Albinism causes - Albinism disorder types and genetics

Home > White skin discoloration > Albinism facts > Albinism disorder causes, types and genetics

There are several types of albinism disorders and all types are caused by genetic defects rendering the body incapable of producing or distributing melanin pigment.

Most of these genetic defects are caused by recessive alleles. A person has to receive the defective genetic material from both the parents to get the albinism disorder. If the person receives the mutated gene from only one parent, he will be normal, but will be a genetic carrier. Normally carrier-parents have 25% chances for producing children with albinism disorder. There are currently 15 genetic locations in the chromosomes that have been associated with albinism.

Genetic defects affecting melanin pathway causes albinism disorders

The pigment melanin is formed in the melanocytes present in the skin, hair follicles and pigment cells of the eye. The production of melanin involves a series of enzymatic reactions converting the amino acid tyrosine into two types of melanin, namely black-brown eumelanin and red-blond pheomelanin. Genetic mutations affecting proteins and enzymes involved in melanin production pathway cause  non-production or reduced production of melanin. Tyrosinase enzyme has a major role in converting tyrosine to DOPA. DOPA is then converted to dopaquinone and then to eumelanin or pheomelanin. Tyrosinase-related protein 1 and tyrosinase-related protein 2 are also involved in formation of eumelanin. P protein (a melanosomal membrane protein) is involved in the transport of tyrosine for mealnin synthesis. Any genetic mutation affecting these enzymes and proteins can cause albinism disorder.

Genetics and causes of oculocutaneous albinism (OCA)

In oculocutaneous type of albinism disorder eyes (ocular), skin (cutaneous) and hair are involved. One of the four mutated genes causes this albinism disorder. Oculocutaneous albinism has four sub types OCA1, OCA2, OCA3 and OCA4 caused by mutated genes TYR, OCA2, TYRP1, and SLC45A2 respectively.
 
Oculocutaneous albinism type 1 (OCA1) is Tyrosinase-Related OCA and is caused by mutated TYR gene on the chromosome 11. There is a genetic defect in the tyrosinase enzyme which is responsible for the metabolism of amino acid tyrosine into Melanin pigment. Oculocutaneous albinism type 1 is transmitted by autosomal recessive inheritance. The characteristics of OCA1 type are deficient melanin synthesis in the skin, hair and eyes, nystagmus, reduced visual acuity and iris translucency.  At birth the affected children with this type of albinism disorder usually have white skin, white hair and blue eyes. Later on some of them may produce some pigment to have a slight tan and blond hair.

Oculocutaneous albinism 1A (OCA1A) is Tyrosinase-Negative OCA. The genetic defect in the tyrosinase enzyme makes it inactive and melanin is not produced. Individuals having oculocutaneous albinism type 1A have white hair and skin. The skin does not tan and the iris remain translucent and does not darken with age. It causes reduced visual acuity.

Oculocutaneous albinism 1B (OCA1B) is Yellow OCA. The genetic defect in the tyrosinase enzyme makes it minimally active and a small amount of melanin pigment is produced. Individuals with oculocutaneous albinism type 1B have white or light yellow hair and white skin at birth. The hair may darken with age. The skin may develop light pigment and tan. The blue iris at birth may turn hazel/green/brown with age. Individuals having OCA1B type disorder have better visual acuity when compared to OCA1A type individuals.

Temperature-sensitive albinism is a sub-type of oculocutaneous albinism type 1B. In this genetic disorder there is mutation in tyrosinase gene and causes temperature-sensitive tyrosinase enzyme to be produced. Temperature-sensitive tyrosinase enzyme has reduced activity than normal tyrosinase enzyme at normal temperatures (37*C). Its activity improves with lower temperatures. Parts of the body with normal temperature like scalp hair and axillary hair have minimal pigment while cooler areas of the body like arms and legs are greatly pigmented.

