Hereditary Hyperferritinemia Cataract Research Articles

Differential Degradation of Ferritin H- and L-Chains: Accumulation of L-Chain-Rich Ferritin in Lens Epithelial Cells

The storage of iron by ferritin is determined by tissue-specific composition of its 24 subunits, which are designated as either heavy (H) or light (L). For a better understanding of how lens epithelial cells regulate their ferritin subunit makeup, the degradation pattern of each subunit type was analyzed. In addition, age-related changes in ferritin concentration and subunit makeup were determined. Ferritin turnover in primary cultures of canine lens epithelial cells was determined by metabolic labeling with [(35)S]-methionine. Transient transfection with vectors containing coding sequences for either H- or L-chains were used to modify ferritin subunit makeup. Ferritin concentration was measured by ELISA. Immunodetection and fluorescence immunocytochemistry were used to study age-related changes in ferritin chain concentration. Inhibition of the proteasomal protein degradation pathway by clastolactacystin-beta-lactone had no effect on ferritin degradation, whereas inhibition of lysosomal degradation markedly increased ferritin levels, confirming that this system is involved in ferritin turnover. H-chain ferritin degraded at a faster rate than the L-chain. L-chain-rich ferritin in L-chain-transfected cells formed inclusion bodies that were localized to the cytosol. Similar inclusion bodies were found in older lens cells kept in cell culture for more than 8 days. Steady degradation of H-chain ferritin contributed to the maintenance of a constant level of this chain within the lens epithelial cells. In contrast, slower turnover of the L-chain resulted in accumulation of L-chain-enriched ferritin associated with cytoplasmic inclusion bodies. These L-chain-containing inclusion bodies were found in the cytosol of cells overexpressing L-ferritin chain and in nontransfected cells maintained in culture for 8 to 35 days. Overexpression of the L-chain has been associated with the formation of premature cataracts in humans with hereditary hyperferritinemia cataract syndrome. The formation of inclusion bodies in older lens epithelial cells, as demonstrated in the current investigation, is intriguing and could point to possible involvement of cytoplasmic L-chain-enriched ferritin aggregates in the formation of age-related cataract.

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.

A Point Mutation in the Iron-Responsive Element of the L-Ferritin in a Family with Hereditary Hyperferritinemia Cataract Syndrome

Hereditary hyperferritinemia cataract syndrome is an autosomal dominant condition that is characterized by a high serum ferritin level and bilateral early-onset cataracts in the absence of iron overload. The genetic abnormality is identified as a mutation in the 5' regulatory region of the L-ferritin messenger RNA known as the iron-responsive element (IRE). The IRE controls ferritin synthesis in response to cytoplasmic iron pools by interacting with regulatory proteins called iron responsive proteins. Mutations in the IRE decrease its affinity for iron responsive proteins, leading to the constitutive synthesis of L-ferritin which results in hyperferritinemia and the intracellular accumulation of ferritin in the lens and eventual cataract formation. A 22-year-old woman who was being investigated for hyperferritinemia was diagnosed with hereditary hyperferritinemia cataract syndrome after an extensive workup, including genetic testing for hemochromatosis and a liver biopsy to rule out iron overload. She developed anemia with phlebotomy treatments and subsequently developed symptomatic cataracts. The pedigree of her family affected with cataracts was consistent with an autosomal dominant transmission pattern. DNA was extracted from peripheral leukocytes of eight family members, four of whom were affected by cataracts. Polymerase chain reaction amplification of the 5' region of the L-ferritin gene was performed and a heterozygous point mutation (G32T) was identified in the bulge region of the IRE. The combination of early-onset cataracts and an elevated ferritin level should suggest this genetic syndrome.

Granulocyte function in patients with L-ferritin iron-responsive element (IRE) 39C-->T-positive hereditary hyperferritinaemia-cataract syndrome.

