Urticaria and erythema nodosum Notes

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NOTES NOTES URTICARIA & ERYTHEMA NODOSUM GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Vascular reaction of the skin triggered by allergic reaction, irritation, or infection ▪ Vasodilation, increased vascular permeability → fluid leaks into interstitium → swelling/edema ▪ Possible elicitation of hypersensitivity reaction (immune system involved) ▪ Can be acquired (e.g. medications), associated with underlying illness (e.g. malignancies, autoimmune disorders), or have genetic predisposition SIGNS & SYMPTOMS ▪ Range of dermatological manifestations: ▫ Erythema ▫ Swelling ▫ Urticaria, pruritus ▫ Raised or flat lesions DIAGNOSIS ▪ Physical examination ▫ Based on appearance ▪ Patch testing to confirm and determine the allergy ▪ Screening for autoimmune or neoplastic etiologies TREATMENT ▪ Identify/avoid triggers ▪ Address underlying cause ▪ Symptomatic management ERYTHEMA NODOSUM osms.it/erythema-nodosum PATHOLOGY & CAUSES ▪ Acute skin eruption due to inflammation in the subcutaneous adipose tissue ▫ Most common form of acute panniculitis ▪ Chronic or recurrent forms are rare but may occur ▪ Presumably caused by a delayed hypersensitivity type IV reaction to a variety of antigens CAUSES ▪ 30–50% unknown etiology ▪ Infections: Streptococcus spp., M. tuberculosis complex, M. leprae, M. pneumoniae, Yersinia spp., Histoplasma capsulatum, Coccidioides immitis ▪ Autoimmune disorders: inflammatory bowel disease, sarcoidosis, Behçet’s disease, medium-vessel vasculitis ▪ Medications: sulfonamides, oral contraceptives, amiodarone OSMOSIS.ORG 59
▪ Malignancies: hematological malignancies, carcinoid tumours, pancreatic cancer SIGNS & SYMPTOMS ▪ Pre-eruptive phase ▫ Fever, malaise, and arthralgia ▪ Eruptions of red, painful, poorly defined plaques and nodules, most commonly located on shins, knees, arms, thighs, and torso → skin lesions gradually get softer and smaller until they completely disappear over the course of about two weeks DIAGNOSTIC IMAGING Chest X-ray ▪ Additional evaluation to determine the underlying cause TREATMENT MEDICATIONS ▪ Potassium iodide, corticosteroids and colchicine can be used in severe refractory cases OTHER INTERVENTIONS ▪ Address underlying cause ▪ Symptomatic management ▫ Bedrest, leg elevation, compressive bandages, wet dressings, and nonsteroidal anti-inflammatory agents Figure 9.1 A single area of erythema nodosum. DIAGNOSIS ▪ Observation of typical skin lesions LAB RESULTS ▪ Biopsy in uncertain cases ▪ Additional evaluation to determine the underlying cause ▫ Complete blood count, erythrocyte sedimentation rate, antistreptolysin-O titer, throat culture, urinalysis, intradermal tuberculin test, venereal disease research laboratory (VDRL), and cultures, as appropriate 60 OSMOSIS.ORG Figure 9.2 Erythema nodosum affecting the shins; a common site for this disease.