Oculocutaneous albinism type 2 (OCA2) is caused by OCA2 gene mutation on the chromosome 15. In OCA TYpe 2 disorder there is a genetic defect in P protein which helps in the function of tyrosinase enzyme. Oculocutaneous albinism type 2 disorder is transmitted by autosomal recessive inheritance. OCA2 is characterized by reduced pigmentation of the skin, hair and iris. This type of disorder causes ocular defects, including nystagmus, iris translucency and reduced visual acuity. Skin pigmentation may vary from minimal to near-normal. Newborns have pigmented hair ranging from very light yellow to brown. There is a variant of OCA2 disorder identified in Africans and African Americans which causes light brown skin and hair.

Oculocutaneous albinism type 3 (OCA3) is caused by mutation of TyRP1 gene on the chromosome 9. OCA type 3 disorder is transmitted by autosomal recessive inheritance. This is a very rare type of disorder caused by genetic defect in TYRP1, a protein related to tyrosinase enzyme. There is substantial pigmentation in people with OCA3.

Oculocutaneous albinism type 4 (OCA4) is caused by mutated SLC45A2 gene on the chromosome 5. This disorder is caused by defect in the SLC45A2 protein that helps the function of tyrosinase enzyme. OCA4 is transmitted by autosomal recessive inheritance. OCA4 is characterized by reduced pigmentation of the skin, hair and iris. Ocular defects include nystagmus, iris translucency and reduced visual acuity. Skin pigmentation may vary from minimal to near-normal. Newborns have some pigmentation in hair ranging from silvery white to light yellow. OCA4 is rarer except in people of Japanese origin.

Genetic causes of ocular albinism

Ocular albinism (OA1) is caused by mutation of GPR143 gene on X chromosome. It is passed on to sons by carrier-mother (50% chances). For the daughters to inherit OA1, father must have OA1 and mother should be either a OA1 (100% chances) or carrier (50% chances). Ocular albinism disorder affects only eyes and causes minimal pigment in them. Reduced visual acuity, nystagmus, and difficulty controlling eye movements are caused in persons with ocular albinism.

Hermansky-Pudlak Syndrome (HPS)
HPS is a rare type of albinism and is autosomal recessive. This disorder is more common in Puerto Rico.
HPS can be caused by mutations in several genes: HPS1, HPS3, HPS4, HPS5, HPS6 and HPS7. HPS shows all the characteristics of oculocutaneous albinism. HPS also has bleeding problems due to a platelet abnormality in lacking dense bodies and storage of an abnormal fat-protein compound. This disorder may also involve lung and bowl malfunctions.

Chediak-Higashi Syndrome (CHS)
CHS is a rare autosomal recessive disorder caused by the mutation of LYST gene. Individuals with CHS show characteristics of oculocutaneous albinism, having light skin and silvery hair. They are also afflicted by solar sensitivity, photophobia, frequent infections and neuropathy. A defect in the granules present in skin pigment cells and white blood cells causes this type of albinism associated with immunodeficiency. Albinism disorder is typically partial, and some individuals may also have peripheral neuropathy.

Griscelli Syndrome
Griscelli syndrome is a rare autosomal recessive disorder, characterized by albinism with immunodeficiency and neurological problems. It usually causes death in early childhood.

To sum up there are various genetic causes giving rise to various types of albinism disorders requiring further research and social efforts to alleviate the problems of the affected people.

Topic of interest:
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References:
Richard A King, MD, PhD, FACMG and William S Oetting, PhD., Oculocutaneous Albinism Type 2, University of Minnesota Health Center, Minneapolis, PMID: 20301410.

Causes of vitiligo skin disease - loss of skin pigment - white patches

White spots on skin, lips, fingernails, teeth, tonsils and genitalia > Vitiligo white skin patches > Causes > Signs > Diagnosis - Treatment and cure - Recent research

Vitiligo causes loss of skin pigment giving rise to white skin patches.
Vitiligo disease causes depigmentation of the skin in patches.

There are a number of possible causes for the onset of the disease. This disorder of white patches is believed to be primarily brought about by an autoimmune disease.

Autoimmunity causes vitiligo disorder

The most strong and accepted view about the causes of loss of pigmentation is autoimmunity.
In an autoimmune disease an individual's immune system reacts and destroys his own organs and body tissues.

