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P
soriasis is a chronic inflammatory disease of the skin
characterised by a relapsing and remitting course. It manifests as pink,
scaly, raised lesions on the elbows, knees, lower back and scalp along
with certain nail changes like pitting, discolouration, subungual
hyperkeratosis and onycholysis in about 25-50% of the cases. In 5-10% of patients,
the disease can be associated with joint involvement.
It is multifactorial in
aetiology, with genetic factors and environmental insults playing their
role. A positive family history is present in about one third of the patients;
when neither parents are affected the risk is about 7.5%, when one
parent is affected it is about 15% and when both parents affected, it is 50%.
Psoriasis is not contagious.
The following
factors may exacerbate the disease:
Psoriasis is not a
contagious disease
- Stress
- Trauma
- Infections
(Streptococcal upper respiratory tract infections)
- Medications (Lithium,
Antimalarials, Propranolol and other beta blockers,
NSAIDS, Terfenadine and steroid withdrawal)
- Winter season
Role of Diet: Diet has been
suggested to play a role in the aetiology and pathogenesis of
psoriasis. Diets with low carbohydrates and rich in vegetables and
omega 3 polyunsaturated fatty acids (fish such as meckerel,
salmons, sardines) improved psoriatic symptoms in some studies.
Animal studies indicate that fatty acids can modulate
pro-inflammatory cytokine production and actions. Omega 6
polyunsaturated fatty acids such as arachidonic acid (from meat,
refined vegetable oils) enhance interleukin 1 production and
tissue responsiveness to cytokines whereas omega 3 polyunsaturated
fatty acids such as eicosa pentanoic acid (EPA) and docosa
hexanoic acid (DHA) (from fish such as meckerel, salmons,
sardines) have the opposite effect. Arachidonic acid is converted
to prostaglandin (PG) E2
and leukotreine (LT) B4 which are proinflammatory whereas EPA and
DHA are converted into PGE3
and LT B5 which are anti inflammatory. Overproduction of
arachidonic acid derived eicosanoids have been implicated in many
inflammatory and autoimmune disorders including psoriasis. A
diet rich in vegetables and fish is beneficial because it is
associated with reduced arachidonic acid intake. Low calorie
diet helps in reducing the oxidative stress and thereby improves
psoriasis. Weight reduction in obese also helps in improvement of
psoriasis.
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