Keratoconus is often associated with other diseases, particularly those that affect the connective tissue. Keratoconus has been associated with atopic diseases, which include asthma, allergies, and eczema, and it is not uncommon for several or all of these diseases to affect one person. Keratoconus is also associated with Alport syndrome, Down syndrome, Ehlers-Danlos syndrome (EDS), and Marfan syndrome.
The exact relationship between keratoconus and these other diseases is not fully understood. It is possible that they share common genetic or environmental risk factors. For example, both keratoconus and Ehlers-Danlos syndrome are caused by defects in the connective tissue. It is important to note that not everyone with keratoconus will have another associated disease.
Atopic diseases:
Atopic diseases are a group of chronic inflammatory conditions that are caused by an overreaction of the immune system to allergens. The most common atopic diseases are asthma, allergic rhinitis (hay fever), and atopic dermatitis (eczema).
There is a growing body of evidence that suggests that atopic diseases and keratoconus may be associated. For example, a study published in the British Journal of Ophthalmology found that people with keratoconus were more likely to have a history of atopic diseases than people without keratoconus. Additionally, a study published in the Investigative Ophthalmology & Visual Science found that people with keratoconus had higher levels of immunoglobulin E (IgE), an antibody that is associated with allergic reactions.
The exact mechanism of the association between atopic diseases and keratoconus is not fully understood. However, there are a few possible explanations. One possibility is that atopic diseases may cause inflammation in the cornea, which can lead to thinning and bulging. Another possibility is that people with atopic diseases may be more likely to rub their eyes, which can also damage the cornea.
The association between atopic diseases and keratoconus has a number of clinical implications. It is important to be aware of this association in order to diagnose keratoconus early. This is because early diagnosis and treatment can help to prevent vision loss.
Patients with atopic diseases should be counseled on the importance of avoiding eye rubbing. Eye rubbing can further damage the cornea and accelerate the progression of keratoconus.
Down syndrome:
Down syndrome (DS) is a genetic disorder caused by the presence of an extra chromosome 21, either fully or partially. It is the most common chromosomal abnormality in humans. People with DS have a number of characteristic physical features, including intellectual disabilities, developmental delays, and distinctive facial features.
People with DS have a much higher risk of developing keratoconus. Studies have shown that anywhere from 5% to 30% of people with DS also have keratoconus. This is a significant increase in risk, and it is important for people with DS to be aware of the condition and to get regular eye exams to detect it early.
The exact reason for the association between DS and keratoconus is not fully understood. However, researchers believe that it may be related to a number of factors, including:
Collagen abnormalities: People with DS have an increased risk of developing certain types of collagen disorders. Collagen is a protein that is found in many parts of the body, including the cornea. Abnormalities in collagen can weaken the cornea and make it more susceptible to keratoconus.
Eye rubbing: People with DS are more likely to rub their eyes excessively. This can damage the cornea and increase the risk of developing keratoconus.
Atopy: Atopy is a group of allergic conditions, such as asthma, eczema, and hay fever. People with DS are more likely to have atopy. Studies have shown that there may be a link between atopy and keratoconus.
Genetic factors: Some studies have suggested that there may be a genetic link between DS and keratoconus. However, more research is needed to confirm this link.
Marfan syndrome:
Marfan syndrome (MFS) is a genetic disorder of connective tissue that can affect many parts of the body, including the heart, lungs, blood vessels, eyes, and bones. It is caused by a mutation in the FBN1 gene, which produces a protein called fibrillin-1. Fibrillin-1 is an important component of connective tissue, which provides strength and support to many organs and tissues.
There is a small but significant association between MFS and keratoconus. Studies have shown that people with MFS are more likely to develop keratoconus than the general population. The exact nature of this relationship is not fully understood, but it is thought to be related to the same genetic mutations that cause MFS.
One possible mechanism for the association between MFS and keratoconus is that the genetic mutations that cause MFS can also affect the development and structure of the cornea. The cornea is made up of several layers of tissue, including a layer of collagen called the stroma. Collagen is a type of protein that gives the cornea its strength and shape. The genetic mutations that cause MFS can weaken the structure of collagen in the cornea, making it more likely to thin and bulge.
Another possible mechanism for the association is that the cardiovascular problems associated with MFS can also affect the cornea. MFS can cause the aorta, the main artery in the body, to weaken and enlarge. This can lead to a condition called aortic aneurysm, which can put pressure on the optic nerve, which carries visual signals from the eye to the brain. Pressure on the optic nerve can damage it and lead to vision loss.
Sleep apnea
Sleep apnea is a sleep disorder in which breathing repeatedly stops and starts during sleep. Obstructive sleep apnea (OSA), the most common type of sleep apnea, occurs when the throat muscles relax and block the airway during sleep. This can lead to a variety of health problems, including cardiovascular disease, stroke, and diabetes.
Researchers have found that people with keratoconus may be 10 to 20 times more likely to suffer from the sleep disorder known as obstructive sleep apnea than those without keratoconus. A 2015 study published in the British Journal of Ophthalmology found that people with keratoconus were 1.8 times more likely to have sleep apnea than people without keratoconus. Another study found that people with keratoconus were 10 times more likely to have sleep apnea than people without keratoconus.
Ehlers-Danlos syndrome:
Ehlers-Danlos syndrome (EDS) is a group of genetic disorders that affect connective tissue, the protein that provides support and structure to the skin, bones, and organs. There are 13 recognized types of EDS, each caused by a mutation in a different gene.
There is a growing body of evidence to suggest that EDS and keratoconus are associated. For example, a 2022 study found that people with keratoconus are five times more likely to have EDS than the general population. Additionally, people with EDS are more likely to have certain genetic mutations that are also associated with keratoconus.
The exact reason for the association between EDS and keratoconus is not fully understood, but it is thought to be due to the fact that both conditions involve defects in the connective tissue. The connective tissue in the cornea is responsible for maintaining its shape and strength. When the connective tissue in the cornea is weak, it can lead to the development of keratoconus.
The treatment for keratoconus in people with EDS is the same as the treatment for keratoconus in people without EDS. However, it is important to note that people with EDS may be more at risk for complications from certain treatments, such as corneal collagen cross-linking (CXL) and intracorneal ring segments (ICRS). Therefore, it is important to discuss all treatment options with an eye doctor who is experienced in treating people with EDS.
Alport syndrome:
Alport syndrome is a rare genetic disorder that affects the kidneys, eyes, and ears. It is caused by mutations in genes that code for collagen type IV, a protein that is essential for the structure and function of these tissues.
The most common symptoms of Alport syndrome are kidney disease, hearing loss, and eye abnormalities. Kidney disease is the most serious complication of Alport syndrome and can lead to end-stage kidney disease. Hearing loss typically begins in childhood and can progress to deafness. Eye abnormalities can include anterior lenticonus (a bulging of the front of the lens), posterior polymorphous corneal dystrophy (a type of corneal dystrophy), and fleck retinopathy (small white spots on the retina).
There is a growing body of evidence to suggest that keratoconus and Alport syndrome may be associated. In a study published in 2023, researchers found that 6.7% of patients with Alport syndrome also had keratoconus. This is significantly higher than the prevalence of keratoconus in the general population.
The exact reason for the association between Alport syndrome and keratoconus is not fully understood. However, it is thought that the mutations in collagen type IV that cause Alport syndrome may also make the cornea more susceptible to thinning and bulging.