Chapter 9 Urticaria & Erythema HEREDITARY ANGIOEDEMA (HAE) osms.it/hereditary-angioedema PATHOLOGY & CAUSES ▪ Small but important number of all cases of angioedema ▫ Increased vasodilation and vascular permeability → fluid leakage from deep blood vessels → angioedema ▫ Urticaria and pruritus are not present ▪ Attacks begin during childhood and become increasingly frequent and severe ▪ Frequency of attacks differs greatly, varying from weekly episodes to intervals longer than a year; discrepancies can occur among different individuals and at different times in the same individual CAUSES ▪ Inherited in an autosomal dominant manner involving mutation of genes associated with C1-inhibitor (C1INH) that inhibits the complement pathway and is associated with coagulation factor XII ▫ Results in unregulated levels of bradykinin and other vasoactive substances → inflammation, vasodilation, and cellular injury ▫ Attack triggers may include minor trauma, mood and temperature changes, but often no obvious inciting event can be established SIGNS & SYMPTOMS ▪ Recurrent attacks of angioedema ▪ Painless, nonpruritic, nonpitting swelling of extremities, genitalia, buttocks, eyelids, lips, tongue, larynx or gastrointestinal tract ▫ Gastrointestinal tract → nausea, vomiting, intense colicky abdominal pain, diarrhea, dehydration, and intense exhaustion → mimics a surgical emergency and unnecessary surgery could be performed ▫ Larynx → life-threatening airway obstruction → without treatment, death by asphyxia occurs in about 25% ▪ Tightness, tingling, or erythema marginatum corresponding to the affected area may precede the swelling ▪ Each episode usually resolves within 72 hours Figure 9.3 Angioedema of the lips. DIAGNOSIS DIAGNOSTIC IMAGING ▪ Imaging studies may be useful during attacks of gastrointestinal edema LAB RESULTS ▪ Complement testing to assess alterations in the system TREATMENT MEDICATIONS ▪ Management of attacks ▫ Intravenous C1-inhibitor concentrates, kallikrein inhibitors (ecallantide), bradykinin B2 receptor antagonists (icatibant) or, if those are unavailable, fresh-frozen plasma as an alternative OSMOSIS.ORG 61
▪ More than one episode in a month or high risk of developing laryngeal edema → longterm prevention ▫ Danazol (an androgen that increases levels of C4) ▫ C1-inhibitor concentrates OTHER INTERVENTIONS ▪ Avoid specific stimuli that have previously led to attacks ▪ Avoid medications associated with attacks ▫ ACE inhibitors; medications containing estrogen URTICARIA (HIVES) osms.it/urticaria PATHOLOGY & CAUSES ▪ Acute (< six weeks) or, rarely, chronic (> six weeks) skin eruption ▪ Acute form most common dermatologic disorder seen in emergency department ▫ Most often benign and self-limiting, though may rarely progress to lifethreatening angioedema or anaphylactic shock; strong tendency to recur ▪ Hypersensitivity reaction → mast cell degranulation and release of inflammatory mediators → increased vascular permeability → fluid leakage from superficial blood vessels → cutaneous lesion TYPES ▪ Acute urticaria ▫ Single lesions usually last less than 24 hours ▪ Chronic urticaria ▫ May last six weeks or more ▪ Precipitants include psychological and physical stress, cold or hot temperature, pressure or vibration ▪ Physical urticaria is urticaria is induced by an exogenous physical stimulus such as scratching or firm stroking of the skin ▫ The most common type of physical urticaria is called a dermatographism SIGNS & SYMPTOMS ▪ Wheals: skin eruption characterized by itchy, burning or stinging, red, raised plaques with well-defined erythematous margins and pale centers ▫ Individual lesions may coalesce ▫ New lesions may appear as others resolve ▪ Can occur anywhere, but common sites are areas exposed to pressure (e.g., trunk, distal extremities, ears) CAUSES ▪ Assessment for potential causes includes “5 Is” ▫ Infection (bacterial/viral/fungal/parasitic) ▫ Injection of a drug/insect venom ▫ Inhaled substances (pollen, mold, dust) ▫ Ingestion of foods, drugs, chemicals ▫ Internal disease process such as an autoimmune disorder ▪ Vasculitis urticaria associated with autoimmune and malignant diseases 62 OSMOSIS.ORG Figure 9.4 Urticaria of the forearm.
Chapter 9 Urticaria & Erythema DIAGNOSIS ▪ Typically based on appearance ▪ Patch testing to confirm and determine the allergy LAB RESULTS ▪ Complete blood count ▪ Erythrocyte sedimentation rate ▪ Thyroid-stimulating hormone (rule out thyroid disease) ▪ Autoimmune screening TREATMENT ▪ Avoid triggers ▪ Symptomatic management ▫ Antihistamines ▫ In severe cases, corticosteroids or leukotriene inhibitors ▫ Monoclonal antibodies and immunosuppressants may be used in refractory cases OSMOSIS.ORG 63

Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Urticaria and erythema nodosum essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Urticaria and erythema nodosum by visiting the associated Learn Page.