Brittle Cornea Syndrome

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Article initiated by:
Kieley Trempy, Kaitlyn Hunter, Eric J. Niespodzany, MD
All contributors:
Kieley Trempy, Kaitlyn Hunter, Vatinee Y. Bunya, MD, MSCE, Colleen Halfpenny, M.D., Eric J. Niespodzany, MD, Neha Shaik, MD, Megan Kasetty, MD
Assigned editor:
Megan Kasetty, MD
Review:
Assigned status Up to Date
 by Megan Kasetty, MD on August 28, 2025.


Brittle Cornea Syndrome
DiseasesDB
4131
ICD-10
[1]79.6
OMIM
229200
MedlinePlus
001468
MeSH
C536192


Disease Entity

Disease

Brittle Cornea Syndrome (BCS) is a rare autosomal recessive connective tissue disease characterized by progressive corneal thinning, ectasia and blue sclera, resulting in increased susceptibility for perforation and rupture. First described by Israeli ophthalmologist, Dr. Richard Stein in 1968, who stated that the cornea broke into “crumbs” during suturing in an attempt to repair a brittle cornea following perforation.[1]

Genetics

BCS is genetically heterogeneous.[2] There are 2 types of BCS:

1. Brittle Cornea Syndrome Type 1: Type 1 results from a homozygous mutation in the zinc finger protein-469 gene (ZNF469/KIAA1858) on chromosome 16q24. Genome-wide association studies have associated this locus with changes in central corneal thickness[3][4] through pathways regulating extracellular matrix. Mutations in ZNF469 have also been associated with keratoconus.[5] In these instances, keratoconus corresponds with heterozygous missense mutations of ZNF469 while BCS corresponds with homozygous frameshift or truncating mutations of ZNF469.[6][7] Some dispute that ZNF469 mutations are associated with keratoconus due to lack of replicability after larger cohort analyses.[8][9][10]
2. Brittle Cornea Syndrome Type 2: Type 2 results from a homozygous mutation in the PR domain-containing protein-5 gene (PRDM5/PFM2) on chromosome 4q27. PRDM5 is also implicated in corneal thickness,[2] as well as in development of the retina.[11]

Epidemiology

The prevalence of BCS is less than 1 per million.[11] The syndrome has autosomal recessive inheritance pattern.[6]

Pathophysiology

Both ZNF469 and PRDM5 gene products are involved in transcriptional regulation of the extracellular matrix.[6][12][13]

ZNF469 is a single exon gene whose protein product is made up of three, type C2H2, zinc-finger domains near the 3′ end and is involved in sequence-specific DNA-binding motifs and protein-protein interactions.[6][13] An in vivo study showed decrease in extracellular matrix genes (CLU, GPC6, PCOLCE2, THBS1) in ZNF469 mutant fibroblasts.[13]

The protein produced by PRDM5 is involved in the regulation of hematopoiesis-associated protein-coding and microRNA genes that are associated with cell fate and Wnt signaling.[2] PRDM5 has also been implicated in regulation of fibrillar collagens (COL4A1, COL11A1), connective tissue (HAPLN1), and cell migration/adhesion (EDIL3, TGFB2).[2][13]

An in vivo study of fibroblasts from cultured BCS patients demonstrated that genes (COL4A1, COL11A1, EDIL3, HAPLN1, TGFβ2) involved in the development and maintenance of the extracellular matrix were reduced.[2] Additionally, immunofluorescence of the fibroblasts showed disruption in the organization of collagens type I/III, fibronectin, and α2β1/α5β1 integrins, all a part of the extracellular matrix[2].

Diagnosis

History

Patients may present in childhood with corneal perforation or rupture, and mean age of rupture occurs around 4.3 years (range 1.5-19 years) according to reported literature.[14] Family history is often remarkable for consanguinity.[15]

Signs & Symptoms

Limbus to limbus corneal thinning and ectasia as well as blueish discoloration of the sclera will be present.[15] BCS patients often have central corneal thickness less than 400 μm.[11][15] Scarring of the cornea may be found in areas where Descemet membrane rupture has occurred. Other ocular signs include high myopia and retinal detachment.[15]

Systemic manifestations include joint hypermobility, skin hyperelasticity, hypercompliant tympanic membranes, osteopenia, hip dysplasia, arachnodactyly, contractures especially of the fifth digit, hypotonia in infancy, abnormal dentition, hernias, scoliosis or kyphoscoliosis.[11] Patients may also have hearing loss, which can be conductive or sensorineural, however this mechanism is unclear since both types have been found in BCS patients.[15] BCS has also been associated with red hair.[1][6][16]

Carriers of BCS have been reported to develop myopia and a mild degree of corneal thinning.[2]

