Hereditary hyperferritinaemia-cataract syndrome: a challenging diagnosis for the hepatogastroenterologist

Hereditary hyperferritinaemia-cataract syndrome (HHCS) is a relatively rare disorder with an autosomal dominant trait. It can be caused by various mutations within the iron responsive element (IRE) of the L-ferritin gene. These mutations result in an increased translation of L-ferritin mRNA and consequently the accumulation of L-ferritin in different fluids and tissues. HHCS patients present with an isolated hyperferritinaemia in the absence of any sign of iron overload. Early onset bilateral cataract, probably due to accumulation of ferritin crystals in the lens, is the only presenting clinical manifestation. Internists, especially gastrohepatologists, should be aware of this syndrome and differentiate it from haemochromatosis which is much more frequent, in order to avoid unnecessary imaging procedures, liver biopsies and an eventual venesection therapy, which will only lead to microcytic anaemia. In the present paper we report the first cases with HHCS diagnosed in Belgium. At diagnosis, the seven known affected members of three different families had ferritin levels between 603 and 3432 microg/l (normal < 150 microg/l), and this in combination with normal iron and transferrin values. All of them were known with early-onset bilateral cataract and our postulated diagnosis of HHCS was confirmed after genetic sequencing of the L-ferritin gene, which showed a C39U point mutation in the first family, and an A40G point mutation in the IRE loop segment in the two other families. The other investigated members of the three families had normal ferritin values, no history of early-onset cataract and genetic analyses could not reveal a mutation in the IRE of their L-ferritin gene. In current clinical practice, gastroenterologists should remember that elevated ferritin levels in the absence of documented iron overload is not haemochromatosis.     

Pathogenesis of hyperferritinemia cataract syndrome

Hereditary hyperferritinemia-cataract syndrome (HHCS) is an autosomal dominant disorder characterized by bilateral cataracts and increased serum L-ferritin, in the absence of iron overload. Under physiological conditions, ferritin synthesis is finely regulated at the translational level by iron availability. This regulation is achieved by the high-affinity interaction between cytoplasmic mRNA-binding proteins (iron regulatory proteins, IRPs), and mRNA stem-loop structures, known as iron responsive elements (IREs), located in the untranslated regions (UTRs) of the mRNAs. A single IRE is located on the 5' UTR of a series of genes involved in iron metabolism, like L-ferritin, and the binding IRE-IRPs represses these genes translation. The deregulation of ferritin production responsible of HHCS is caused by heterogeneous mutations in the iron regulatory element (IRE) of L-ferritin that interfere with the binding of iron regulatory proteins, disrupting the negative control of L-ferritin synthesis and causing the constitutive up-regulation of ferritin L-chains. The HHCS families originate from different countries of Europe and North America, suggesting that HHCS may be distributed widely throughout the world and not sporadic, whereas its prevalence remains to be established. The lens seems to be particularly sensitive to the increased amount of L-ferritin and the alteration of the proteic equilibrium in this tissue can be responsible of the cataract. In spite of the elucidation of the genetic basis, the genotype phenotype correlation is not clear. Recently, a study based on the thermo-denaturation profile and dissociation constant of the IRE-IRP complex performed for several mutated IREs has provided evidence for a possible correlation between heterogeneous IRE mutations and serum ferritin levels. On the other hand, the in vivo relevance of these conclusions has not been determined completely. A clinical variability among subjects sharing the same mutation, whether they belonged to the same family or not, has also been demonstrated. These findings suggest that, besides the L-ferritin IRE genotype, additional factors are likely to modulate the lens involvement and the rate of progression to severe cataract in HHCS patients.     

Hereditary hyperferritinemia-cataract syndrome (HHCS) presenting with iron deficiency anemia associated with a new mutation in the iron responsive element of the L ferritin gene in a Swiss family

Hereditary hyperferritinemia-cataract syndrome (HHCS) is one of the differential diagnoses of hyperferritinemia (HF) with low or normal transferrin saturation but is usually not associated with anemia. Here, we report a case of a microcytic, hypochromic anemia with hyperferritinemia as the initial presentation of a combination of iron deficiency anemia and HHCS. The latter is an autosomal dominant disorder characterized by distinctive cataracts and HF in the absence of iron overload. Sequencing studies were carried out to look for mutations in the iron responsive element (IRE) of the L ferritin gene. A heterozygous single point mutation for a +24T to C substitution in the IRE of the L ferritin gene (=HGVS c.-176T>C) was detected which has not been described before. To evaluate the pathogenetic relevance of this new mutation, we performed family studies of parents and siblings. We could identify the father and one brother with HF, cataract, and the heterozygous +24T>C mutation. Neither the mother nor the five other siblings had HF, cataract or that mutation. We therefore conclude that this newly described heterozygous +24T>C mutation in the IRE of the L ferritin gene causes HHCS.     

Hereditary hyperferritinemia cataract syndrome in three unrelated families of western Greek origin caused by the C39 > G mutation of L-ferritin IRE

Hereditary hyperferritinemia-cataract syndrome (HHCS) is a well-characterized autosomal dominant disease caused by mutations in the iron responsive element (IRE) of ferritin L-chain (FTL) mRNA. Mutations in the IRE result in reduced binding of the trans-acting iron regulatory proteins (IRPs) and hence in upregulation of ferritin L-chain synthesis. The disease is characterized by increased L-ferritin in serum and tissues and early onset of bilateral cataracts. Iron metabolism is normal, and there is no tissue iron overload. At least 25 nucleotide substitutions and deletions in the L-ferritin IRE have been described in families with HHCS, originating from diverse European, Australian and North American populations. We studied the molecular pathogenesis of HHCS in three unrelated kinderships of western Greek origin, with 19 affected members. We identified a relatively rare C39G mutation located in the hexanucleotide loop of L-ferritin IRE. Computational analysis of mRNA folding of mutant FTL IRE predicted that the C39 > G mutation leads to a rearrangement of base pairing in this critical region, which is likely to modify the IRP binding affinity. All subjects with HHCS were heterozygotes for the same C39G mutation. Clinical and laboratory phenotypes were described. Moreover, there was evidence of an association between this FTL IRE stem-loop mutation and very high ferritin levels. Our findings broaden the list of populations where HHCS has been described.     

Two Dutch families with hereditary hyperferritinaemia-cataract syndrome and heterozygosity for an HFE-related haemochromatosis gene mutation

Hereditary haemochromatosis is an autosomal recessive disorder, leading to progressive iron overload, which is very common among the Caucasian population. In the vast majority of the cases, the hereditary iron overload is caused by mutations in the HFE gene. Most prominently this is the homozygous Cys282Tyr mutation. We report two Dutch families in which both propositi were found to be heterozygous for Cys282Tyr in the work-up of hyperferritinaemia. Frequent phlebotomies had no effect on the ferritin level, but led to microcytic anaemia. Finally, the family history with bilateral cataracts was the clue for the correct diagnosis. Hereditary hyperferritinaemia-cataract syndrome (HHCS) is an autosomal dominant disease characterised by elevated serum ferritin levels and bilateral cataracts in the absence of iron overload. Several point mutations and deletions within the iron-responsive element (IRE) in the 5' noncoding region of the L-ferritin gene have been found in HHCS families. In the first Dutch family a G to C transition at position 32 was found and a G to A mutation at the same location was found in the second Dutch family. In individuals with an isolated hyperferritinaemia (normal transferrin saturation), the presence of early onset (familial) cataract should raise the possibility of HHCS, even when Cys282Tyr heterozygosity is found.     

Recurrent mutations in the iron regulatory element of L-ferritin in hereditary hyperferritinemia-cataract syndrome.

BACKGROUND AND OBJECTIVE: Hereditary hyperferritinemia-cataract syndrome (HHCS) is an autosomal dominant disorder characterized by bilateral cataracts and increased serum and tissue L-ferritin, in the absence of iron overload. The deregulation of ferritin production is caused by heterogeneous mutations in the iron regulatory element (IRE) of L-ferritin that interfere with the binding of iron regulatory proteins. DESIGN AND METHODS: We have identified several patients from three unrelated Italian families with HHCS. Iron parameters were assessed by standard methods. The IRE element of L-ferritin was amplified by PCR using appropriate primers and directly sequenced. RESULTS: Ferritin levels ranged from 918 microg/L to 2490 microg/L in the patients studied. In one family bilateral cataracts were diagnosed early in life, whereas in the others cataracts were diagnosed around 40-50 years. The female proband of family 3 presented with a severe iron deficiency anemia, which was unrecognized because of the increased ferritin values. Sequencing of the IRE element of L-ferritin in the probands of the three families identified three different nucleotide substitutions (+32 GAE A, +40 AAE G and +39 CT) in the IRE of L-ferritin. These mutations have already been reported in unrelated subjects of different ethnic origins. INTERPRETATION AND CONCLUSIONS: Our findings are consistent with recurrent mutations associated with HHCS and underline the importance of this syndrome in the differential diagnosis of unexplained hyperferritinemia. In addition, the findings highlight the role played by transferrin saturation in the diagnosis of iron deficiency in these patients.     

A new mutation (G51C) in the iron-responsive element (IRE) of L-ferritin associated with hyperferritinaemia-cataract syndrome decreases the binding affinity of the mutated IRE for iron-regulatory proteins

Hereditary hyperferritinaemia-cataract syndrome is an autosomal dominant disorder characterized by a constitutively increased synthesis of L-ferritin in the absence of iron overload. The disorder is associated with point mutations in the iron-responsive element (IRE) of L-ferritin mRNA. We report a new mutation, G51C, identified in two members of a Canadian family, presenting a moderate increase in serum ferritin and a clinically silent bilateral cataract. Gel retardation assays showed that the binding of the mutated IRE to iron-regulatory proteins (IRPs) was reduced compared with the wild type. Structural modelling predicted that the G51C induces a rearrangement of base pairing at the lateral bulge of the IRE structure which is likely to modify IRE conformation.     

Molecular analyses of patients with hyperferritinemia and normal serum iron values reveal both L ferritin IRE and 3 new ferroportin (slc11A3) mutations

Unexplained hyperferritinemia is a common clinical finding, even in asymptomatic persons. When early onset bilateral cataracts are also present, the hereditary hyperferritinemia-cataract syndrome (HHCS), because of heterozygous point mutation in the L ferritin iron-responsive element (IRE) sequence, can be suspected. We sequenced the L ferritin exon 1 in 52 DNA samples from patients referred to us for molecular diagnosis of HHCS. We identified 24 samples with a point mutation/deletion in the IRE. For the 28 samples in which no IRE mutation was present, we also genotyped HFE mutations and sequenced both H ferritin and ferroportin genes. We found an increased frequency of His63Asp heterozygotes (12 of 28) but no H ferritin mutations. We identified 3 new ferroportin mutations, producing, respectively, Asp157Gly, Gln182His, and Gly323Val amino acid replacements, suggesting that these patients have dominant type 4 hemochromatosis. This study demonstrates that both L ferritin IRE and ferroportin mutations can account for isolated hyperferritinemia. The presence of cataract does not permit the unambiguous identification of patients with HHCS, although the existence of a family history of cataract was only encountered in these patients. This raises the intriguing possibility that lens ferritin accumulation might be a factor contributing to age-related cataract in the general population. Additional causes of isolated hyperferritinemia remain to be identified.     