In vitiligo disorder, the immune system produces certain proteins known as cytokines (immunomodulating agents) which target and alter the pigment producing melanocytes and leads to their gradual death resulting in white skin patches.
There is another view that some autoimmune factor causes the self destruction of melanocytes and loss of pigment.

Persons already affected by other autoimmune disorders like psoriasis, rheumatoid arthritis and thyroid disease have the greater risk of loss of pigmentation.
The autoimmune disease of the adrenal glands (Addison's disease) has been associated with the occurrence of this disorder.
Thyroid disorder causes the disease with white patches having no pigment.
Inflammatory and autoimmune diseases of thyroid glands lead to their over expression or under expression.

Persons with this thyroid impairment have been found prone to loss of pigment.

Hereditary factors in loss of pigment

Strong evidence is pointing towards inheritance in persons whose close blood relatives already have this disorder.
There is a great possibility of children of the vitiligo affected parents developing this white patches.
It has been found that 30% of the persons affected by this disorder have at least one family member affected by the disorder of loss of skin pigment.
Individuals with vitiligo pigment disorder seem to inherit a batch of multiple genes which make them susceptible to loss of pigmentation.
Vitiligo affected hand Physiological conditions and stress like sun burn and skin injury sometimes seem to be one of the causes for white patches.
Psychological stress triggers and leads to loss of pigment.
Environmental factors can also be the reason for white vitiligo patches.

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Vitiligo - skin disease - depigmentation - white skin patches

White spots on skin, lips, fingernails, teeth, tonsils and genitalia > Vitiligo white skin patches > Causes > Signs > Diagnosis - Treatment and cure > Recent research

Vitiligo is a skin disorder or disease in which there is loss of skin pigment resulting in white depigmentation patches.

What is vitiligo (leucoderma or leukoderma)?

Our skin color is due to the melanin pigment present in it. The melanin pigment is produced by specialised cells in the epidermis called melanocytes. The melanin pigment is formed into bundles called melanosomes and deposited in the epidermis.
Due to some physiological conditions there is stoppage of pigment production or death and loss of the pigment producing cells in patches and white areas of depigmentation occur.
This condition of loss of pigmentation is called vitiligo (leucoderma or leukoderma).

Causes for vitiligo disorder

Though the basic cause of this disease is the depigmentation of the skin there are divergent views, theories and research results pointing to many possible factors like physiological conditions, hereditary disorders, genetic disorders, environmental factors, thyroid disorders, psychological stress and autoimmune diseases.
For more details about the causes read the page ' causes for vitiligo disorders'.

Who can be affected by this condition of depigmentation?

Worldwide it is estimated that this condition of loss of skin pigment is affecting 1-2% of the population.
This disease affects all races and both genders and appears prominent in dark skinned people.
Persons with autoimmune disease and thyroid disorder are prone to get vitiligo disorder.
The chances for the immediate relatives of an affected person to get this disorder are greater.

Patterns and types of vitiligo disease

Three types of this loss of skin pigmentation, namely focal, segmental and nonsegmental vitiligo are observed.
In the focal form of the disorder, the white patches are restricted to one or a few areas.
In non-segmented form the white patches appear on both sides and somewhat show symmetry.
These white patches of skin grow over a period of time to spread all over the body.
If the depigmentation is total or only a few pigment patches remain, the condition is called as vitiligo universalis.
Segmental vitiligo disease affects younger individuals. The disorder affects some parts of the body and may not appear in symmetry.

Diagnosis of white skin patches

Vitiligo disease appear as white skin patches around orifices of the body like mouth, nostrils, eyes etc. They also appear on the end of the limbs like fingers and toes.
These white patches are irregular in shape and keep growing in most of the affected persons. For more detail about diagnosis of the disorder read 'Diagnosis of vitiligo disease'.

Therapy and treatment for vitiligo skin disease

There is a difference between the approach towards this disorder between the western medicine and the oriental medicine.
In oriental medicine the claim is that it is addressing the underlying cause of the disease.
There are number of ways to alter the appearance in the vitiligo skin disease affected.
The white vitiligo disease patches can be hidden by application of camouflage creams and skin dyes.
Further treatment methods for the disease like topical application, oral medicine, phototherapy, surgical grafts, repigmentation and treatment with melanocyte cultures are possible.
For detail information on treatment of this disorder read the page "Therapy and treatment of vitiligo disease".

