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Urticaria Dr.Amirhossein Siadat Associated Professor Isfahan University of Medical Sciences. DEFINITION.
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Urticaria Dr.Amirhossein Siadat Associated Professor Isfahan University of Medical Sciences
DEFINITION • Urticaria is defined as a skin lesion consisting of a wheal-and-flare reaction in which Iocalized intracutaneous edema (wheal) is surrounded by an area of redness (erythema) that is typically pruritic.
Individual hives can last from as briefly as 30 minutes to as long as 36 hours. • They can be as small as a millimeter or 6 to 8 inches in diameter (giant urticaria). • They blanch with pressure as the dilated blood vessels are compressed, which also accounts for the central pallor of the wheal.
Angioedemas : deeper dermal ,subcutaneus and sub mucosal tissues. • They are usually painfull rather than itchy ,poorly defined and pale or normal in color
Angioedema • Swelling of lips, face, hands, feet, penis or scrotum • Facial swelling most prominent in periorbital area • May be accompanied by swelling of the tongue or pharynx
Urticaria is classified to acute and chronic with a time devision between 6w and 3m. • When urticaria is present daily or almost daily for less than 6w it is acute.
PREVALANCE: • POINT PREVALANCE=0.1% • Cumulative life time prevalance:0.05-23.6% in general population but a range of 1-5% is more realistic • 72% ordinary urticaria,20%physical and choloinergic,3.4%allergic(exept stings and injected drug),2.1% u.vasculitis,0.5% hereditary angioedema
Clinical features of acute or chronic urticaria: • Ithcing erythematous macules develop into weals consisting of pale to pink edematous raised areas of skin often with a surrounding flare • It occurs any where (scalp and palms),in any number and size, any shape even bulla.
Wheals are often very itchy especially at night and resolve in a few hour without any residue. • Patient always rub not scratch so excoriation is absent. • Sometimes they bruise like in thigh. • Wheals are more prominent at evening and premens
In 50% of of urticaria: there may be angioedema. • Angioedema color is like skin ,most frequently on the face but any other area such as ear ,genitalia,hand and feet • It may last for several days, • It is not always itchy and and may be painful
Urticaria may be proceeded with vomiting. • It may be associated with: • malaise • loss of concentration • feeling hot or cold • headache • vomiting • abdominal pain • diarrhoea • arthralgia • dizziness • scyncope • And even anaphylaxies
1) Central dusky purpuric area2) Elevated edematous pale ring3) Surrounding macular erythema
Histamine: the most important mediator of urticaria. Histamine is produced and stored in mast cells. There are several mechanisms for histamine release via mast cell surface receptors.
Phathophysiology: • Urticaria is due to a local increase in permeability of capillaries of venules. • It is due to activation of cutaneus mast cells that contain many mediators predominantly histamin.
Pathophysiology of Urticaria Immunologic factors Non-immunologic factors Types II and III complement activation Chemical histamine liberators eg. Opiates, polymyxin antibiotics, thiamine Alternative complement pathway action Physical agents, e.g. cold, heat, sunlight Anaphylatoxins (C3a, C5a) released mediators (particularly histamine) endogenous hormone Cholinergic vasodilating factors Small blood vessel vasodilation Type I IgE mediated genetic factors modulating factors URTICARIA
Food origin is important in the etiology of infantile urticaria. • Food allergyfor 62% of patients • drug etiology (22%) • physical urticaria (8%) • contact urticaria (8%). Infantile Urticaria
Antibiotics especially penicilin and cephalosporin are common causes. • Risk factors: • previous exposure • reaction to a drug or chemically related drug • intermittant and multiple drug therapy , • familial predisposition
