On this page
Congenital cataract (dominant, crystallin)
This condition causes opacity of the eye's lens due to inherited changes in crystallin genes, leading to reduced vision that can range from mild to severe. It affects approximately 1 in 10,000 individuals and typically requires surgical intervention during infancy or childhood to prevent amblyopia and restore visual function.
Overview
Congenital cataract (dominant, crystallin) represents a specific genetic subtype of childhood lens opacity in which clouding of the normally transparent eye lens occurs due to pathogenic variants in genes encoding crystallin proteins. These proteins are the main structural components of the lens, responsible for maintaining its clarity and focusing light onto the retina. When crystallin proteins are disrupted, they can aggregate or misfold, causing the lens to become opaque rather than transparent.
The condition follows an autosomal dominant inheritance pattern, meaning a pathogenic variant in just one copy of an affected gene is sufficient to cause cataracts. Onset is typically at birth or within the first few months of life, though some families show later presentation in early childhood. The severity and specific appearance of lens opacity can vary considerably between families and even between affected members of the same family. Early recognition and timely surgical treatment are essential to prevent permanent visual impairment, as the developing visual system in infants and young children requires clear images to mature properly.
Symptoms & clinical features
The primary clinical feature is clouding of one or both eye lenses, which interferes with the passage of light to the retina. Parents or healthcare providers may notice a white or grey appearance in the pupil (leukocoria) rather than the normal black appearance, particularly visible in photographs where the typical red-eye reflex is absent or appears white. Infants with significant cataract may show reduced visual attention, failure to track objects or faces, or unusual eye movements such as nystagmus (rhythmic oscillation of the eyes).
The specific pattern and location of lens opacity varies depending on which crystallin gene is affected and the nature of the pathogenic variant. Some families show small central opacities that cause minimal visual impairment, whilst others develop dense complete cataracts affecting the entire lens. Additional features may include difficulty seeing in bright light (photophobia), squinting, or delayed visual milestones. In cases where cataracts develop slightly later in infancy or early childhood, children may show deteriorating vision, clumsiness, or difficulty with tasks requiring good visual acuity.
Video: Genetics 101
Affected organs
The eye lens is the primary structure affected in this condition. The lens is a transparent, flexible structure located behind the iris that focuses incoming light onto the retina. It consists largely of crystallin proteins arranged in a precise architecture that maintains transparency. When pathogenic variants disrupt crystallin structure or function, the proteins aggregate abnormally, scattering light rather than allowing it to pass through clearly.
Whilst the lens itself is the site of pathology, the consequences extend to overall visual development. If significant cataract is present during the critical period of visual system maturation (roughly the first 7-8 years of life, with the first few months being most crucial), the lack of clear retinal images can result in amblyopia (lazy eye), where the brain fails to develop normal visual processing even after the cataract is removed. This emphasises the importance of early detection and treatment.
Risks & severity
The severity of visual impairment depends primarily on the density and location of the lens opacity, as well as the age at which treatment occurs. Dense central cataracts present at birth pose the highest risk of permanent visual loss if not surgically addressed within the first few weeks to months of life. Peripheral or less dense opacities may cause milder visual impairment and can sometimes be managed with observation if vision remains adequate for development.
Because crystallin-related cataracts follow an autosomal dominant pattern, approximately 50 per cent of children born to an affected parent will inherit the condition. However, there can be considerable variation in severity even within families, with some individuals having minimal lens changes whilst others require early surgery. Long-term visual outcomes after cataract surgery in infancy are generally favourable, though children typically require lifelong glasses or contact lenses and remain at increased risk of complications such as glaucoma or retinal detachment compared to the general population.
Genetic causes
Congenital cataract (dominant, crystallin) is caused by pathogenic variants in genes encoding crystallin proteins, the major structural proteins of the lens. The three genes most commonly implicated are CRYAA, CRYBB2, and CRYGD. Crystallin proteins are divided into alpha, beta, and gamma families, each with specific roles in maintaining lens transparency and refractive properties. These proteins must remain stable and soluble throughout life, as lens cells lose their nuclei and organelles during development and cannot synthesise new proteins or degrade damaged ones.
CRYAA encodes alpha-crystallin A, a small heat-shock protein that acts as a molecular chaperone, preventing other crystallins from aggregating. Pathogenic variants in CRYAA typically disrupt this chaperone function, allowing abnormal protein aggregation. CRYBB2 encodes a beta-crystallin that contributes to the lens's refractive index gradient, and pathogenic changes can cause protein misfolding or altered interactions with other crystallins. CRYGD encodes gamma-crystallin D, particularly abundant in the lens nucleus, where pathogenic variants commonly lead to protein precipitation and opacity.