Hereditary hyperferritinaemia-cataract syndrome (HHCS) is an autosomal dominant trait associated with mutations in the iron responsive element (IRE) of the ferritin light-chain (L-ferritin) gene. Patients typically show elevated serum ferritin concentrations without iron overload and a bilateral cataract. Hyperferritinaemia can be associated with granulocyte dysfunction in patients with thalassemia beta and in haemodialysis patients. The effect of increased L-ferritin levels on granulocyte function in patients with HHCS is unknown. We examined glucose uptake, oxidative burst, chemotaxis, phagocytosis, apoptosis and intracellular calcium concentrations in polymorphonuclear leucocytes (PMNLs) of five affected members of a family with HHCS and in five healthy individuals matched for age and gender. Mutation testing revealed a 39C-->T transition in IRE in all five patients with HHCS. Serum ferritin levels of patients ranged between 907 and 2030 microg L(-1), respectively. In comparison with healthy individuals, PMNLs of patients with HHCS showed a significant increase in PMA-mediated stimulation of the oxidative burst, as well as a significantly higher stimulation of glucose uptake but no difference with respect to chemotaxis, phagocytosis, apoptosis and intracellular calcium concentrations. In summary, our study suggests that hyperferritinaemia in patients with IRE 39C-->T-positive HHCS is associated with activation of PMNLs but not with disturbance of fundamental PMNL function.

Clinical features and molecular analysis of seven British kindreds with hereditary hyperferritinaemia cataract syndrome.

Hereditary hyperferritinaemia cataract syndrome (HHCS) is an autosomal dominant disorder characterised by early onset cataracts and increased serum L-ferritin concentration. Affected individuals show nucleotide substitutions in the region of the L-ferritin gene (FTL) that encodes a regulatory sequence within the (mRNA)FTL termed the iron responsive element (IRE). We report the clinical features of seven HHCS kindreds containing 49 individuals with premature cataract. All the probands received diagnoses of HHCS after the incidental discovery of increased serum L-ferritin concentration (median 1420 microg/l; normal range 15-360 microg/l), in most cases during investigation or screening for anaemia. All the probands developed characteristic 'sunflower' morphology cataracts in childhood (median age at diagnosis 5 years), but had no other phenotypic features. All the affected kindreds showed nucleotide substitutions in FTL that were predicted to disrupt function of the (mRNA)FTL IRE. The severity of the clinical phenotype of HHCS was variable both within and between kindreds and showed no clear relationship to FTL genotype. HHCS should be included in the differential diagnosis of hyperferritinaemia and should be carefully distinguished from hereditary haemochromatosis. Measurement of the serum L-ferritin concentration should be included in the investigation of all individuals with early onset cataracts.

Hyperferritinaemia without iron overload: pathogenic and therapeutic implications.

It is not unusual to meet increased levels of ferritinaemia in patients apparently healthy. Among other causes of hyperferritinaemia, recently was described the Hereditary Hyperferritinemia Cataract Syndrome, a genetic condition characterized by increased serum ferritin values without iron overload and bilateral nuclear cataract, both of early onset. It has been demonstrated that single or double point mutations or deletions in the stem-loop structure of the iron regulatory element (I.R.E.) located in the 5 untranslated regions of the ferritin L-subunit gene (19q13.1) are responsible for the upregulation of ferritin. This overexpression only for the L-chain gives rise to typical piles in several tissues. When this altered ferritin accumulates in lens it causes bilateral nuclear cataracts, that is the peculiar sign of this syndrome. It is essential to differentiate true iron overload from Hereditary Hyperferritinaemia Cataract Syndrome (H.H.C.S.), because these patients rapidly develop iron deficient anaemia when venosectioned. Here we describe a case report about a 40 years old healthy female blood donor who presented isolated hyperferritinaemia without iron overload, in the absence of concomitant pathologies. Anamnestic, biochemical, instrumental and clinical investigations led us to diagnose H.H.C.S., a pathology first described in 1995. From 1995 to date about 40 cases concerning patients showing the characteristics of this syndrome from Europe, USA, and Australia were described. Biochemical, genetical and clinical investigations led finally to understand every matter of this pathology, providing conclusive and exhaustive explanations.