Differential Diagnosis

  • Kyphoscoliotic Ehlers Danlos Syndrome: BCS has many intersections with other types of EDS, especially the kyphoscoliotic type. BCS was previously considered kyphoscoliotic type.[11] Kyphoscoliotic type and BCS patients share similar signs of kyphoscoliosis, dental abnormalities, arachnodactyly, hypermobility, osteopenia, and hypotonia in infancy. Kyphoscoliotic type patients differ in their tendency for arterial rupture and early death due to cardio-pulmonary insufficiency.[14][17] Kyphoscoliotic type is due to a deficiency in lysyl hydroxylase-1, which is involved in post-translational modification of collagen.[11] This type can be diagnosed by increased urinary output of total pyridinoline content and lysyl pyridinoline (to hydroxylysyl pyridinoline); however, this is normal in BCS patients.[13][14]
  • Marfan syndrome: Marfan syndrome and BCS patients share similar signs of blue sclerae and ocular fragility. Marfan syndrome patients differ in their tendency for aortic dissection, tall stature, and ectopia lentis.[15]
  • Osteogenesis imperfecta: Osteogenesis imperfecta shares similar characteristics with BCS including blue sclerae, thin corneas, conductive hearing loss, abnormal dentition, and skin hyperelasticity, but differs in the tendency for recurrent fractures.[18][15]

Diagnostic Procedures

Diagnosis is made based on the constellation of clinical manifestations described. Corneal thinning/ectasia can be evaluated with pachymetry and topography/tomography. If there is personal or family history of ocular rupture or BCS, genetic testing is recommended.[15] Genetic testing for carriers may inform risk of ectasia and aid genetic counseling.[2] BCS genetic panels available in the United States are listed here.

Management

General Treatment

The main treatment for Brittle Cornea Syndrome (BCS) patients is early diagnosis and taking measures to prevent corneal perforation. Protective eyewear (such as polycarbonate glasses) and disease education for parents and school staff is essential to decrease risk of rupture.

Surgical management of corneal perforation or planned penetrating keratoplasty is challenging given the exceedingly thin, floppy tissue and high risk of wound leakage. During a penetrating keratoplasty performed on a BCS patient with corneal scarring by Dr. Luis Izquierdo and colleagues, an intraoperative corneal rupture occurred after attempt to rotate a 10-0 nylon knot.[18] The surgeons subsequently patched this area with a scleral patch graft, though this was described as difficult due to the tissue thickness difference between the donor and recipient as well as the delicacy of the recipient tissue. Ultimately, the graft was successful and vision improved. They recommend longer suture bites into the recipient cornea for better security between the two tissues and to reduce risk of cheese-wiring. They also recommend patching scleral or corneal allografts onto weak areas. Though they did not use 11-0 nylon, they mentioned that this size could be better than 10-0 for these cases.[11][18] Dr. Ken Nischal, Director of Pediatric Ophthalmology at the University of Pittsburgh, has discussed using an overlay epikeratoplasty graft for additional ocular protection.[19] Dr. Nischal recommends performing a paracentesis prior in order to lower the intraocular pressure, to allow the tissues to appose one another during suturing. Additionally, he recommends making a smaller incision than intended due to the incisions' tendency to expand. Finally, he advises prophylactic use of IOP lowering medications for BCS patients to prevent glaucoma and also to reduce risk for spontaneous rupture.[19]

Corneal collagen cross-linking has been attempting to slow or halt corneal thinning associated with BCS, though the procedure is controversial for this disease given the underlying pathophysiology and risk of perforation.[19][20]

When the rupture is beyond repair, enucleation may be considered.

Prognosis

Visual prognosis is generally poor for patients with BCS who may have decreased vision related to progressive ectasia and are at high risk of rupture from even minor ocular trauma. Due to difficulty of surgical repair, blindness following perforation or rupture is common, occurring in more than half of published cases.[14][20] Perforation or rupture can also occur spontaneously.[14][18]

Systemically, BCS has better prognosis than its close relative, kyphoscoliotic type, as life expectancy appears to be normal and the extraocular manifestations of BCS are non-life threatening.[13][14]

