Psoriasis - Causes

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PSORs. Researchers have now identified four key genes (named PSOR 1 - 4) that are involved with psoriasis. Of particular interest are the genes located in regions on specific chromosomes that are linked to HLA and tumor necrosis factor, another immune component strongly associated with psoriasis.

Environmental and Other Triggers

Outside factors, including weather, stress, injury, and infection, while not direct causes, are often important in triggering the disease process leading to the start and worsening of psoriasis.

Weather. Weather is a strong factor in psoriasis:

• Cold, dry weather is a common trigger of psoriasis flare-ups.
• Hot, damp, sunny weather helps relieve the problem in most patients.
• To confuse matters, some people have photosensitive psoriasis, which actually improves in winter and worsens in summer when skin is exposed to sunlight.

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Stress and Strong Emotions. Stress, unexpressed anger, and emotional disorders, including depression and anxiety, are strongly associated with psoriasis flare-ups. In one study, nearly 40% of patients remembered a specific stressful event that occurred within a month of a psoriasis flare. A 2001 study suggested that stress can trigger specific immune factors associated with psoriasis flares. Some evidence indicated that people with psoriasis may respond to stress differently from those without the skin disease. In one study, psoriasis patients had fewer aggressive verbal responses than others did when confronted with hostile situations.

Infection. Infections caused by viruses or bacteria can trigger some cases of psoriasis. Some examples include the following:

• Streptococcal infections in the upper respiratory tract, such as tonsillitis, sinusitis, and so-called "strep" throat, are known to trigger guttate psoriasis in children and young adults. The infections may also worsen ordinary plaque psoriasis.
• The human immunodeficiency virus (HIV) is also associated with psoriasis.
• An uncommon form of human papillomaviruses (HPV) called EV-HPV has been associated with psoriasis. Although EV-HPV is probably not a direct cause, it may play an indirect role in the continuation of psoriasis. This HPV form is not the virus associated with cervical cancer and genital warts.
• Helicobacter pylori (H. pylori) infection, a major cause of peptic ulcers, has been proposed as a possible cause of psoriasis. Research in 2001 indicated that this is highly unlikely, at least in children.