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Some scientists separate Psoriasis into 2 types:
- Type 1 Psoriasis - associated with HLA;
- Type 2 Psoriasis - not associated with HLA.
So What is HLA?
HLA is an acronym for Human Leukocyte Antigens.
Human Leukocyte Antigens are genetic markers located on the surfaces of all white cells (leukocytes) and on the surfaces of most other cells in a human body. These markers identify body cells as "self" and the foreign cells as... well... "foreign". HLA molecules prevent the immune system from attacking the "self" cells and help to recognize the unmarked "foreign" cells. When the immune system finds an unmarked foreign cell, it starts to attack it.
HLA molecules are inherited from ones parents and therefore the chance of having the same HLA type is the greatest between siblings. HLA markers are used to determine tissue compatibility when searching for a donor within ones family or from the volunteer donors in order to match donated organs or bone marrow with the transplant recipient.
HLA have 2 sets of cell surface molecules - HLA class I and HLA class II. The major groups are: HLA-A, HLA-B, HLA-C, HLA-DR and HLA-DQ. There are two A numbers, two B numbers, two C numbers, two DR numbers and two DQ numbers. Altogether there are more than a hundred different HLAs.
Some HLA markers are associated with the increased risk of developing different Types of Arthritis, Type 1 Diabetes etc.
HLA and Psoriasis
Type 1 Psoriasis
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Type 1 Psoriasis begins at a young age - usually in people between 14-25 years old.
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Type 1 Psoriasis is associated with the HLA system (the specific genetic HLA markers were revealed in 85.3% of the cases).
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Type 1 Psoriasis is believed to be caused by the breakdowns in the immune system transmitted genetically.
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About 65% of people with psoriasis have Type 1 Psoriasis.
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Type 1 Psoriasis predominantly affects the skin.
Type 2 Psoriasis
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Type 2 Psoriasis begins later - usually in people older than 40 years old.
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Type 2 Psoriasis is not associated with the HLA system. Family history of psoriasis in the case of Type 2 Psoriasis is also absent.
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Type 2 Psoriasis begins spontaneously.
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About 35% of people with psoriasis have Type 2 Psoriasis.
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Type 2 Psoriasis predominantly damages the nails and the joints.
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