Is Heterochromia Genetic? Types, Symptoms, and Complications

Key Takeaways

• Not always genetic; genes like OCA2 and HERC2 can influence eye color variation - Jump to Section
• There are three types: central, complete, and sectoral heterochromia - Jump to Section
• Causes include genetics, melanin distribution, eye injuries, and certain conditions - Jump to Section
• Heterochromia usually doesn't affect vision or indicate health issues - Jump to Section
• Heterochromia can appear at any age and is rare; not necessarily inherited or a birth defect - Jump to Section

Heterochromia is a medical phenomenon where an individual can have different colored eyes or several different colors in the same eye.

Usually, it can happen when a unique mix of colors is present in the iris, the colored part of your eyes.

Someone with heterochromia can have one light blue iris while the other is brown or even a dash of blue within brown eyes.

Many factors can cause it, including:

• Genetics
• Eye injuries
• Specific medical conditions
• Other developmental factors

Is Heterochromia Genetic?

Heterochromia can have a genetic component—but not in every case.

The type and amount of pigments in the irises dictate the color of a person’s eyes. The genes that you inherit from your parents play a role in deciding how much of these pigments are produced.

With heterochromia, genetic discrepancies can lead to differences in how much pigment is made in each eye or even within the same eye (partial heterochromia). The result can be two different eye colors in one person.

Research shows that genes such as oculocutaneous albinism II (OCA2) and HECT And RLD Domain Containing E3 Ubiquitin Protein Ligase 2 (HERC2) can affect eye color, which can contribute to heterochromia.¹

OCA2 produces a protein that assists in developing pigments, while HERC2 regulates OCA2 activities. Mutations in either gene can lead to one eye having less pigment than the other, resulting in different eye colors.

Still, even if genetics can determine whether an individual will have heterochromia, it isn’t the absolute deciding factor.

What are the Different Types of Heterochromia?

There are three different types of heterochromia, namely: 

• Central heterochromia
• Complete heterochromia
• Sectoral heterochromia

How Common is Central Heterochromia?

Central heterochromia is less common compared to complete heterochromia. The exact prevalence rate is unknown, but it’s estimated to occur in a very small percentage of the population.

Central heterochromia is an eye color condition where the human iris’s inner area is different from the outer area. This causes two ring colors within the same iris.

To illustrate, someone with central heterochromia can have a blue outer iris with a ring of green or brown around the pupil.

What is Complete Heterochromia?

Complete heterochromia is a condition where someone has two different eye colors. While most people have the same eye color for both eyes, an individual with this condition can have one eye that is blue and another brown, which creates a striking contrast.

This is considered a rare condition and affects fewer than 200,000 Americans, or about six out of every 10,000 people, according to the National Institutes of Health (NIH).

What Distinguishes Sectoral Heterochromia?

Sectoral heterochromia is a condition where a section of the iris has a different color from the rest of the iris.

Unlike central heterochromia, where there is a ring around the iris or spikes of colors radiating from the iris, sectoral heterochromia has a part of the iris that is a different color from the rest.

For instance, you could have blue eyes, but if someone were to look at your eyes closely, there might even be a splash of green or brown in your iris. This happens because of how pigments are distributed in the iris.

Sectoral heterochromia can affect one or both eyes. It is unknown how rare this condition is, but it is considered to be more rare than complete heterochromia.

What Causes Heterochromia?

Heterochromia can develop due to the following factors:

• Genetics
• Melanin production and distribution
• Other factors such as eye injury, surgery, and medications

Can Heterochromia Develop Due to a Genetic Condition?

Heterochromia can develop due to a genetic condition.

Genes contribute to determining eye colors, and mutations of certain genes can result in heterochromia. Here are some specific genetic conditions that can result in a person having different eye colors:

• Waardenburg Syndrome – This genetic condition can affect a person’s skin, hair, and eye color. Someone with Waardenburg syndrome can have heterochromia because of the changes in the amount and type of pigments in the iris.³ This happens due to the mutation in certain genes like Paired Box 3 (PAX3) and Melanocyte Inducing Transcription Factor (MITF), which assist in making pigments and controlling their development.
• Noonan Syndrome – This condition sometimes results in someone having different eye colors. It occurs due to the mutations in various genes which play roles in cell growth and development. While its association with heterochromia is not as prevalent as Waardenburg syndrome, the genetic mutations in Noonan syndrome can affect various aspects of development, including pigmentation.
• Piebaldism – Similar to Waardenburg syndrome, this genetic condition is characterized by patches of depigmented (white) skin and hair, along with risk factors of heterochromia. Receptor Tyrosine Kinase (KIT gene) mutations are usually responsible for Piebaldism.
• Parry-Romberg Syndrome – Some people with Parry-Romberg Syndrome might also have different eye colors or heterochromia.
• Sturge-Weber Syndrome – A rare disorder marked by facial port-wine stains, neurological complications, and ocular manifestations, including heterochromia, where people may have different eye colors.

