Urticaria Disease

DESCRIPTION

Itchy rash. Single or multiple superficial raised pale macules with red halo. Subside rapidly; no scars or change in pigmentation. May be recurrent.

Acute urticaria
- Response to many stimuli
- IgE-mediated histamine release from mast cells
- Sometimes idiosyncratic response to drug exposure
- Subsides over several hours
Chronic urticaria: Persists > 6 weeks (30% of cases). Not mediated by IgE. Multiple types:
- Cold urticaria - from cooling, rewarming. Can be fatal (cold immersion with massive histamine release). Also a familial form with fever, chills, arthralgia, myalgia, headache, lymphocytosis.
- Cholinergic urticaria - heat urticaria. Small (5-10 mm) wheals on upper trunk from overheating, hot shower
- Exercise-induced urticaria - from extreme exercise; presents as cholinergic urticaria, angioedema, wheezing, hypotension. Often associated with eating food to which patient is allergic.
- Dermatographism - linear wheal and flare resulting from scratching the skin
- Solar urticaria - result of exposure to sunlight. Several types, by wavelength of light which induces reaction. Majority react to ultraviolet. Onset in minutes; subsides in 1-2 hours.
- Delayed pressure urticaria - occurs 4-6 hours after pressure to skin (elastic, shoes, etc.)
- Aquagenic urticaria - rare. Small wheals after contact with water at any temperature.
Idiopathic urticaria
- Acute or chronic
System(s) affected: Skin/Exocrine
Genetics: No consistent genetic pattern known
Incidence/Prevalence in USA: 1 in 1000. Affects 15-20% of population at some time during life.
Predominant age: All ages. Acute form mainly in children, young adults.
Predominant sex: Male = Female (chronic forms more often in older women)

SIGNS AND SYMPTOMS

Seen alone or with angioedema
May occur with generalized anaphylactic reaction, potentially fatal
Single or multiple raised, blanched, central wheals surrounded by red flare
Intensely pruritic
May occur anywhere on body
Variably sized, 1-2 mm to 15-20 cm or larger; sometimes confluent
Rapid onset, resolves spontaneously in less than 48 hours

CAUSES

Allergic or non-allergic; massive histamine release from mast cells in superficial dermis
Drug reaction (any drug) either from allergy or idiosyncrasy
Aspirin, NSAID's seem to trigger by inhibiting cyclo-oxygenase, without IgE
Food or food additive allergy
Allergy to peanuts and/or tree nuts: a leading cause of severe (sometimes fatal) food-induced allergic reactions. Affects 1% of the general population. Other foods that cause hives: chocolate, fish, tomatoes, eggs, fresh berries, milk. Also food additives and preservatives.
Inhalant, contact, or ingestant allergy
Transfusion reaction
Insect bite, sting
Infection - viral upper respiratory infections (esp. in children) and infectious mononucleosis, viral hepatitis; bacterial (strep throat, sinusitis, dental abscess, otitis); vaginitis; fungal (tineas); helminthic; protozoan. Helicobacter pylori has been increasingly associated with, and its eradication may stop, chronic urticaria.
Collagen vascular disease: cutaneous vasculitis, serum sickness, lupus
Thyroid autoimmunity: often associated; administering thyroid hormone may alleviate chronic urticaria in hypothyroid patients with autoantibodies
Physical trauma: heat, cold, sunlight, etc.
Emotional stress: reported; little supporting evidence
Histamine-releasing autoantibodies: identified in some cases of chronic idiopathic urticaria

RISK FACTORS

Listed with Causes

LABORATORY

More likely to discover the cause of acute than of chronic urticaria. Routine lab screening not helpful in diagnosing chronic urticaria.
Cause found in only 10-25% of chronic cases
Food and drug reactions - elimination diets, challenges with suspected agents
Inhalant allergens - skin tests, radioallergosorbent (RAST)
Idiopathic for > 6 weeks - CBC, skin biopsy, ESR, urinalysis, ANA
50% of patients with chronic urticaria have a cutaneous autoimmune disorder mediated by autoantibodies to the IgE receptor on mast cells.

Drugs that may alter lab results: Antihistamines, H2-blockers, tricyclic antidepressants
Disorders that may alter lab results: N/A

PATHOLOGICAL FINDINGS

Edema, vasculitis and/or perivasculitis involving only superficial dermis

SPECIAL TESTS

Cold urticaria - ice cube test (place ice cube on skin 5 minutes, observe 10-15 minutes)
Cholinergic or exercise-induced - exercise challenge; methacholine skin test (local reaction to 0.01 mg in 0.05 ml saline intradermally, 50% false negatives)
Dermatographism - scratch skin with piece of tongue blade, observe
Solar - expose to defined wavelengths of light; must rule out erythropoietic protoporphyria
Delayed pressure - apply 5-10 pound sandbag for 3 hours, observe
Aquagenic - apply tap water at different temperatures
Vibratory - apply vibration 4-5 minutes with a lab mixing device, observe
Infection - pharyngeal culture, antistreptolysin (ASO) titer, rapid plasma reagin (RPR), parasitology, liver function tests, mononucleosis test
Autoimmune - antinuclear antibody (ANA), rheumatoid arthritis (RA), complement, cryoglobulins, serum protein electrophoresis

IMAGING

N/A

DIAGNOSTIC PROCEDURES

Skin biopsy (correlates poorly with clinical picture)

APPROPRIATE HEALTH CARE

Don't work up acute cases (results usually inconclusive)

GENERAL MEASURES

Cool moist compresses help to control itching

SURGICAL MEASURES

N/A

ACTIVITY

As desired. Avoid overheating.

DIET

As desired. Avoid foods implicated as possible etiologic agents.

PATIENT EDUCATION

Avoidance if etiology is apparent. Antihistamines if accidentally re-exposed.

PREVENTION/AVOIDANCE

If etiology identified, avoidance is best solution

POSSIBLE COMPLICATIONS

Severe systemic allergic reaction (bronchospasm, anaphylaxis)

EXPECTED COURSE AND PROGNOSIS

70% better in < 72 hours. 30% chronic. 20% have attacks for > 20 years. Becomes chronic in 75% of patients with both urticaria and angioedema.

ASSOCIATED CONDITIONS

Angioedema, anaphylaxis

AGE-RELATED FACTORS

Pediatric: Acute isolated incidents are more frequent, chronic urticaria is rare
Geriatric: Less likely to occur in this age group
Others: N/A

PREGNANCY

Chronic urticaria

OTHER NOTES

Same pathophysiology for urticaria and angioedema - localized anaphylaxis causes vasodilatation, vascular permeability of skin (urticaria) or subcutaneous tissue (angioedema)

ABBREVIATIONS

N/A

Clinical Investigations

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