Identification of a Mechanism by Which Lens Epithelial Cells Limit Accumulation of Overexpressed Ferritin H-chain

The primary cultures of canine lens epithelial cells were transiently transfected with cDNAs for dog ferritin H- or L-chains in order to study differential expression of these chains. By using chain-specific antibodies, we determined that at 48 h after transfection overexpression of L-chain was much higher (9-fold over control) than that of H-chain (1.7-fold). We discovered that differentially transfected cells secrete overexpressed chains as homopolymeric ferritin into the media. Forty-eight hours after transfection accumulation of H-ferritin in the media was much higher (3-fold) than that of L-ferritin. This resulted in lowering of the concentration of H-chain in the cytosol. Co-transfection of cells with both H- and L-chain cDNAs increased the intracellular levels of H-chain and eliminated secretion of H-ferritin to the media. We concluded that lens epithelial cells differentially regulate concentration of both ferritin chains in the cytosol. The overexpressed L-chain accumulated in the cytosol as predominantly homopolymeric L-ferritin. This is in contrast to H-chain, which is removed to the media unless there is an L-chain available to form heteropolymeric ferritin. These data indicate that the inability of cells to more strictly control cytosolic levels of L-chain may augment its accumulation in lenses of humans with hereditary hyperferritinemia cataract syndrome, which is caused by overexpression of L-chain due to mutation in the regulatory element in the untranslated region of the mRNA of the chain.

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.

Denaturing gradient gel electrophoresis screening for mutations in the hereditary hyperferritinaemia cataract syndrome.

Hereditary hyperferritinaemia cataract syndrome (HHCS) is characterized by hyperferritinaemia without iron overload. It is essential to differentiate true iron accumulation from HHCS as these patients rapidly develop iron-deficient anaemia when subjected to phlebotomies. The diagnosis of HHCS relies on the identification of point mutations or deletions present in the iron-responsive element of the first exon of the L-ferritin gene. However, many samples referred for diagnosis of putative HHCS are normal. To avoid unnecessary DNA sequencing, we have developed a diagnosis strategy based on the screening of the target DNA region by denaturing gradient gel electrophoresis. This method enabled the accurate identification of 11 different previously known mutations. This strategy will be of interest for family studies or for the screening of large series of patients.

The lens in hereditary hyperferritinaemia cataract syndrome contains crystalline deposits of L-ferritin

BACKGROUND/AIMHereditary hyperferritinaemia cataract syndrome (HHCS) is an autosomal dominant disorder characterised by elevated serum L-ferritin and bilateral cataracts. The ocular manifestations of this disorder are poorly studied. This study therefore...

High Level of Ferritin Light Chain mRNA in Lens

Ferritin is of particular interest with regard to cataract because (i) cataract occurs in individuals with hereditary hyperferritinemia cataract syndrome (HHCS), a condition in which ferritin light chain (L-ferritin) protein is overexpressed systemically, and (ii) ferritin is an important regulator of oxidative stress, a primary factor in the etiology of aging-related cataract. From gene array analysis two novel observations were made with respect to ferritin gene expression: first, lenses from guinea pigs and humans have disproportionately high levels of L-ferritin mRNA relative to the amounts of ferritin protein present, and second, L-ferritin message increased markedly in lenses from guinea pigs with hereditary nuclear cataract. The human lens L-ferritin sequence was identical to previous data from human liver; the guinea pig sequence was 86% identical to the human sequence at the amino acid level. Despite mRNA levels similar to those of major lens crystallins, lens ferritin was undetectable by Western blot techniques.

Clinical Severity and Thermodynamic Effects of Iron-responsive Element Mutations in Hereditary Hyperferritinemia-Cataract Syndrome

Hereditary hyperferritinemia-cataract syndrome (HHCS) is a novel genetic disorder characterized by elevated serum ferritin and early onset cataract formation. The excessive ferritin production in HHCS patients arises from aberrant regulation of L-ferritin translation caused by mutations within the iron-responsive element (IRE) of the L-ferritin transcript. IREs serve as binding sites for iron regulatory proteins (IRPs), iron-sensing proteins that regulate ferritin translation. Previous observations suggested that each unique HHCS mutation conferred a characteristic degree of hyperferritinemia and cataract severity in affected individuals. Here we have measured the in vitro affinity of the IRPs for the mutant IREs and correlated decreases in binding affinity with clinical severity. Thermodynamic analysis of these IREs has also revealed that although some HHCS mutations lead to changes in the stability and secondary structure of the IRE, others appear to disrupt IRP-IRE recognition with minimal effect on IRE stability. HHCS is a noteworthy example of a human genetic disorder that arises from mutations within a protein-binding site of an mRNA cis-acting element. Analysis of the effects of these mutations on the energetics of the RNA-protein interaction explains the phenotypic variabilities of the disease state.

Coinheritance of Alleles Associated With Hemochromatosis and Hereditary Hyperferritinemia-Cataract Syndrome

To the Editor: A 52-year-old white woman was referred for additional evaluation because she was intolerant of phlebotomy therapy of her presumed hemochromatosis and iron overload, and her serum ferritin concentration had not changed significantly. Her diagnosis was based on serum iron 122 μg/dL,

Analysis of Ferritins in Lymphoblastoid Cell Lines and in the Lens of Subjects With Hereditary Hyperferritinemia-Cataract Syndrome

AbstractHereditary hyperferritinemia-cataract syndrome (HHCS) is an autosomal and dominant disease caused by heterogeneous mutations in the iron responsive element (IRE) of the 5′ untranslated flanking region of ferritin L-chain mRNA, which reduce the binding to the trans iron regulatory proteins and make L-chain synthesis constitutively upregulated. In the several families identified so far, the serum and tissue L-ferritin levels are fivefold to 20-fold higher than in nonaffected control subjects, iron metabolism is apparently normal, and the only relevant clinical symptom is early onset, bilateral cataract. Some pathogenetic aspects of HHCS remain obscure, with particular reference to the isoferritins produced by HHCS cells, as well as the mechanism of cataract formation. We analyzed lymphoblastoid cell lines obtained from two nonaffected control subjects and from HHCS patients carrying the substitution A40G (Paris-1), G41C (Verona-1), and the deletion of the residues 10-38 (Verona-2) in the IRE structure. Enzyme-linked immunosorbent assays specific for the H- and L-type ferritins showed that L-ferritin levels were up to 20-fold higher in HHCS than in control cells and were not affected by iron supplementation or chelation. Sequential immunoprecipitation experiments of metabolically-labeled cells with specific antibodies indicated that in HHCS cells about half of the L-chain was assembled in L-chain homopolymers, which did not incorporate iron, and the other half was assembled in isoferritins with a high proportion of L-chain. In control cells, all ferritin was assembled in functional heteropolymers with equivalent proportion of H- and L-chains. Cellular and ferritin iron uptake was slightly higher in HHCS than control cells. In addition, we analyzed the lens recovered from cataract surgery of a HHCS patient. We found it to contain about 10-fold more L-ferritin than control lens. The ferritin was fully soluble with a low iron content. It was purified and partially characterized. Our data indicate that: (1) in HHCS cells a large proportion of L-ferritin accumulates as nonfunctional L-chain 24 homopolymers; (2) the concomitant fivefold to 10-fold expansion of ferritin heteropolymers, with a shift to L-chain–rich isoferritins, does not have major effects on cellular iron metabolism; (3) L-chain accumulation occurs also in the lens, where it may induce cataract formation by altering the delicate equilibrium between other water-soluble proteins (ie, crystallins) and/or the antioxidant properties.

Analysis of Ferritins in Lymphoblastoid Cell Lines and in the Lens of Subjects With Hereditary Hyperferritinemia-Cataract Syndrome

