Oculocutaneous albinism type 2 is the most common variant of albinism worldwide, affecting the skin, hair and eyes. The phenotypic manifestation of the disease covers a wide range, ranging from barely visible to complete albinism. The visual impairments associated with this type of albinism also vary.
What is oculocutaneous albinism type 2?
The main phenotypic symptom that accompanies all forms of oculocutaneous albinism type 2 (OCA2) is largely unpigmented skin. Another feature is the hair color, which in some cases can be blonde or even brown, which is known as brown OCA. Because those affected can also have blond hair, the disease often goes undetected in Scandinavian residents. See acronymmonster for Definition of Hematopneumothorax in English.
Because the skin color does not differ from that of particularly light-skinned Scandinavians, especially since the iris of the eyes can also take on a brown to blue-green coloration. The visual defects often associated with OCA2 are limited visual acuity and very high sensitivity to light. The loss of a large part of the pigmentation is attributed to an incorrectly encoded membrane protein of the melanosomes.
Similar to lysosomes, melanosomes are functional organelles in the pigment cells. They synthesize melanin in the melanocytes of the epidermis and in the pigment epithelial cells of the iris. A genetic defect causes the enzyme tyrosinase, which is involved in the formation of melanin from tyrosine, to malfunction.
The skin pigment melanin is produced by a specific type of skin cell called melanocytes. The cells are located in the basal layer of the epidermis. The dye is formed from tyrosine in special cell organelles, the melanosomes, and released to horny cells (keratinocytes), which migrate to the surface of the skin within 28 days and are shed there as tiny scales.
The formation of melanin from tyrosine in the melanosomes requires the enzyme tyrosinase, which is produced in the endoplasmic reticulum. To cross the membrane that encloses the melanosome, the tyrosinase depends on a special transport protein, the so-called P protein. The P protein is encoded by the so-called P gene, which is located on the long arm of chromosome 15 (gene locus 15q11-13).
A mutation in intron 1 of the P gene leads to an incorrect coding of the P protein with extensive loss of function. As a result, the tyrosinase that is urgently needed in the melanosomes cannot cross the membrane and is instead excreted or metabolized beforehand. Ultimately, the incorrectly encoded P protein results in insufficient melanin production. OCA2 is inherited in an autosomal recessive manner. This means that both parents must have the same genetic defect for the disease to occur.
Symptoms, Ailments & Signs
The most striking symptom that appears in type 2 oculocutaneous albinism is the reduced supply of the skin with the pigment melanin. This is not a complete loss of pigment, but a “basic pigmentation” is retained. This means that those affected have a lighter skin color than healthy people.
However, this symptom is less noticeable in fair-skinned Scandinavians, especially in winter, so the symptoms can be overlooked in them. Affected people often later develop clearly visible pigment spots on the skin, so-called naevi. Since the cause of OCA2 cannot be triggered by a uniform gene defect, but by different gene mutations, the occurrence of symptoms and signs also varies. Above all, the visual impairments vary in severity.
Diagnosis & course of disease
Oculocutaneous albinism type 2 is caused exclusively by mutations in the P gene. No other causes such as contact with pollutants, infections suffered or exceptional psychosocial problems are considered. The course of the disease requires certain protective measures against direct sunlight, namely for the eyes and for the skin.
The eyes are usually very sensitive to sunlight, and the skin is only insufficiently protected against sunburn by melanin. Ultimately, a clear and reliable diagnosis can only be made by means of a molecular genetic examination.
In oculocutaneous albinism type 2, the pigment melanin is missing in the skin, so the skin protection is lost. The only way to avoid complications is therefore to use adequate sun protection for the eyes and skin. Sun glasses should be worn at all times to protect the eyes. Otherwise there is a dramatic reduction in visual acuity, which can lead to blindness. Sometimes eye tremors or strabismus (squinting) are also observed.
In addition to eye protection, existing vision problems must be compensated for with special glasses or contact lenses. In some cases, the lens may need to be surgically replaced to prevent blindness. To protect the skin, sun protection products that have a strong UV filter should always be used. Otherwise, there is a great risk of developing skin cancer.
In most cases, multiple basalioma (white skin cancer) form. These are semi-malignant skin tumors that do not lead to death, but to the complete destruction of the surrounding tissue. Spinalioma, a so-called squamous cell carcinoma, can develop as the second most common form of skin cancer. In addition to severe tissue destruction, metastases also form in distant body regions.
However, the most dangerous is the so-called melanoma (black skin cancer), which forms metastases very quickly and can affect all organs of the body. Patients with type 2 oculocutaneous albinism should therefore be regularly examined for skin tumors.
When should you go to the doctor?
Oculocutaneous albinism type 2 is not a pigmentary disorder that requires treatment. In Scandinavia, where fair skin and blonde hair are normal, type 2 oculocutaneous albinism often goes undetected. However, the associated sensitivity to light and the risk of developing skin cancer from UV rays are risks that make regular visits to the doctor necessary. The eye diseases associated with albinism can also make a visit to the ophthalmologist necessary.