Hyperferritinaemia in the absence of iron overload

Background—Serum ferritin is normally a marker ofiron overload. Ferritin genes are sited at chromosomes 19 and 11. Regulation of ferritin synthesis involves an interaction between aniron regulatory protein (IRP) and part of the ferritin mRNA designated the iron regulatory element (IRE). A disorder of ferritin synthesis resulting in hyperferritinaemia in the absence of iron overload hasbeen described recently.
Patients and methods—Hyperferriti- naemia in theabsence of iron overload was detected in a patient who was investigatedfor possible haemochromatosis. Serum iron, transferrin saturation, andferritin concentration were studied in 11 members of this patient'sfamily from three generations. Eight members had DNA samples analysedby direct cycle sequencing of the 5' untranslated region of the Lferritin gene.
Results—Six of the family members studied hadserum ferritin concentrations greater than 900 µg/l. However, serumiron and transferrin saturation were normal in these subjects who allhad evidence of cataracts. Three affected family members who hadgenetic studies of the L ferritin gene on chromosome 19 had an A to G point mutation which was not found in unaffected members.
Conclusions—There was complete concordance betweena mutated IRE, cataracts, and hyperferritinaemia in three generationsof this family. This family study confirms the finding that hereditary hyperferritinaemia in the absence of iron overload is an autosomal dominant inherited disorder.

     

Hereditary hyperferritinaemia/ cataract syndrome

In mammalian cells, cellular iron homeostasis is maintained by the co-ordinated regulation of transferrin receptor and ferritin synthesis that occurs at the translational level. This regulation is mediated by iron-responsive elements (IREs) that are found within the untranslated regions (UTRs) of mRNA and by cytoplasmic mRNA-binding proteins, known as iron regulatory proteins (IRPs). When cellular iron is scarce, IRPs are available for binding the 5' IRE of ferritin mRNA, initiation of translation is prevented and ferritin synthesis is inhibited. By contrast, the presence of abundant intracellular iron prevents binding of the IRPs to the 5' IRE and allows efficient mRNA translation to proceed. Hereditary hyperferritinaemia/cataract syndrome (HHCS) arises as a result of various point mutations or deletions within a protein binding sequence in the 5'-UTR of the L-ferritin mRNA, which results in increased efficiency of L-ferritin translation. Each unique mutation confers a characteristic degree of hyperferritinaemia and severity of cataract in affected individuals. This exemplifies a new paradigm in which mutations in mRNA cis-acting elements may be responsible for phenotypic variability in disease states.     

The evaluation of hyperferritinemia: an updated strategy based on advances in detecting genetic abnormalities

The number of new genes implicated in iron metabolism has dramatically increased during the last few years. Alterations of these genes may cause hyperferritinemia associated or not with iron overload. Correct assignment of the specific disorder of iron metabolism requires the identification of the causative gene mutation. Here, we propose a rational strategy that allows targeting the gene(s) to be screened for a diagnostic purpose. This strategy relies on the age of onset of the disease, the type of clinical symptoms, the biochemical profile (elevated or normal serum transferrin saturation (TfSat)), the presence or not of visceral iron excess, and the mode of inheritance (autosomal recessive or dominant). Then, two main entities can be differentiated: genetic (adult or juvenile) hemochromatosis characterized by elevated TfSat, and hereditary hyperferritinemias where TfSat is normal (or only slightly modified). Adult genetic hemochromatosis (GH) is related mainly to mutations of the HFE gene, and exceptionally to mutations of the TFR2 gene. Juvenile GH is a rare condition related principally to mutations of the HJV gene coding for hemojuvelin, and rarely to mutations of the HAMP gene coding for hepcidin. Hereditary hyperferritinemias are linked to mutations of three genes: the L-ferritin gene responsible for the hereditary hyperferritinemia cataract syndrome (without iron overload), the ferroportin gene leading to a dominant form of iron overload, and the ceruloplasmin (CP) gene corresponding to an iron overload syndrome with neurological symptoms. The proposed strategic approach may change with the identification of other genes involved in iron metabolism.     