Hereditary hyperferritinemia-cataract syndrome (HHCS) is an autosomal and dominant disease caused by heterogeneous mutations in the iron responsive element (IRE) of the 5′ untranslated flanking region of ferritin L-chain mRNA, which reduce the binding to the trans iron regulatory proteins and make L-chain synthesis constitutively upregulated. In the several families identified so far, the serum and tissue L-ferritin levels are fivefold to 20-fold higher than in nonaffected control subjects, iron metabolism is apparently normal, and the only relevant clinical symptom is early onset, bilateral cataract. Some pathogenetic aspects of HHCS remain obscure, with particular reference to the isoferritins produced by HHCS cells, as well as the mechanism of cataract formation. We analyzed lymphoblastoid cell lines obtained from two nonaffected control subjects and from HHCS patients carrying the substitution A40G (Paris-1), G41C (Verona-1), and the deletion of the residues 10-38 (Verona-2) in the IRE structure. Enzyme-linked immunosorbent assays specific for the H- and L-type ferritins showed that L-ferritin levels were up to 20-fold higher in HHCS than in control cells and were not affected by iron supplementation or chelation. Sequential immunoprecipitation experiments of metabolically-labeled cells with specific antibodies indicated that in HHCS cells about half of the L-chain was assembled in L-chain homopolymers, which did not incorporate iron, and the other half was assembled in isoferritins with a high proportion of L-chain. In control cells, all ferritin was assembled in functional heteropolymers with equivalent proportion of H- and L-chains. Cellular and ferritin iron uptake was slightly higher in HHCS than control cells. In addition, we analyzed the lens recovered from cataract surgery of a HHCS patient. We found it to contain about 10-fold more L-ferritin than control lens. The ferritin was fully soluble with a low iron content. It was purified and partially characterized. Our data indicate that: (1) in HHCS cells a large proportion of L-ferritin accumulates as nonfunctional L-chain 24 homopolymers; (2) the concomitant fivefold to 10-fold expansion of ferritin heteropolymers, with a shift to L-chain–rich isoferritins, does not have major effects on cellular iron metabolism; (3) L-chain accumulation occurs also in the lens, where it may induce cataract formation by altering the delicate equilibrium between other water-soluble proteins (ie, crystallins) and/or the antioxidant properties.

Hereditary Hyperferritinemia-Cataract Syndrome: Two Novel Mutations in the L-Ferritin Iron-Responsive Element

To the Editor: Cazzola et al[1][1] recently reported two kindreds with hereditary hyperferritinemia cataract syndrome (HHCS) associated with novel point mutations within a regulatory stem-loop motif in the L-ferritin mRNA termed the iron-responsive element (IRE). Affected individuals showed a

A Point Mutation in the Bulge of the Iron-Responsive Element of the L Ferritin Gene in Two Families With the Hereditary Hyperferritinemia-Cataract Syndrome

The molecular basis for the recently described hereditary hyperferritinemia-cataract syndrome is the presence of a mutation in the iron-responsive element (IRE) of the L ferritin gene, located on chromosome 19q13.3-13.4. Two mutations have been reported so far, altering adjacent nucleotides in the IRE loop, in a region that has been extensively studied in vitro and shown to mediate high affinity interaction with the iron-responsive protein. In this report, we describe two families with a new mutation in the bulge of the IRE stem, and we show that this mutation alters the protein-binding affinity of the IRE in vitro to the same extent as the loop mutation. In addition, we present evidence that some variability in the age of onset of cataract can be associated with this genetic syndrome, probably because of additional genetic or environmental factors that modulate the penetrance of the L ferritin defect in the lens. We confirm that the patients do not have increased iron stores despite the persistence of elevated serum ferritin levels and that, accordingly, they do not tolerate well venesection therapy. Further studies will be necessary to elucidate the mechanism responsible for the onset of cataract.

A Point Mutation in the Bulge of the Iron-Responsive Element of the L Ferritin Gene in Two Families With the Hereditary Hyperferritinemia-Cataract Syndrome

AbstractThe molecular basis for the recently described hereditary hyperferritinemia-cataract syndrome is the presence of a mutation in the iron-responsive element (IRE) of the L ferritin gene, located on chromosome 19q13.3-13.4. Two mutations have been reported so far, altering adjacent nucleotides in the IRE loop, in a region that has been extensively studied in vitro and shown to mediate high affinity interaction with the iron-responsive protein. In this report, we describe two families with a new mutation in the bulge of the IRE stem, and we show that this mutation alters the protein-binding affinity of the IRE in vitro to the same extent as the loop mutation. In addition, we present evidence that some variability in the age of onset of cataract can be associated with this genetic syndrome, probably because of additional genetic or environmental factors that modulate the penetrance of the L ferritin defect in the lens. We confirm that the patients do not have increased iron stores despite the persistence of elevated serum ferritin levels and that, accordingly, they do not tolerate well venesection therapy. Further studies will be necessary to elucidate the mechanism responsible for the onset of cataract.

