By Dr Ananya Mandal, MD
Melanin is a vital pigment producing compound responsible for determining the colour of skin and hair. A deficiency in melanin can lead to several disorders and diseases. For example, a complete absence of melanin causes a condition called albinism. Melanin deficiency has previously been associated with various genetic abnormalities and congenital defects.
Some of the diseases associated with melanin include:
Albinism - There are almost ten different types of oculocutaneous albinism, conditions that are inherited in an autosomal recessive manner. This means both parents need to have been carriers of one copy of the mutated gene with the offspring receiving two copies.
The most common form is oculocutaneous albinism type 2 which is particularly common among people of African ethnicity and describes a reduction or absence of melanin in the hair, skin and eyes. The incidence of this type of albinism is around 1 in 10,000 among African Americans and 1 in 36, 000 among White Americans.
In some African nations the incidence of this type of albinism may be as high as 1 in 2000.
Another common form of albinism is the yellow oculocutaneous albinism observed in German or Swiss individuals. These people have white hair and white skin at birth but may develop normal pigmentation as they reach infancy and childhood.
Melanin deficiency is also associated with deafness. For example, in the case of Waardenburg's syndrome which is most common among the Hopi people in North America, the loss of pigmentation and deafness occur together. The prevalence of the syndrome among Hopi Indians is around 1 in 200.
The neurodegenerative disorder Parkinson's disease is associated with a lack of neuromelanin in the brain areas the substantia nigra and locus coeruleus. This is thought to arise from a reduction in dopaminergic pigmented neurons which leads to reduced dopamine synthesis in the brain.
Nicotine has a high affinity for tissues that contain melanin and is a precursor for melanin synthesis. It has been suggested that this is related to why nicotine dependence seems to be higher and cessation rates lower in individuals with darker skin pigments.
Reviewed by Sally Robertson, BSc