Genetic Albinism is an inherited and congenital disorder that is characterized by partial and complete loss of pigmentation of the skin, eyes, and hair. The controversial gene-related condition is often unpredictable, leading to numerous queries such as “ is albinism a genetic disorder? What genes cause albinism? How is albinism passed down? And most disturbingly, does albinism run in the family?
What is Albinism really? And how is albinism diagnosed? People with this disease are called albinos and they have low levels of melanin which is the primary pigment responsible for the coloration of the eyes (ocular albinism), skin and hair.
Albinos have lighter skin and hair color that is distinctively different from that of their family members or ethnic group. The debilitating effects of this disorder include vision loss and extreme sun-sensitivity. Melanin functions to protect the skin from harmful ultraviolet rays. The lack or low levels of melanin in albinos make them more susceptible to the harmful UV radiation of the sun.
Albinism facts – melanin deficiency in albinos also impairs their vision and is responsible for their distinct eye colors. The iris of the eye contains melanin which blocks and protects against certain lights including sunlight. With albinism, the photoreceptors in the iris become saturated with light which passes on the wrong signal to the brain and causes the eye to flutter (nystagmus) or function in opposite directions (cross-eye or strabismus).It also makes the eye extremely sensitive to light, this is known as photosensitivity.
The pupils of the eye are naturally colored black because the melanin in the retina absorbs light that enters the eye. In albinos with little to no melanin in their eyes, the retina reflects back the color of the light entering the eyes and causes the iris to take on colors like red or pink.
CAUSES AND TYPES OF GENETIC ALBINISM
Genetic mutations are primarily responsible for the occurrence of albinism. They interfere with the functions of a cell called melanocyte that produces melanin. The melanocytes are present in albinos, but genetic mutations hinder their ability to produce the pigment or distribute it to skin cells called keratinocytes which are found in the outer layer of the skin (the epidermis).
There are five types of genetic albinism that have been currently identified, and the most common is oculocutaneous albinism. This is categorized into several types to include OCA type 1,2,3, and 4, of which type 1 and 2 is the most prevalent. OCA1 is caused by mutations in the TRY gene that encodes the tyrosinase enzyme. The enzyme is required by melanocytes to produce melanin from tyrosine(an amino acid). OCA2 is caused by mutations of the OCA2 gene that codes the P protein. The function of the P protein is yet to be known. Albinism can also result from problems with other genes such as TYRP1, HPSI, and SLC45A2. Other types of albinism include :
X-linked ocular albinism: Caused by gene mutation of the X chromosome. It is most prevalent among males and it causes vision defects.
Chediak-Higashi syndrome: A rare type of albinism caused by gene mutation of the CHS1/LYST genes. People with this type of albinism may have silvery hair and grayish skin. They are also prone to infections as the condition may cause problems with the white blood cells.
Hermansky-pudlak syndrome: Presents the normal range of albinism symptoms but bleeding disorders and diseases of the heart, kidney, lungs, and bowel may occur. It is a rare form of albinism that is most prevalent in Puerto Rico.
Griscelli syndrome: The rarest variant of albinism that is caused by mutations in one of three genes. It is associated with immune and neurological problems and is known to cause death within the first decade of life.
THE ROLE OF INHERITANCE IN GENETIC ALBINISM
Inheritance plays a key role in the development of albinism. It is believed that about one in 70 people is carriers of albino genes. A person may carry defective genes without presenting any symptoms. Defective albino genes are usually passed from parents to children through the autosomal recessive inheritance pattern with the exception of ocular albinism which is passed on in an X-linked inheritance pattern.
In autosomal recessive inheritance, a defective gene must be passed on from both parents to the child for albinism to develop. The child will not develop albinism if the gene is passed on from just a single parent. The carrier is usually asymptomatic.
In x linked recessive inheritance pattern, the albino gene is passed on through the X chromosome and it often affects men. This is because men have only one x chromosome while women have two. What this means is that, once the gene is present on the X chromosome of men, the chances of developing albinism is high. For women, the presence of the defective gene on one of their x chromosomes will only increase their chances of becoming a carrier without necessarily developing symptoms of the condition.
THE NEED FOR A CURE
Albinism has devastating effects on an individual’s life. Aside from the debilitating health conditions associated with the disease, day to day living can be a challenge for an albino as they struggle to avoid the sun or contend with an impaired vision. Exposure to the sun can increase their risk of developing cancer. Albinos are especially at risk of developing squamous cell carcinoma and basal cell carcinoma, cancers that affect the outermost and deeper layers of the skin respectively.