Hereditary Hyperferritinemia-Cataract Syndrome Caused by a 29-Base Pair Deletion in the Iron Responsive Element of Ferritin L-Subunit Gene

AbstractIron availability regulates ferritin synthesis posttranscriptionally by the interaction between iron-regulatory proteins (IRPs) and an iron responsive element (IRE), a stem-loop sequence located on the 5′ untranslated region of ferritin mRNA. IRPs recognize IREs as a sequence/structure motif, blocking ferritin translation. Recently, we and others independently described families with a combination of hyperferritinemia (serum L-ferritin ≥ 1,000 μg/L, without iron overload) and congenital bilateral cataract, transmitted as an autosomal-dominant trait. The molecular basis were two distinct point mutations in the highly conserved CAGUG(X) hexaloop of L-ferritin IRE on chromosome 19. A new three-generation family with a similar phenotype and a unique genotype is here reported. DNA amplification by polymerase chain reaction and sequence analysis showed a 29-base pair deletion in the L-ferritin IRE, involving the whole 5′ sequence essential to the base pairing of the IRE stem. This deletion is predicted to cause the disruption of IRE stem-loop secondary structure and the nearly complete abolition of the negative control of ferritin synthesis by IRE/IRP binding. Hereditary Hyperferritinemia-Cataract Syndrome (HHCS) appears as a new genetic disorder with a unique phenotype associated with at least four different mutations in the L-ferritin IRE. Hematologists should take into account HHCS in the differential diagnosis of unexplained hyperferritinemia.

Hereditary Hyperferritinemia-Cataract Syndrome: Relationship Between Phenotypes and Specific Mutations in the Iron-Responsive Element of Ferritin Light-Chain mRNA

AbstractRecent reports have described 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. We have studied the molecular pathogenesis of hyperferritinemia in two families showing different phenotypic expression of this new genetic disorder. Serum ferritin levels ranged from 950 to 1,890 μg/L in affected individuals from family 1, and from 366 to 635 μg/L in those from family 2. Cataract was clinically manifested in family 1 and asymptomatic in family 2. By using monoclonal antibodies specific for the H and L ferritin subunits, serum ferritin was found to be essentially L type in both normal and affected individuals. The latter also showed normal amounts of H-type ferritin in circulating mononuclear cells; on the contrary, L-type ferritin contents were 13 times normal in family 1 and five times normal in family 2 on average. Serum ferritin was glycosylated in both normal and affected individuals. There was a close relationship between mononuclear cell L-type ferritin content and serum ferritin concentration (r = 0.95, P < .00001), suggesting that the excess production of ferritin in cells was directly responsible for the hyperferritinemia. The dysregulated L-subunit synthesis was found to result from different point mutations in a noncoding sequence of genomic L-subunit DNA, which behaves as an mRNA cis-acting element known as iron regulatory element (IRE). Affected individuals from family 1 were heterozygous for a point mutation (a single G to A change) in the highly conserved, three-nucleotide motif forming the IRE bulge. Affected members from family 2 were heterozygous for a double point mutation in the IRE lower stem. Using a gel retardation assay, the observed molecular lesions were shown to variably reduce the IRE affinity for an iron regulatory protein (IRP), which inhibits ferritin mRNA translation. The direct relationship between the degree of hyperferritinemia and severity of cataract suggests that this latter is the consequence of excessive ferritin production within the lens fibers. These findings provide strong evidence that serum ferritin is a byproduct of intracellular ferritin synthesis and that the L-subunit gene on chromosome 19 is the source of glycosylated serum ferritin. From a practical standpoint, this new genetic disorder should be taken into account by clinicians when facing a high serum ferritin in an apparently healthy person.