.2% of that of normal pooled plasma, respectively. However, he has never been affected by significant thrombosis.     

Identification of four novel mutations in F5 associated with congenital factor V deficiency

Coagulation factor V (FV) deficiency is a rare bleeding disorder characterized by low coagulant and antigen levels of FV with bleeding symptoms ranging from mild to severe. Only a limited number of mutations have been reported because of the large size of the factor V gene (F5) as well as the low prevalence. In this study, we have identified four novel mutations in F5 in five unrelated patients with congenital FV deficiency. All the patients, including two with undetectable FV activity, were asymptomatic and were found to have prolonged prothrombin time and activated partial thromboplastin time during preoperative screening or routine examinations. All four mutations found in this study are either missense or in-frame deletion. This is in contrast with previous reports of a high frequency of mutations introducing premature termination codons in inherited FV deficiency. Missense mutations of F5 might produce a mild phenotype and are not frequently diagnosed. Although FV deficiency is a very rare disorder with a predicted incidence of one in 1 million, this study suggests that the numbers of F5 mutations, especially missense mutations, are higher than estimated.     

Characterization of the mutations in the glucose-6-phosphatase gene in Israeli patients with glycogen storage disease type 1a: R83C in six Jews and a novel V166G mutation in a Muslim Arab

Summary Glycogen storage disease type 1a (GSD 1a), an autosomal recessive disease, is caused by the inactivity of glucose-6-phosphatase, the gene of which has been recently cloned. We report on the missense mutation C T at nucleotide 326 of the G6Pase gene, causing the change of the Arg codon at position 83 into a Cys codon, as the single mutation detected in six Jewish patients. This finding suggests that this mutation might be prevalent among the Jewish population. A new missense mutation T G at nucleotide 576 resulting in V166G was found in an Arab Muslim patient. These families may benefit now from pre- and postnatal diagnosis by analysis of DNA from blood and amniotic fluid or chorionic villus cells rather than liver biopsy. No mutations in the G6Pase gene were detected in two GSD 1b patients.     

Severe coagulation factor V deficiency caused by 2 novel frameshift mutations: 2952delT in exon 13 and 5493insG in exon 16 of factor 5 gene.

A male infant with severe bleeding tendency had undetectable factor V activity. Sequence analysis of the proband's DNA revealed one base deletion in exon 13 (2952delT) and one base insertion in exon 16 (5493insG) in heterozygous form. Both mutations introduced a frameshift and a premature stop at codons 930 and 1776, respectively. The proband's father and mother were heterozygous for 2952delT and for 5493insG, respectively. Both mutations would result in the synthesis of truncated proteins lacking complete light chain or its C-terminal part. In the patient's plasma, no factor V light chain was detected by enzyme-linked immunosorbent assay. The N-terminal portion of factor V containing the heavy chain, and the connecting B domain was severely reduced but detectable (1.7%). A small amount of truncated factor V-specific protein with a molecular weight ratio of 236 kd could be immunoprecipitated from the plasma and detected by Western blotting. This protein, factor V(Debrecen), corresponds to the translated product of exon 16 mutant allele.     

Severe congenital factor XIII deficiency caused by novel W187X and G273V mutations in the F13A gene; diagnosis and classification according to the ISTH/SSC guidelines

Factor XIII (FXIII) consists of the A and B subunits (FXIII‐A and FXIII‐B) and stabilizes fibrin clots. Defects in either the FXIII‐A or FXIII‐B gene lead to congenital FXIII deficiency, which manifests a life‐long haemorrhagic tendency. Thus, prophylactic FXIII replacement therapy is recommended. To establish a management plan for a 30‐year‐old male patient with ‘indefinite’ FXIII deficiency (<40% of the normal FXIII), he was characterized by state‐of‐the‐art techniques as guided by the FXIII/Fibrinogen subcommittee of ISTH/SSC. FXIII activity turned out to be virtually undetectable by three functional assays. Four immunological assays detected essentially no FXIII protein, FXIII‐A antigen, and A₂B₂ antigen, but normal FXIII‐B antigen. Accordingly, he was diagnosed as a ‘severe’ FXIII‐A deficiency case. He had no anti‐FXIII antibodies, because a 1:1 cross‐mixing test (ammonia release assay) and a five‐step mixing test (amine incorporation assay) between his plasma and normal plasma demonstrated deficiency patterns. Furthermore, a dosing test using plasma‐derived FXIII concentrates revealed its normal recovery. DNA sequencing analysis identified two novel mutations, W187X & G273V , in the F13A gene. Genetic analyses confirmed that he was a compound heterozygote and his mother and sister were heterozygotes of either one of these mutations, indicating the hereditary nature of this disorder. Molecular modelling predicted that the G273V mutation would cause clashes with the surrounding residues in the core domain of FXIII‐A, and ultimately would result in the instability of the mutant molecule. Detailed characterization of ‘indefinite’ FXIII deficiency made it possible to make its definite diagnosis and best management plan.