What is Albinism?
Albinism is a group of heritable diseases associated with absent or decreased melanin in ectoderm-derived tissues such as skin, hair, nails, hooves, eyes, causing a decrease in skin pigmentation.
Melanin is a natural skin pigment that plays a great role in determining the colour of the skin, and hair and in the development of certain optical nerves. When the body lacks melanin in albinism, problems related to the development and functions of the eyes arise, including the loss of pigmentation of the skin and hair, making a person highly susceptible to the ultraviolet rays and at increased risk of actinic damage and skin cancer.
The prevalence of albinism is estimated at 1:17000 to 1:20000 overall. There are multiple types of albinism and each is prevalent in different regions of the world. In Sub-Saharan Africa and America, the condition is highly prevalent.
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Types Of Albinism
There are two prominent types of albinism. The most common form of albinism is oculocutaneous albinism (OCA). It mainly affects the skin and the eyes. To date, there are seven types of OCA identified (OCA1 to OCA7). Another prominent type of albinism includes ocular albinism (OA), followed by Hermansky-Pudlak syndrome (HPS) and Chediak-Higashi syndrome (CHS)[1].
| Types | Definition |
| OCA1 | It is a defect in the TYR gene product tyrosinase. Loss of this gene causes an inability to synthesize melanin.
It is prevalent in America and China. |
| OCA2 | It is a defect in the OCA2 gene product, causing reduced production of P protein.
It is prevalent in African Americans. |
| OCA3 | It is a defect in the TYRP1 gene product that affects melanosomes that helps in the production and storage of melanin.
It is prevalent in Southern Africa. |
| OCA4 | It is a defect in the SLC45A2 gene product, which is responsible for normal pigmentation of the skin.
It is prevalent in Japan. |
| OCA5 | The defective gene is not yet identified.
It is very rare and noted in a few Pakistani families. |
| OCA6 | It is a defect in the SLC24A5 gene which is also responsible for the natural skin colour. It plays a key role in the evolution of light skin.
It is very rare and noted in a few Chinese and Indian families. |
| OCA7 | It is a defect in LRMDA that plays a role in melanocyte differentiation.
It is very rare and noted in the consanguineous Faroese family. |
| Ocular albinism (OA) | It is a defect in the GPR143 gene product that causes vision abnormalities. The condition is prevalent in males.
It is prevalent worldwide. |
| Hermansky-Pudlak syndrome (HPS) | It has two characteristics: albinism with visual problems and bleeding problems due to platelets dysfunction.
It is prevalent worldwide, mostly in Puerto Rico. |
| Chediak-Higashi syndrome (CHS) | It is characterised by oculocutaneous albinism with immune deficiency, leading to an increased risk of infection, bruise and bleeding.
It is very less with less than 500 cases in 20 years. |
Causes Of Albinism
According to a study, albinism was one of the first genetic diseases noted in human beings, but it was until recently when the molecular mechanism behind the condition was identified.
Albinism is caused due to mutation in at least seven different genes. These genetic mutations result in a reduction in melanin pigment biosynthesis, causing various clinical features such as hypopigmentation of the skin, eyes and hair and reduced vision. [2] The type of gene mutation determines its types and clinical features.
How Is Albinism Inherited?
As aforementioned, albinism is a genetic disorder related to insufficient or no production of melanin. In OCA (all types) and OA, the albinism gene is passed as an autosomal recessive inheritance pattern, meaning a child with albinism gets two copies of the albinism-causing gene from each parent.
When both the parents have a copy of albinism gene, they are referred to as a carrier and do not usually show symptoms of the condition. However, when two individuals who are carriers have a child, there is a 25 per cent risk of the child getting albinism, 50 per cent becoming an unaffected carrier (like their parents) and 25 percent to not have the condition and not be a carrier. [3]
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Symptoms Of Albinism
Complications Of Albinism
Some of the complications of albinism include: