Peters anomaly

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Peters anomaly is characterized by eye problems that occur in an area at the front part of the eye known as the anterior segment. The anterior segment consists of structures including the lens, the colored part (iris) of the eye, and the clear covering of the eye (cornea). During development of the eye, the elements of the anterior segment form separate structures. However, in Peters anomaly, development of the anterior segment is abnormal, leading to incomplete separation of the cornea from the iris or the lens. As a result, the cornea is cloudy (opaque), which causes blurred vision. The opaque area (opacity) of the cornea varies in size and intensity from a small, faint streak to a large, white cloudy area that covers the front surface of the eye. Additionally, the location of the opacity varies; the cloudiness may be at the center of the cornea or off-center. Large, centrally located opacities tend to cause poorer vision than smaller, off-center ones.

Nearly half of the individuals affected with Peters anomaly have low vision early in life and about a quarter are legally blind. Due to a lack of visual stimulation, some individuals develop "lazy eye" (amblyopia). Peters anomaly is often associated with other eye problems, such as increased pressure within the eye (glaucoma), clouding of the lens (cataract), and unusually small eyeballs (microphthalmia). In most cases, Peters anomaly is bilateral, which means that it affects both eyes, although the level of vision impairment may be different in each eye. These individuals may have eyes that do not point in the same direction (strabismus). In some people with Peters anomaly, corneal clouding improves over time leading to improved vision.

There are two types of Peters anomaly, which are distinguished by their signs and symptoms. Peters anomaly type I is characterized by an incomplete separation of the cornea and iris and mild to moderate corneal opacity. Type II is characterized by an incomplete separation of the cornea and lens and severe corneal opacity that may involve the entire cornea.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the FOXC1, PAX6, PITX2, or CYP1B1 gene can cause Peters anomaly. The FOXC1, PAX6, and PITX2 genes are all members of a family called homeobox genes that direct the formation of many parts of the body. These three genes are involved in the development of the anterior segment of the eye. The CYP1B1 gene provides instructions for making an enzyme that is active in many tissues, including the eye. The enzyme's role in these tissues is unclear; it is likely involved in the development of the anterior segment.

Mutations in any of these four genes disrupt development of the anterior segment of the eye. These mutations can lead to severe developmental problems, such as incomplete separation of eye structures and complete corneal opacity, or they can result in minor eye abnormalities including small, faint opacities. It is likely that mutations that cause a complete absence of protein function result in the most severe eye problems. It is unknown why both eyes are affected in some cases and in others only one eye is abnormal.

In many cases of Peters anomaly, there is no mutation identified in any of these four genes. The cause of the condition in these cases is unknown.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Most cases of Peters anomaly are sporadic, which means that they occur in people with no apparent history of the disorder in their family. In many of these sporadic cases the genetic cause of the condition is unknown. However, some of these cases are caused by a new mutation in one of the previously mentioned genes or by the inheritance of a mutation from unaffected parents. In rare cases, the condition (or related eye disorders) has been reported to occur in multiple members of the same family.

Whether sporadic or inherited, when Peters anomaly is caused by mutations in the CYP1B1 gene, it follows an autosomal recessive pattern of inheritance. Autosomal recessive inheritance means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. When caused by mutations in the FOXC1, PAX6, or PITX2 gene, the condition follows an autosomal dominant pattern of inheritance, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

The exact prevalence of Peters anomaly is unknown. This condition is one of a group of disorders known as congenital corneal opacities, which affect 3 to 6 individuals per 100,000.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Anterior synechiae of the anterior chamber · Very frequent (99-80%)

Adhesions between the iris and the cornea.

Central opacification of the cornea · Very frequent (99-80%)

Reduced transparency of the central portion of the corneal stroma.

Opacification of the corneal stroma · Very frequent (99-80%)

Reduced transparency of the stroma of cornea.

Peters anomaly · Obligate (100%)

A form of anterior segment dysgenesis in which abnormal cleavage of the anterior chamber occurs. Peters anomaly is characterized by central, paracentral, or complete corneal opacity.

Subcapsular cataract · Very frequent (99-80%)

A cataract that affects the region of the lens directly beneath the capsule of the lens.

Thinning of Descemet membrane · Very frequent (99-80%)

A reduction in the thickness of Descemet's membrane.

Developmental glaucoma · Frequent (79-30%)

Glaucoma which forms during the early years of a child's life is called developmental or congenital glaucoma.

Nystagmus · Very rare (<4-1%)

Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.

Other findings in the same source

From: Orphanet

Additional reported features include Strabismus (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Peters anomaly is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Peters anomaly. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.