Hereditary hyperferritinemia-cataract syndrome. Study of a new family in Spain.

The hyperferritinemia-cataract syndrome, inherited as a Mendelian dominant trait, is due to mutations in the 5' non-coding region of the ferritin light chain gene that modifies the shape of the IRE (iron responsive element) region, which loses its normal function of regulating the synthesis of ferritin light chains. Excess of light chains results in complexes that accumulate into the lens giving rise to early cataracts. We present a Spanish family with seven affected members through three generations. A genetic study reveals a substitution of a single base (C-->T) at position 33 in the IRE sequence in the index case and in one affected brother, whereas a non-affected sister shows the normal sequence. The hyperferritinemia-cataract syndrome was identified in 1995 and is still poorly understood. Clinicians should suspect it when treating any subject with early cataracts, even more if they are familial, or in patients with very high levels of ferritinemia without evidence of iron overload. There are no known consequences of the syndrome other than cataracts, and its proper diagnosis carries a favorable prognosis and eliminates the risk of unnecessary phlebotomies.     

Clinical, biochemical and molecular findings in a series of families with hereditary hyperferritinaemia–cataract syndrome

Hereditary hyperferritinaemia-cataract syndrome (HHCS) is an autosomal dominant disease caused by mutations in the iron responsive element (IRE) of the l-ferritin gene. Despite the elucidation of the genetic basis, the overall clinical spectrum of HHCS has been less well studied as, to date, only individual case reports have been described. Therefore, we studied a total of 62 patients in 14 unrelated families, with nine different mutations. No relevant symptoms other than visual impairment were found to be associated with the syndrome. A marked phenotypic variability was observed, particularly with regard to ocular involvement (i.e. age range at which cataract was diagnosed in 16 subjects with the C39T: 6-40 years). Similarly, serum ferritin levels varied substantially also within subjects sharing the same mutation (i.e. range for the A40G: 700-2412 microg/l). We followed an HHCS newborn in whom well-defined lens opacities were not detectable either at birth or at 1 year. The lens ferritin content was analysed in two subjects who underwent cataract surgery at different ages, with different cataract morphology. Values were similar and about 1500-fold higher than in controls. These observations suggest that: (i) in HHCS the cataract is not necessarily congenital; (ii) in addition to the IRE genotype, other genetic or environmental factors may modulate the phenotype, especially the severity of the cataract.     

Mutation spectrum in Australian pedigrees with hereditary hyperferritinaemia-cataract syndrome reveals novel and de novo mutations

Hereditary hyperferritinaemia-cataract syndrome (HHCS) (OMIM #600886) is a rare autosomal dominant condition identified by high serum ferritin levels with normal iron saturation and distinctive bilateral cataract. It may be misdiagnosed as haemochromatosis and such patients become anaemic as a result of inappropriate venesection. The elevated serum ferritin is due to a mutation in the iron-responsive element (IRE) of the l-ferritin gene, resulting in excessive l-ferritin production. We report the identification of three Australian pedigrees; one with a previously described mutation at position 40, a pedigree with a novel mutation at position 39 and an individual with a de novo mutation at position 32 of the l-ferritin IRE.     

A linkage between hereditary hyperferritinaemia not related to iron overload and autosomal dominant congenital cataract

Summary. The only genetic disorder with elevated serum ferritin levels so far described is hereditary HLA-related haemochromatosis. On the other hand, hereditary cataract is both genotypically as well as phenotypically heterogenous, and no specific locus or any useful marker has been yet identified. We studied two Italian families in whom a combination of elevated serum ferritin not related to iron overload and congenital nuclear cataract is transmitted as an autosomal dominant trait. Affected individuals have normal serum iron and transferrin saturation, but high serum ferritin. Red cell counts are normal and venesection therapy rapidly produces iron-deficiency anaemia.
This genetic disorder, which is characterized by hyperferritinaemia, differs from hereditary HLA-related haemochromatosis mostly for the absence of iron overload. A gene responsible for the congenital nuclear cataract likely maps on chromosome 19q close to the ferritin L-subunit gene. Within families with autosomal dominant congenital cataract, serum ferritin might be an early marker of disease.     