Most pathogenic variants are missense changes that alter a single amino acid in the crystallin protein, disrupting its folding, stability, or interactions with other lens proteins. The autosomal dominant inheritance reflects the fact that the abnormal protein produced from one pathogenic allele is sufficient to disrupt the highly ordered lens architecture, even in the presence of normal protein from the other allele.
- CRYAA crystallin alpha A
- CRYBB2 crystallin beta B2
- CRYGD crystallin gamma D
Inheritance pattern
This condition follows an autosomal dominant inheritance pattern. This means that inheriting one pathogenic variant in CRYAA, CRYBB2, CRYGD, or another crystallin gene is sufficient to cause cataracts. Each child of an affected parent has a 50 per cent chance of inheriting the familial pathogenic variant and developing cataracts, regardless of the child's sex.
Because penetrance is typically high (most individuals with a pathogenic variant develop some degree of cataract), family history is usually evident across multiple generations. However, expressivity can be variable, meaning that whilst most carriers develop cataracts, the age of onset, severity, and specific lens appearance can differ even among relatives with the same pathogenic variant. New (de novo) pathogenic variants can also occur, meaning some affected individuals have no family history. Genetic counselling can help families understand recurrence risks and discuss options such as prenatal or preimplantation genetic testing where appropriate.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis typically begins with clinical examination by an ophthalmologist or paediatrician, who may identify lens opacity during routine newborn examination or following parental concern about the child's vision or abnormal pupil appearance. Detailed slit-lamp examination allows characterisation of the cataract's size, density, and location, which can provide clues to the underlying cause.
Genetic testing confirms the diagnosis and identifies the specific causative gene and pathogenic variant. In the NHS, suspected genetic cataract may be referred through clinical genetics services, with testing potentially accessed via the NHS Genomic Medicine Service using relevant PanelApp panels for inherited eye disorders. Genetic confirmation is valuable for several reasons: it establishes recurrence risk for future children, allows predictive testing of at-risk relatives, and may have prognostic implications, as certain gene-phenotype correlations are recognised. Testing typically involves sequencing of known cataract genes, though broader genomic approaches may be warranted if the presentation is atypical or includes features beyond isolated cataract.
Management & lifestyle
Management centres on timely surgical removal of the opaque lens to prevent amblyopia and optimise visual development. The timing of surgery depends on cataract density and whether one or both eyes are affected. Dense bilateral cataracts typically require surgery within the first few weeks of life, whilst unilateral or less severe cases may be addressed somewhat later but still within early infancy. Surgery involves removing the clouded lens material; in older children an artificial intraocular lens may be implanted, though in very young infants this is often deferred, with vision corrected initially using contact lenses or glasses.
Following surgery, children require long-term ophthalmological follow-up to monitor for complications such as glaucoma, posterior capsule opacification, or retinal problems. Optical correction is lifelong, as the eye's natural focusing ability is lost with lens removal. Management of amblyopia through patching or other strategies may be necessary, particularly in unilateral cases. Families benefit from genetic counselling to understand inheritance patterns, recurrence risks, and options for testing other family members. Affected individuals can generally expect good functional vision with appropriate treatment, though they may face restrictions for certain occupations requiring specific visual standards.
UK care pathway
Within the NHS, infants and children with suspected congenital cataract are typically referred urgently to paediatric ophthalmology services for assessment and surgical planning. Genetic testing may be coordinated through clinical genetics services, with access to the NHS Genomic Medicine Service and relevant gene panels for inherited eye conditions. PanelApp includes panels covering inherited cataract alongside other developmental eye disorders, supporting accurate genetic diagnosis.
Families have access to genetic counsellors who can explain inheritance patterns, discuss implications for other family members, and explore reproductive options. Long-term ophthalmic care is provided through specialist paediatric services transitioning to adult ophthalmology, with input from optometry for ongoing optical correction. Multidisciplinary care may also involve orthoptic assessment and support services for children with visual impairment where needed.
Frequently asked questions
Will my child's vision be normal after cataract surgery?
With timely surgery and appropriate optical correction, many children achieve good functional vision. However, vision is rarely completely normal, as the eye lacks its natural lens and children remain at risk of amblyopia if treatment is delayed. Ongoing glasses or contact lenses are always required, and long-term ophthalmology follow-up is essential.
If I have this condition, what is the chance my children will inherit it?
Because this follows autosomal dominant inheritance, each of your children has a 50 per cent chance of inheriting the familial pathogenic variant. However, expressivity can vary, so even affected children may have different severity of cataract compared to you.
Can cataracts in this condition develop later, or are they always present from birth?
Whilst cataracts are typically present at birth or become apparent in early infancy, some families show later onset in childhood. The age of presentation can vary even within the same family, depending on the specific gene and pathogenic variant involved.
Are there other health problems associated with crystallin-related cataracts?
In most cases, crystallin gene variants cause isolated cataracts without affecting other organs. However, a comprehensive clinical assessment is important to exclude syndromic forms of congenital cataract that may involve additional features.