Psychological and aesthetic aspects of the disorder of loss of skin pigment

Though this disease has no harmful effects on the body, it devastates the mental health of the affected person leading him to mood and depression disorders.
The loss of aesthetic appearance and being stigmatised for the condition ruins the self-esteem and emotional health of the person affected by the disorder.
Those affected by this disease are tormented sub-consciously about others reactions, feel ashamed, embarrassed and dejected and may become introverts.

Support groups for the vitiligo disease affected

Considering the psychological impact of this disorder all over the world, a number of organisations have come up to help out the affected by educating them and providing them advice, counsel and course of treatment for the disease.
These efforts are to save the affected from becoming a burden on the society just because of this harmless skin condition.

Research on pigmentation, depigmentation and repigmentation of this skin disorder

Wide spread research is going on to tackle this disorder. Methods for repigmentation of these white skin patches are already known and further research is going on .
If the vitiligo disorder has affected more than 50% area, a process for depigmentation of the rest of the skin pigment is now known. Further research is being carried out in this aspect of tackling vitiligo disease.

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Tactile defensiveness - Tactile sensitivity - Sensory processing disorder

Home › Skin senses › Skin sensitive to touch › Tactile defensiveness - tactile sensitivity

Tactile defensiveness (tactile sensitivity) is a sensory processing disorder in which the affected person experiences hyperarousal and exaggerated sensitivity to touch resulting in great distress and discomfort.

Tactile defensiveness is a sensory disorder of the midbrain region wherein the filtering of the incoming stimuli is affected resulting in exaggerated perception of the touch stimuli.

About 75% of the boys with 'fragile X syndrome' and some girls with full X mutation are found to suffer from tactile sensitivity.

The daily life of the tactile defensiveness affected person becomes very miserable. The daily routines like changing dress, brushing teeth and taking bath become arduous tasks. Some of the reactions of the affected children are as follows.

• The tactile defensiveness affected child may be greatly distressed by gentle touch.He may hate being touched on the face.
• He may hate coarse clothes. The very feel of the dress on him may distress him.
• The tactile defensiveness affected person will dislike anything around the neck like tie, jewellery and shirt collar.
• The person with tactile sensory processing disorder may dislike walking bare-footed and the feel of grass, soil or carpet may annoy him.
• The tactile defensiveness affected may dislike touching anything slimy and sticky.
• The sensory processing disorder affected child may dislike brushing teeth and a visit to a dentist becomes an ordeal.
• The tactile defensiveness affected person may lash out if somebody bumps on to him accidentally or touches or hugs him from behind.
• Group games are disliked by him and the possibility of touched by others will be avoided by him (even holding hands of partner).
• He may suffer from bed-wetting, confusion and motor muscle coordination difficulties.
• Strong preferences of foods may be there and the affected may dislike texture of certain food items.
• The tactile defensiveness affected person may dislike vibrating toys.
• He may dislike wind blowing on his body and may so sensitivity to change of temperatures.

The real remedy lies with parents and people in close contact with sensitivity affected child understanding the real problem of tactile defensiveness.

Just imagine a spider crawling on tour arm or your arm being rubbed with a sand paper and your reactions to it.

Similarly a person afflicted with tactile defensiveness has extreme sensitivity and reacts even to normal stimuli.

The sensitivity can be alleviated to great extent by Wilbarger Brushing Protocol, wherein the child's skin is brushed daily with soft surgical brush using a firm pressure.

Repetition of this process over an extent of time will reduce the hyper sensitivity of the skin of the affected person.

The joints of the arms and legs are pressed for sometime regularly. A finger is swiped inside the mouth to desensitize the mouth and reduce sensitivity.

In these treatments there is slow but sure reduction in the tactile defensiveness of the affected child. Soft and seamless clothing for the sensitivity affected children helps a lot.

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