Many people want to know if they are susceptible to a disease that a parent has or if they may potentially pass a condition on to a child.
If a disease is inherited, it is because it is a genetic condition.
Types of Genetic Conditions
There are many different types of genetic conditions based on how they are passed on to children.
Not all conditions are entirely genetic, some only have a genetic component.
Of conditions that are entirely determined by genetic inheritance, there are four different types of diseases.
Autosomal dominant, autosomal recessive, and mitochondrial inheritance conditions do not affect a gender more than the other.
X-Linked conditions will affect males more than females.
Autosomal Dominant Conditions
If a condition has autosomal dominant inheritance, it will affect all of the people who inherit it. These types of conditions will be more prevalent than some other genetic disease because everyone with the gene will have the disease.
Autosomal Dominant Conditions of the Eyes
Eye conditions that are inherited as autosomal dominant include corneal dystrophies such as epithelial basement membrane dystrophy or Fuch’s endothelial dystrophy, keratoconus, cystoid macular edema, Stargardt’s Disease, tuberous sclerosis, and Von Hippel Lindau Syndrome.
Many of these conditions are severe and can affect vision at an early age.
There are also many autosomal dominant conditions that affect the entire body and have serious ocular involvement or effect. These include neurofibromatosis, Ehlers-Danlos Syndrome, Marfan Syndrome, and osteogenesis imperfecta.
There are other conditions which are autosomal dominant but either are extremely rare or have little impact on the eyes.
Autosomal Recessive Conditions of the Eyes
Conditions that are autosomal recessive may present as the full condition and cause symptoms or may only result in an individual being a carrier of the trait without any symptoms.
These conditions frequently surprise families as there is not a direct known relative with the condition in full.
Eye conditions that are inherited as autosomal recessive include oculocutaneous albinism, pseudoxanthoma elasticum, cone dystrophy, and Tay Sachs disease.
Like autosomal dominant diseases, there are also many conditions that are not exclusive to the eyes which are autosomal recessive.
Among the most common are cerebral palsy, homocystinuria, sickle cell anemia, and Wilson disease.
Since autosomal recessive conditions tend to occur less than autosomal dominant conditions, many more exist but are very rare.
Mitochondrial Inheritance Conditions of the Eyes
Unlike autosomal dominant and recessive conditions, mitochondrial inheritance conditions are only passed maternally with the mitochondrial DNA.
Because of this, an affected mother will pass this condition to all of her children.
The most prevalent mitochondrial inheritance disorder in the eyes is Leber’s Hereditary Optic Neuropathy.
This condition is most common in the regions of Scandinavia and the descendants of that region.
X-Linked Inheritance
Genetically, everyone inherits two sex chromosomes – one from each parent. In females, there are two “X” chromosomes and in males there is one “X” and one “Y” chromosome.
This difference causes the biological differences between the sexes and allows for X-linked inheritance patterns.
In this type of disease, the condition is carried on an X chromosome. In females, if only one “X” chromosome is affected, they will not have the condition.
However, in males, if the only “X” chromosome is affected they will have the condition.
X-Linked Inheritance Conditions of the Eyes
There are fewer X-linked conditions than autosomal conditions in general, however there are several which are relevant to the eyes.
Major X-linked conditions in the eyes are retinitis pigmentosa, color blindness, Fabry disease, and megalocornea.
Importance of Understanding the Role of Genetics in Eye Diseases
In all, the diseases above count for only a small portion of the total number of eye conditions which are genetic in nature.
Additionally, many diseases – including glaucoma and macular degeneration – have a genetic component but are not entirely genetic diseases.
Because of the vast number and severity of these diseases, it is important to educate yourself on the conditions that may run in your family.