Role of ferritin and ferroportin genes in unexplained hyperferritinaemia

A large body of evidence indicates that the level of serum ferritin parallels the concentration of storage iron within the body, regardless of the cell type in which it is stored. Elevated serum ferritin levels, in the absence of inflammation and liver disease, are currently taken to indicate increased iron stores and require further investigation to determine the site of iron overload. Until recently, the only genetic disorder with elevated serum ferritin levels known in Western countries was hereditary HLA-related HFE-related genetic haemochromatosis in Caucasians (HFE, OMIM 235200), and a high serum ferritin in apparently healthy persons was considered suggestive of this disease. In the last few years, at least two novel genetic disorders of iron metabolism presenting as unexplained hyperferritinaemia have been recognized. The first one is hereditary hyperferritinaemia/cataract syndrome (HHCS, OMIM 600886). HHCS arises from various point mutations or deletions within a protein binding sequence in the 5'-UTR of the L-ferritin mRNA that results in increased efficiency of L-ferritin translation. The second one is haemochromatosis type 4, or HFE4 (OMIM 606069), or ferroportin disease. In this latter condition, reticuloendothelial iron overload and hyperferritinaemia are caused by loss-of-function mutations in the SLC11A3 gene that mainly impair macrophage iron recycling. These genetic disorders should be taken into account in the differential diagnosis of unexplained hyperferritinaemia.     

Scanning mutations of the 5'UTR regulatory sequence of L-ferritin by denaturing high-performance liquid chromatography: identification of new mutations

Hereditary hyperferritinaemia cataract syndrome is an autosomal dominant disorder caused by heterogeneous mutations of the iron regulatory element (IRE) in the ferritin l-chain mRNA. The mutations are rare and fast DNA scanning would facilitate diagnosis. The aim of the study was to compare the analytical performances of two fast DNA scanning techniques: denaturing high-performance liquid chromatography (DHPLC) and double-gradient denaturing gradient gel electrophoresis (DG-DGGE). We analysed the sequence encoding the 5' untranslated flanking region of ferritin l-chain mRNA, which includes an IRE stem loop structure. The two systems unambiguously identified all the 12 accessible mutations in a single run, including the difficult C-G transversions. DHPLC and DG-DGGE identified seven abnormal patterns in DNA samples from 47 subjects with unexplained hyperferritinaemia; all had mutations in the IRE sequence, including two not reported before: C36G and A37G. The scanning of 250 DNA samples from subjects genotyped for HFE led to the identification of four new mutations, all outside the IRE structure: C10T, C16T, C90T and del-T156. We conclude that DHPLC, similar to DG-DGGE, detects all the mutations in the l-ferritin 5'UTR sequence in a single run, and that various mutations occur outside the IRE structure.     

Genetic background of primary iron overload syndromes in Japan

The different prevalences of iron overload syndromes between Caucasians and Asians may be accounted for by the differences in genetic background. The major mutation of hemochromatosis in Celtic ancestry, C282Y of HFE, was reported in a Japanese patient. Five patients of 3 families with the hepatic transferrin receptor gene (TFR2)-linked hemochromatosis were found in different areas of Japan, suggesting that TFR2 is a major gene in Japanese people. Three patients with mutations in the hemojuvelin gene, HJV, showed also middle-age-onset hemochromatosis. A heterozygous mutation in the H ferritin gene, FTH1, was found in a family of 3 affected patients. Another autosomal dominant SLC40A1-linked hyperferritinemia (ferroportin disease) was found in 3 patients of 2 families. Two patients with hemochromatosis were free from any mutations in the genes investigated. In conclusion, the genetic backgrounds of Japanese patients with primary iron overload syndromes were partially clarified, showing some phenotype-genotype correlations.