| Knowledge-base field | Evidence-supported summary | Key sources |
|---|---|---|
| Disease / identifiers | Hereditary hyperferritinemia-cataract syndrome (HHCS; OMIM #600886) is a rare Mendelian disorder characterized by persistent hyperferritinemia unrelated to body iron stores and early-onset bilateral cataracts. | [Piperno et al., 2023](https://doi.org/10.3390/ijms24032560); [Moravikova et al., 2020](https://doi.org/10.1016/j.jaapos.2020.07.014) (pqac-00000000, pqac-00000007) |
| Causal gene / inheritance | **FTL** (ferritin light-chain gene); usually heterozygous autosomal-dominant inheritance. De novo disease and rare homozygous affected individuals have been documented. | [Moravikova et al., 2020](https://doi.org/10.1016/j.jaapos.2020.07.014); [Van de Sompele et al., 2017](https://doi.org/10.1007/s00439-017-1835-3) (pqac-00000000, pqac-00000012) |
| Molecular lesion | Pathogenic noncoding substitutions, deletions, and insertion-deletions affect the iron-responsive element (IRE) in the **FTL** 5′ untranslated region, especially its upper stem, conserved hexaloop, and cytosine bulge. A 2019 review catalogued 36 point mutations, nine deletions, and two insertion-deletions associated with HHCS. | [Cadenas et al., 2019](https://doi.org/10.3390/ph12010017); [Millonig et al., 2010](https://doi.org/10.1186/1479-7364-4-4-250) (pqac-00000010, pqac-00000015) |
| Core mechanism | IRE disruption reduces binding of iron-regulatory proteins IRP1/IRP2 and releases normal iron-dependent translational repression, causing constitutive excess L-ferritin synthesis. Functional EMSA evidence showed reduced IRP1 affinity for the c.-151A>G IRE. L-ferritin-rich deposits/crystals in the lens diffract light and produce cataract; absence of systemic iron excess distinguishes HHCS from hemochromatosis. | [Van de Sompele et al., 2017](https://doi.org/10.1007/s00439-017-1835-3); [Piperno et al., 2023](https://doi.org/10.3390/ijms24032560) (pqac-00000007, pqac-00000009, pqac-00000012) |
| Ferritin / iron laboratory pattern | Persistent, often marked serum hyperferritinemia with normal serum iron, transferrin saturation, and body-iron stores. Reported serum ferritin is commonly about 700–2,000 µg/L; one seven-kindred series recorded minima of 740–1,960 µg/L (median 1,420 µg/L). Ferritin may fluctuate but did not increase with age in that series. | [Lachlan et al., 2004](https://doi.org/10.1038/sj.ejhg.5201252); [Cosentino et al., 2016](https://doi.org/10.3109/13816810.2015.1059460) (pqac-00000002, pqac-00000004) |
| Ocular phenotype / onset | Bilateral, generally symmetrical nuclear cataracts can be congenital or recognized in infancy, childhood, or later adulthood. Typical findings include punctate white “breadcrumb-like,” crystalline, sunflower-like, or radial opacities. Cataracts are usually slowly progressive; visual severity and age at surgery vary within and among families. In one British series, median diagnosis was five years and median extraction age was 25 years (range 22–42). | [Lachlan et al., 2004](https://doi.org/10.1038/sj.ejhg.5201252); [Cosentino et al., 2016](https://doi.org/10.3109/13816810.2015.1059460) (pqac-00000001, pqac-00000002, pqac-00000004) |
| Epidemiology | Worldwide distribution; approximate prevalence **1:200,000**, but this is an estimate rather than a population-registry measurement. A 2018 report noted approximately 160 known families/cases. No established sex bias is supported. | [Piperno et al., 2023](https://doi.org/10.3390/ijms24032560); [Ferro et al., 2018](https://doi.org/10.1177/1093526618755200) (pqac-00000005, pqac-00000007) |
| Diagnosis | Suspect HHCS when isolated familial hyperferritinemia coexists with early bilateral cataracts and normal transferrin saturation. Evaluate blood count, serum iron, transferrin/TIBC, transferrin saturation, liver enzymes, and inflammatory causes; slit-lamp examination can reveal characteristic opacities. Confirm by sequencing the **FTL** 5′UTR/IRE and test relatives. Liver biopsy is generally unnecessary when iron overload has been excluded. | [Millonig et al., 2010](https://doi.org/10.1186/1479-7364-4-4-250); [Moravikova et al., 2020](https://doi.org/10.1016/j.jaapos.2020.07.014) (pqac-00000000, pqac-00000006) |
| Management | Hyperferritinemia itself requires no iron-removal treatment. Avoid phlebotomy and iron chelation unless independent iron overload is proven; misdiagnosis has caused iron-deficiency anemia and, in one report, life-threatening hyperammonemia during deferasirox therapy. Monitor vision and perform standard cataract extraction with intraocular-lens management when visual function warrants it. | [Moravikova et al., 2020](https://doi.org/10.1016/j.jaapos.2020.07.014); [Piperno et al., 2023](https://doi.org/10.3390/ijms24032560) (pqac-00000000, pqac-00000003, pqac-00000007) |
| Prognosis | Life-threatening systemic disease or shortened survival has not been demonstrated. Morbidity is predominantly visual and usually amenable to cataract surgery. Serum hyperferritinemia is lifelong but is not, by itself, evidence of organ iron injury. | [Millonig et al., 2010](https://doi.org/10.1186/1479-7364-4-4-250); [Piperno et al., 2023](https://doi.org/10.3390/ijms24032560) (pqac-00000006, pqac-00000007) |
| Evidence gaps | No robust incidence, sex-ratio, penetrance, quality-of-life, survival, or population carrier-frequency studies were identified. Genotype–phenotype prediction remains weak except that rare biallelic variants may be more severe. No HHCS-specific therapeutic trials, validated pharmacotherapy, gene/RNA therapy, direct disease animal model, or single-cell, spatial-transcriptomic, epigenomic, proteomic, metabolomic, or multi-omics study was found in the gathered evidence. | [Cadenas et al., 2019](https://doi.org/10.3390/ph12010017); [Shiels, 2024](https://doi.org/10.3390/genes15060785) (pqac-00000009, pqac-00000015, pqac-00000018, pqac-00000020) |


*Table: Concise evidence table covering the defining clinical, molecular, diagnostic, management, and epidemiologic features of HHCS, together with major evidence gaps. Claims are restricted to the gathered literature and distinguish estimated figures from directly observed findings.*