Heterochromia: Genetic or not?

Is heterochromia genetic?

Heterochromia is a condition that causes one or both eyes to be different colors. Heterochromia has many causes and can occur at birth or be acquired later in life. Although it is rare, the condition can be hereditary. It depends on very specific genes.

Heterochromia can occur in one of three varieties: 

• Complete heterochromia – Each iris is a different color.
• Partial (sectoral) heterochromia – The iris has multiple colors in one eye.
• Central heterochromia – The iris has an outer ring of color and an inner ring of color that are different in hue. 

The color or color pattern is distinctive to each individual eye. And it’s usually benign.

Heterochromia is often present from birth due to a genetic variation in someone’s DNA or a non-inherited congenital condition such as Horner’s syndrome. New or changing heterochromia at any age, and especially in adults, should be checked by an eye doctor.

How heterochromia can be inherited

Heterochromia can be inherited, but it depends on specific genetic makeup.

For example, heterochromia can be inherited or occur through a random genetic mutation. It can also develop as a result of underlying genetic conditions.

But most cases of heterochromia occur sporadically, and the condition doesn’t usually run in families. In other words, the trait may develop genetically but it often occurs sporadically.

Is heterochromia a dominant or recessive trait?

Is heterochromia a genetic condition? And if so, is it dominant or recessive? 

Heterochromia can sometimes be inherited due to a genetic mutation in one or both parents’ DNA. In many (but not all) genetic cases, the mutation is autosomal dominant.  

Heterochromia can be caused by a random genetic mutation

Is heterochromia genetically inherited? You can inherit a genetic mutation from one of your parents that affects how much melanin you produce or a change to the genes can happen randomly without being passed down from a parent. (Melanin is a pigment responsible for hair, skin and eye color.) 

Your eye color depends on how much or how little melanin you have. When the genes that affect melanin are mutated, it can cause different eye colors (heterochromia).

Genetic disorders can also cause heterochromia

Though heterochromia itself is seldom inherited, it can develop secondarily to a genetic condition. But these causes are rare by comparison.

Some genetic conditions that may cause heterochromia to develop include:

• Tuberous sclerosis (Bourneville disease)
• Bloch-Sulzberger syndrome (also referred to as incontinentia pigmenti)
• Piebaldism
• Waardenburg syndrome

SEE RELATED: What causes heterochromia?

Other risk factors for heterochromia

Different eye colors can appear congenitally (meaning they occur at birth). But congenital conditions are not always genetic.

Non-genetic, congenital causes of heterochromia can include:

• Parry-Romberg syndrome (PRS)
• Sturge-Weber syndrome (SWS)
• Congenital Horner’s syndrome

Heterochromia can also be acquired under certain circumstances, such as:

• Some forms of glaucoma 
• Glaucoma medication 
• Chronic use of bimatoprost eyelash serum (main ingredient is commonly used as a glaucoma medication; now also used cosmetically to enhance eyelashes)
• Eye injury or trauma
• Eye surgery
• Diabetic eye disease
• Tumors of the iris/ocular melanoma
• Swelling brought on by uveitis or iritis
• Acquired Horner’s syndrome

Horner’s syndrome is the result of nerve damage on one side of the face. This nerve damage can disrupt melanin production, causing less melanin production in the iris on the side of the face with nerve damage. Less melanin can mean a lighter eye color on this affected side. For this reason, the presence of heterochromia in infants should be promptly evaluated. This condition can be congenital or acquired.

That being said, these causes are rare by comparison.

Is heterochromia a genetic disorder?

As a reminder, heterochromia can have a genetic component and be present at birth or develop at any stage in life. Your eye doctor can help determine the primary cause of heterochromia upon diagnosis. 

If you notice a change in your eyes’ color or appearance, don’t hesitate to schedule a comprehensive eye exam with an eye care professional near you.

RELATED READING: The genetics of eye color