Protection of the unpigmented skin and sensitive eyes is a priority when oculocutaneous albinism type 2 has been diagnosed. Sunglasses should be worn at all times, even when the sky is cloudy. Otherwise there is a risk of blindness. Sun creams should have the strongest sun protection factor. A doctor should regularly examine the skin for nevi, or signs of skin cancer. Basal cell carcinomas frequently occur in oculocutaneous albinism type 2.
Treatment & Therapy
Treatment options for OCA2 are essentially limited to treating the symptoms and protective measures that are suitable for effectively protecting the eyes and skin from the UV component of sunlight. Sunscreen and sunglasses should be able to block or filter out a sufficiently high UV component of sunlight. For long stays in tropical and subtropical countries, clothing that offers proven UV protection is recommended.
Special attention should be paid to the eyes because in many cases the fovea centralis, the tiny zone of sharpest vision, suffers from a lack of melanin, which can lead to impaired visual acuity. If insufficient UV protection of the eyes leads to premature clouding of the lens, which is similar to cataracts, vision can be restored by surgically replacing the lens.
Outlook & Forecast
Type 2 oculocutaneous albinism is not life-threatening, but it is often a life-affecting, hereditary pigmentation disorder. This represents the more common form of albinism. The affected people are completely white-skinned. You have white-blonde hair due to a disorder in melanin formation, melanosome formation or transfers of melanosomes.
Those affected are more susceptible to skin cancer because of the lack of pigmentation in the skin. Otherwise, those affected often suffer lifelong stigmatization because of their light hair and skin color and increased sensitivity to light. The degree of social exclusion depends on the region in which they live. The level of information about albinism also plays a role. In some tribes in Africa, the inheritance rate is significantly higher. Albinism is not considered uncommon there.
The prevalence of oculocutaneous albinism type 2 can be as high as 1/1,500 in some tribes. In comparison, the frequency of occurrence in other countries is 1:15,000 or 1:20,000 births. Type 2 oculocutaneous albinism is common among the Hopi or Navaho Indians. Some albinos in Africa have dark brown patches on their skin called naevi. The overall prognosis is good. Such people can live to a ripe old age if they protect themselves from UV radiation. The prognosis becomes worse if Prader-Willi syndrome or Angelman syndrome occur concomitantly.
Preventive measures that could prevent the autosomal recessive inherited oculocutaneous albinism type 2 do not exist. However, preventive measures are recommended to reduce the risk of developing side effects. Regular dermatological examinations of the skin are primarily indicated because of the increased risk of skin cancer from sun exposure.
Regular examinations increase the chance that developing skin cancer can be detected and treated at an early stage. Equally important is effective UV protection for the eyes in order to minimize the risk of developing cataracts at an early stage.
Basically, follow-up care is necessary to ensure that the disease does not recur in the future. Oculocutaneous albinism is considered incurable. Therefore, medical support cannot be the goal. Instead, appropriate aftercare should help the patient to manage everyday life and prevent complications. In the case of acute symptoms, those affected consult a doctor.
Regular check-ups are the exception rather than the rule for albinism. When the diagnosis is made, patients receive comprehensive information about the effects of albinism. Appropriate skin protection is considered a preventive measure of aftercare treatment. Those affected must avoid direct sunlight.
UV radiation is at its highest around midday in particular, and sunscreen with a high sun protection factor is strongly recommended. People with albinism often also suffer from poor eyesight. Glasses can bring relief here. A very light and pale skin is considered characteristic and psychological follow-up is therefore advisable.
Young people in particular often find their appearance very stressful. The exclusion of people of the same age because of being different occurs again and again. Some patients also complain about disadvantages at work. Thanks to psychological therapy, anxiety disorders and depression can be prevented prematurely. Such therapy can be prescribed by a doctor.
You can do that yourself
So far, there are no adequate treatment methods, which is why it is mainly the person affected who has to take action themselves. This includes observing the skin for the smallest changes and regular dermatological examinations by a specialist. This allows possible skin cancer to be detected at an early stage. The earlier this happens, the more effective and less invasive subsequent treatment will be.
Since fair skin is very sensitive to the sun’s rays, suitable sun protection must be used every day all year round. This can be done in many ways and depends largely on the current sensitivity of the skin. For all parts of the skin that are permanently exposed to daylight, such as the face, neck and hands, sunscreen with a sun protection factor of 50 and higher from the pharmacy is recommended. In order to protect the eyes and lips adequately, it is essential to ensure that sunglasses and lip balms have a UV filter.
There are a few things to keep in mind when it comes to clothing. In principle, every piece of clothing protects the skin it covers from UV radiation, but the density of the fabric determines the extent of this protection. Particularly tightly woven clothing or UV protective clothing offers the greatest possible protection. Appropriate headgear should not be forgotten, of course.
In everyday life, products such as UV-hardening nail polish should be avoided, as should visiting a conventional solarium.