There is also the issue of societal discrimination and stigma against albinos in some parts of the world because of their skin color. Standing up against societal prejudice and stigmatization can be depressing for an individual with albinism. There have been horrifying reports of albinos being used killed and used for fetish rituals in Tanzania.
The perpetrators of this inhumane act believe that the body parts of albinos have magical powers that can bestow riches. In some parts of Zimbabwe and Tanzania, mating with an Albino woman is believed to be a permanent cure for AIDS, this ignorant belief has led to higher cases of rape and AIDS in the said countries with albinos at the receiving end. These are some of the reasons why albinism needs to be eradicated from society at large to prevent further suffering and alienation. But unfortunately, genetic albinism currently has no cure.
Most science has been able to offer are treatment options that can manage the effects of the debilitating condition. Prescription glasses and routine eye checks are recommended to manage vision problems. For nystagmus and strabismus, surgery to minimize the symptoms may be recommended. To protect against sunburn and skin cancer, they are advised to use sunscreen and have limited exposure to the sun. But all of these do not provide a lasting solution to their problems. This brings us to the bigger question “is there hope for a cure?”
CAN SCIENCE CURE GENETIC ALBINISM?
If albinism were to be caused by a microorganism such as a virus or bacteria, then perhaps finding a cure wouldn’t be so hard. But scientists have had a hard time finding a permanent solution to the disease because it is a genetic disorder. The truth is, to eliminate albinism, the occurrence of albino genes needs to be stopped. However, scientists have refused to allow this genetic barrier to deter them in their quest for a cure. They have continued to carry out genetic albinism experiments and research work unperturbed.
A clinical pilot study led by the clinical director of the National Eye Institute(NEI) , Brian Brooks has unveiled a potential treatment for hair and vision problems in people with albinism through the use of nitisinone drugs. Currently the treatment options available for hair, skin and vision defects associated with albinism only minimize the symptoms. The research suggests that drug Nitisinone can increase melanin production in people with OCA type 1. Increased production of melanin in people with this type of genetic albinism can protect them against the damaging effects of the sun’s UV rays and improve their vision to a great degree.
Nitisinone is an FDA-approved drug used in the treatment of certain blood conditions known as hereditary tyrosinemia type 1, where it increases eye and hair pigmentation from generating tyrosinase protein. The researchers built their experiment around nitisinone due to its effect on tyrosinase which is the enzyme that is dysfunctional in people with OCA type 1. For the study, people with OCA type 1B were targeted because they have some tyrosinase whose function (to influence the production of melanin) is impeded by albino genes. Whereas, people with OCA-1A completely lack tyrosinase.
The study participants which included two men and three women were given a daily oral dose of 2mg of nitisinone over a 12 month period. The dosage was then stopped for another six months. Skin and hair darkening was observed in most of the participants while on nitisinone. One particular participant showed slight skin darkening after being exposed to the sun.
However, little to no visual improvement was observed, but scientists believe that vision problems can be addressed in younger participants with the use of nitisinone. since the eye undergoes developmental changes during the early stages of life and through teenage years,they can bank on this to find a potential cure for vision defects in younger children with OCA-1B.
Another group of researchers from kobe University has found an easier way to produce precursor melanocyte cells through stem cell technology.There are already several methods used to generate melanocytes from stem cells,but these methods are difficult, time consuming and costly. However, these team of researchers generated melanocytes by freezing and defrozing the cells and administering activators that sped up their growth in as little as one week.
This way melanocytes can now be produced in large amounts within a short period of time. This method has made it easy for researchers to obtain melanocyte samples from patients suffering from melanocyte disorders such as albinism and from healthy donors. These samples can be applied in all areas of melanoma and melanocyte disorder research including albinism. With precursor melanocytes which is an important factor in the disease development of albinism at their disposal, scientists are one step further in their search for a cure.
Most mutating genes linked to albinism are yet to be identified, but a recent study by a team of UC Davis researchers has solved this mystery by identifying dozens of these genes in knockout mice. The researchers hope that this new information will serve as a resource for scientists studying genetic disorders.
The quest for a cure continues, and the world is hopeful that science will defeat genetic albinism through gene therapy and other methods in the near future.