Urticaria

etiology & pathogenesis acute & ch urticaria

- autoimmune dt production of Abs that cross-link the IgE receptor on mast cells - allergen (in foods, inhalants & injections) 1% - drugs 9% - contact (eg: animal saliva, latex) - physical (heat, cold, P, sun, water) - infection 40%(eg: viral hepatitis, infectious mononucleosis, HIV infection during seroconversion) - other conditions (eg: SLE, pregnancy, intestinal parasites, malignancy, emotional stress) - idiopathic 30%

VS angioedema

- deeper swelling (ANGIOEDEMA) => painful > itchy & w longer duration (48 hrs) & larger - wheals & angio-edema may coexist in same pt - hourseness of voice , abd pain , vomiting, diarrhea (more in MM, lip, upper eye lids)

urticarial vasculitis causes

- hepatitis B - SLE - idiopathic

investigations

- hx - long the individual lesion last (< 24 hours it is urticaria, > 24 hours it is urticarial vasculitis) -long the cond has been present if < 6wk (acute urticaria) if > 6 wks (ch urticaria ix - full blood count include eosinophil count for parasites - erythrocyte sedimentation rate (ESR), inc in vasculitis - urea & electrolytes, thyroid & liver function tests, for underlying causes - total IgE & sp IgE to possible allergens eg: foods such as shellfish & peanuts - antinuclears factors in ch urticaria or urticarial vasculitis - skin biopsy if suspect urt vascu physical urticariars can be conformed by the appropriate physical challenge frequently, no cause can be found for acute episodes, whereas in ch urticaria the autoimmune pathogenesis will account for the majority of cases

Idiopathic

- in most cases the underlying cause is unknown - there is evidence for an autoimmune etiology in some of the 'idiopathic' cases as certain individuals dev autoantibodies against the high-affinity IgE rec alpha subunit of the mast cell

px

- most cases of idiopathic urt last a few weeks to months before disappearing spontaneously - a small percentage of people go on to develop ch urt which can last for several months or years - the physical urticarias (es cholinergic urt) are more persistent, often lasting for years, & they are often resistant to therapy

clinical features SYMPTOMS

- the history is of cut. swellings or wheals dev acutely over a few minutes - lesions are intensely itchy & show no surface change or scaling - mild constitutional symptoms mb present

urticarial vasculitis

- this is a variant of urticaria & should be suspected if individual urticarial lesions last longer than 24 hours & leave bruising behind after resolution - there is often an ass arthralgia or myalgia & a small proportion may go on to dev a connective tissue disease - the dx is confirmed by skin biopsy . a full vasculitis screen should be carried out for an underlying cause - tx: . abtihistamines . oral dapsone (50-100 mg daily) . immunosuppressants (calchicine??)

tx

- treat the underlying causes - pt should avoid salicylates & opiates as they can degranulate mast cells - oral antihistamine (H1 blockers) the most useful in treating idiopathic cases - started w regular use of a non sesating antihistamine (cetirizine 10 mg daily or loratadine 10mg daily) - if failed, add a sedating antihistamine or H2 blocker - systemic corticosteroids in short course in energency cases (severe acute) - dietary manipulation for ch urt - angiooedema of mouth & throat may required urgent tx w intramuscular epinephrine (adrenaline) & intravenous steroids. - leukotrien antagonist

def

- urticaria (hives, 'nettle rash') is a common allergic skin condition @ by the acute dev of: . supf itchy WHEALS or swelling in the skin . 2ry to a transient inc in capillary permeability dt: leaky dermal vessels

SITES

-occur anywhere on the skin & last btw minutes & hours b4 resolving spontaneously - severe urticaria w subcut involvement can present as soft tissue swelling (angio-oedema) es around the eyes, the lips & the hands

immunologic (allergic) causes

1. autoimmune : hashimoto thyroiditis dt production of Abs that cross-link the IgE receptor on mast crlls 2. ingested substances - food: strawberries, food colouring like food additives, eggs, seafood. - drugs : aspirin (NSAIDs), penicillin allergy 3. inhaled substances - dust, pollens, perfumes 4. injected substances - sera: antititanic serum - vaccines, insect bite & drugs 5. infections - bacterial (septic focus), fungal & parasites, viral (viral hepatitis), infection mononucleosis& HIV infection during seroconversion pathogenesis - the final event in pathog involves degranulation of cutaneous mast cells, which releases a number of inflm mediators (including histamine) that in turn make the dermal capillaries leaky 1. type I hypersensitivity (IgE mediated) m/c 2. type II hypersensitivity (cytotoxic reaction) Abs mediated eg: transfusion reaction 3. type III hypersensitivity (toxic complex s) eg: serum sickness (injection of large amount of foreign serum or drugs as penicillin) 4. type IV hypersensitivity (delayed or cell mediated) eg: intracellular infections

non immunogenic (non-allergic) causes:

1. physical agents - cold (cold urticaria) - stress or heat (cholinergic urticaria) - sunlight (solar urticaria) - P (P can cause two types of urticaria): . more supf P can cause dermographism, which is relatively common. this presents as urticated weals occuring a few minutes after application of light P . deep P (delayed P urticaria) is rare & occurs as deep swellings some hours after P is removed (eg: on the soles of the feet or under a tight belt) - water (aquagenic urticaria) - or chemicals such as latex (contact urticaria) 2. Psychosomatic factors 3. Direct mast cell degradation mediators 4. Food w high level of histamine eg: shell fish 5. Trauma PATHOGENESIS 1) direct release of histamine 2) blocking of PGs pathway f arachidonic acid