How Does Melanin Influence Heterochromia?

A pigment called melanin is responsible for the color of skin, hair, and eyes, influencing eye color.

Melanin is created in specialized cells called iris melanocytes.² The amount and type of melanin present in the front layer of the iris, known as the iris stroma, largely determine eye color.

The two main types of melanin are eumelanin, which is brown to black in color, and pheomelanin, which is red to yellow. The interaction between eumelanin and pheomelanin and the amount of melanin present defines the spectrum of eye colors, ranging from blue eyes to green to brown.

The presence, distribution, and concentration of melanin in the irises have an impact on eye color. If there is a genetic variation that affects the production or distribution of melanin in the irises, it can result in having different-colored eyes or sections of varying colors within the same human iris.

What Other Factors Can Lead to Heterochromia?

If a person gets heterochromia later in life, it is called acquired heterochromia. Some factors that can lead to this include:

• Eye injury or trauma
• Bleeding in the eye
• Swelling in the eye due to uveitis or iritis
• Eye surgery
• Fuchs’ heterochromic cyclitis
• Acquired Horner’s syndrome
• Glaucoma and some glaucoma eye drops
• Pigment dispersion syndrome
• Ocular melanosis
• Posner-Schlossman syndrome
• Iris ectropion syndrome
• Iris tumors
• Diabetes
• Central retinal vein occlusion
• Chediak-Higashi syndrome

Complications and Concerns with Heterochromia

Does Heterochromia Affect Vision?

Often, heterochromia doesn’t affect eye health, which means it doesn’t affect someone’s vision.

Primarily, it affects eye color and not eye function. People with heterochromia usually have normal vision, like those with eyes of the same color.

However, in some cases where heterochromia is associated with specific underlying conditions such as uveitis, glaucoma, or iris tumors, it can affect eye health.

Moreover, genetic conditions that can cause heterochromia and impact eye health can potentially impact someone’s vision.

If heterochromia results from eye injury, it can also affect one’s vision.

Can Heterochromia be Harmful?

If an infant is born with heterochromia or acquires it right after birth (congenital heterochromia), it is generally not harmful and is rarely telling of an underlying health problem.⁴

On the other hand, acquired heterochromia can be due to a wide range of factors, such as eye injuries, eye diseases, surgeries, or certain medical conditions that can affect eye health and vision.

Heterochromia is simply a difference in eye color and is usually an aesthetic trait that does not have negative health implications. Those with this eye condition generally have normal vision and eye health, just like people with the same color for both eyes.

However, if your eye color changes come with changes in vision, discomfort, or any other unusual symptoms, it’s recommended to consult with an eye care professional for accurate evaluation and guidance.

Common Questions About Heterochromia

Can Heterochromia Appear at Any Age?

Heterochromia can appear at any age.

An infant can be born with it, or someone can develop heterochromia later in life for several reasons, including eye surgery, certain diseases, medications, or other health conditions.

How Rare is Heterochromia?

It is rare to meet someone with different eye colors or have a splash of different colors within the same eye. In fact, heterochromia affects fewer than 200,000 Americans or about six out of every 10,000 people.

Can You Have Heterochromia If Your Parents Don’t?

Heterochromia occurs due to the pigment variations in a person’s eyes.

While it can be hereditary, it’s most often not inherited. Therefore, it’s possible to have this condition even if your parents don’t.  

Is Heterochromia Considered a Birth Defect?

Someone born with congenital heterochromia will generally experience no other symptoms. Therefore, it’s not a birth defect. It is primarily a difference in eye color, which is often cosmetic. While heterochromia can be because of genetic factors or other conditions, it doesn’t generally come with functional limitations or health problems.

How is Heterochromia Diagnosed and Treated?

It’s a good idea to see an eye doctor or ophthalmologist for acquired heterochromia with a potential underlying condition. 

They can carefully perform an eye exam to determine any reason behind the difference in eye color and make a plan to help if needed. Treating heterochromia means focusing on dealing with whatever might be causing it in the first place, which your doctor can help you with.