Additional Resources

References

  1. ↑ 1.0 1.1 Stein R, Lazar M, Adam A. Brittle Cornea. Am J Ophthalmol. 1968;66(1):67-69. doi:10.1016/0002-9394(68)91789-3.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Burkitt Wright EMM, Spencer HL, Daly SB, et al. Mutations in PRDM5 in brittle cornea syndrome identify a pathway regulating extracellular matrix development and maintenance. Am J Hum Genet. 2011;88(6):767-777. doi:10.1016/j.ajhg.2011.05.007
  3. ↑ Lu Y, Dimasi DP, Hysi PG, et al. Common genetic variants near the brittle cornea syndrome locus ZNF469 influence the blinding disease risk factor central corneal thickness. PLoS Genetics. 2010;6(5):e1000947. doi:10.1371/journal.pgen.1000947
  4. ↑ Lu Y, Vitart V, Burdon KP, et al. Genome-wide association analyses identify multiple loci associated with central corneal thickness and keratoconus. Nat Genet. 2013;45(2):155-163. doi:10.1038/ng.2506
  5. ↑ Vincent AL, Jordan CA, Cadzow MJ, Merriman TR, McGhee CN. Mutations in the zinc finger protein gene, ZNF469, contribute to the pathogenesis of keratoconus. Invest Ophthalmol Vis Sci. 2014;55(9):5629. doi:10.1167/iovs.14-14532
  6. ↑ 6.0 6.1 6.2 6.3 6.4 Abu A, Frydman M, Marek D, et al. Deleterious mutations in the zinc-finger 469 gene cause brittle cornea syndrome. Am J Hum Genet. 2008;82(5):1217-1222. doi:10.1016/j.ajhg.2008.04.001
  7. ↑ Yildiz E, Bardak H, Gunay M, et al. Novel zinc finger protein gene 469 (ZNF469) variants in advanced keratoconus. Curr Eye Res. 2017;42(10):1396-1400. doi:10.1080/02713683.2017.1325910
  8. ↑ Davidson AE, Borasio E, Liskova P, et al. Brittle cornea syndrome ZNF469 mutation carrier phenotype and segregation analysis of rare ZNF469 variants in Familial Keratoconus. Investig Ophthalmol Vis Sci. 2015;56(1):578-586. doi:10.1167/iovs.14-15792
  9. ↑ Karolak JA, Gambin T, Rydzanicz M, et al. Evidence against ZNF469 being causative for keratoconus in Polish patients. Acta Ophthalmol. 2016;94(3):289-294. doi:10.1111/aos.12968
  10. ↑ Lucas SE, Zhou T, Blackburn NB, et al. Rare, potentially pathogenic variants in ZNF469 are not enriched in keratoconus in a large Australian cohort of European descent. Investig Ophthalmol Vis Sci. 2017;58(14):6248. doi:10.1167/iovs.17-22417
  11. ↑ 11.0 11.1 11.2 11.3 11.4 11.5 11.6 Walkden A, Burkitt-Wright E, Au L. Brittle cornea syndrome: current perspectives. Clinical Ophthalmol. 2019;13:1511-1516. doi:10.2147/opth.s185287
  12. ↑ Galli GG, Honnens de Lichtenberg K, Carrara M, et al. PRDM5 regulates collagen gene transcription by association with RNA polymerase II in developing bone. PLoS Genet. 2012;8(5). doi:10.1371/journal.pgen.1002711
  13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 Rohrbach M, Spencer HL, Porter LF, et al. Znf469 frequently mutated in the brittle cornea syndrome (BCS) is a single exon gene possibly regulating the expression of several extracellular matrix components. Mol Genet Metab. 2013;109(3):289-295. doi:10.1016/j.ymgme.2013.04.014
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 Al-Hussain H, Zeisberger SM, Huber PR, Giunta C, Steinmann B. Brittle cornea syndrome and its delineation from the kyphoscoliotic type of Ehlers-Danlos Syndrome (EDS VI): Report on 23 patients and review of the literature. Am J Med Genet. 2003;124A(1):28-34. doi:10.1002/ajmg.a.20326
  15. ↑ 15.0 15.1 15.2 15.3 15.4 15.5 15.6 15.7 Burkitt Wright EMM, Porter LF, Spencer HL, et al. Brittle cornea syndrome: Recognition, molecular diagnosis and management. Orphanet J Rare Dis. 2013;8(1). doi:10.1186/1750-1172-8-68
  16. ↑ Ticho U, Ivry M, Merin S. Brittle cornea, blue sclera, and red hair syndrome (the brittle cornea syndrome). Br J Ophthalmol. 1980;64(3):175-177. doi:10.1136/bjo.64.3.175
  17. ↑ Al-Owain M, Al-Dosari MS, Sunker A, Shuaib T, Alkuraya FS. Identification of a novel ZNF469 mutation in a large family with Ehlers–Danlos Phenotype. Gene. 2012;511(2):447-450. doi:10.1016/j.gene.2012.09.022
  18. ↑ 18.0 18.1 18.2 18.3 Izquierdo L, Mannis MJ, Marsh PB, Yang SP, McCarthy JM. Bilateral spontaneous corneal rupture in brittle cornea syndrome. Cornea. 1999;18(5):621. doi:10.1097/00003226-199909000-00019
  19. ↑ 19.0 19.1 19.2 Stuart A. Genetic Disorders of the Cornea: Preventing Surgical Surprises. EyeNet Mag. 2020;24(5):45-46. https://www.aao.org/eyenet/article/genetic-disorders-of-the-cornea
  20. ↑ 20.0 20.1 Kaufmann C, Schubiger G, Thiel MA. Corneal cross-linking for brittle cornea syndrome. Cornea. 2015;34(10):1326-1328. doi:10.1097/ico.0000000000000577
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