Differential Diagnoses

Atopic Dermatitis Contact Dermatitis, Allergic Drug Eruptions Erythema Multiforme Henoch-Schonlein Purpura (Anaphylactoid Purpura) Mastocytosis Pityriasis Rosea Scabies Urticarial Vasculitis

Laboratory Studies

For acute urticaria, laboratory studies generally are not indicated. The patient's history and physical examination should direct any diagnostic studies. For chronic or recurrent urticaria, basic laboratory studies should include a CBC, erythrocyte sedimentation rate, TSH, and an ANA looking for possible causes of the urticaria.

Mortality/Morbidity

Pruritus (itching) and rash are the primary manifestations of urticaria. Acute urticaria is usually self-limited and commonly resolves within 24 hours but may last up to 6 weeks. Chronic urticaria lasts more than 6 weeks. Neither acute nor chronic urticaria results in long-term consequences other than anxiety and depression.

Causes

The cause of acute generalized urticaria often is undetermined. Known causes include the following: Infections (eg, pharyngitis, GI infections, genitourinary infections, respiratory infections, fungal infections, malaria, amebiasis, hepatitis, mononucleosis, coxsackievirus, mycoplasmal infections, infestations, HIV, parasitic infections. Foods (particularly shellfish, fish, eggs, cheese, chocolate, nuts, berries, tomatoes)) Drugs (eg, penicillins, sulfonamides, salicylates, NSAIDs, codeine, antihistamines)) Environmental factors eg, pollens, chemicals, plants, dust, mold. Exposure to latex Exposure to undue skin pressure, cold, or heat Emotional stress Exercise Pregnancy, pruritic urticarial papules and plaques of pregnancy Chronic urticaria can be related to all of the above as well as to the following: Autoimmune disorders (SLE, rheumatoid arthritis, polymyositis, thyroid autoimmunity, and other connective tissue diseases); probably up to 50% of chronic urticaria is autoimmune Cholinergic urticaria induced by emotional stress, heat, or exercise. Chronic medical illness, such as hyperthyroidism, amyloidosis, polycythemia vera, malignant neoplasms, lupus, lymphoma. The etiology of chronic urticaria is undetermined in at least 80-90% of patients. Recurrent urticaria can be related to the following: Sun exposure -solar urticaria, occurring only on skin exposed to the sun Exercise (cholinergic urticaria( Emotional or physical stress Water (aquagenic urticaria)

Treatment:

The management of urticaria is straightforward and typically is not altered by underlying etiology. The mainstay is avoidance of further exposure to the antigen. Antihistamines, primarily the older sedating antihistamines that block the H1 receptors, are the first line of therapy for urticaria. H1-blocking antihistamines are effective in relieving the pruritus and rash of acute urticaria in most cases. Newer H1-blocking minimally sedating antihistamines are now available. These are used primarily in the management of chronic urticaria rather than acute urticaria. H2 antihistamines, have a role when used in combination with H1 antihistamines in urticaria. H1 and H2 antihistamines are thought to have a synergistic effect and often result in a more rapid and complete resolution of urticaria than H1 antihistamines alone. Antidepressant and an antihistamine that blocks both H1 and H2 receptors may be effective in refractory cases of urticaria. Glucocorticoids stabilize mast cell membranes and inhibit further histamine release. They also reduce the inflammatory effect of histamine and other mediators.

Clinical Picture Clinical Picture

Urticaria is characterized by blanching, raised, palpable wheals, which can be linear, annular (circular), or arcuate (serpiginous). These lesions occur on any skin area and are usually transient and migratory. These lesions are often separated by normal skin, but may coalesce rapidly to form large areas of erythematous, raised lesions that blanch with pressure.

Pathophysiology

Urticaria results from the release of histamine, bradykinin, leukotriene C4, prostaglandin D2, and other vasoactive substances from mast cells and basophils in the dermis. These substances cause extravasation of fluid into the dermis, leading to the urticarial lesion. The intense pruritus of urticaria is a result of histamine released into the dermis. Histamine is the ligand for 2 membrane-bound receptors, the H1 and H2 receptors, which are present on many cell types. The activation of the H1 histamine receptors on endothelial and smooth muscle cells leads to increased capillary permeability. The activation of the H2 histamine receptors leads to arteriolar and venule vasodilation.

def CIKGU

Urticaria, commonly referred to as hives, It appears as raised, well-circumscribed areas of erythema and edema involving the dermis and epidermis that are very pruritic. Urticaria may be acute (lasting less than 6 wk) or chronic (lasting more than 6 wk).

acute

last less than 6 weeks

ch

persist beyond 6 wks

MORPHOLOGY

the initial lesion is: URTICARIAL WHEAL - circumscribed area of dermal edema - slightly raised (plaque) & w variable sizes - mb confluent into large plaques w irregular borders - rounded or oval shape - it may undergo central healing ie: annular lesion - lesions are normally erythematous but if very acutely swollen, they may appear flesh-coloured or whitish & people often mistake them for blister - last for few hours (<24hours) ie: evasnescent