Urticaria (Figure 3.21A, B) - Discrete pink areas of swelling involving either superficial skin or mucosa with associated pruritus; lesions last < 24 h, ± associated angioedema
- Acute urticaria < 6 weeks, chronic > 6 weeks
- Urticaria due to cross-linking of two or more high affinity IgE receptors (FcєRI) with subsequent release of mast cell storage granules:
- Newly formed mediators: prostaglandin D2, leukotriene C4/D4/E4, platelet-activating factor (PAF)
- Preformed: histamine, heparin, tryptase, chymase
- Causes: idiopathic, immunologic, non-immunologic
- Immunologic
- IgE-mediated type I hypersensitivity (allergic)
- Immune complex deposition (serum sickness)
- Complement-dependent
- Autoantibodies: anti-IgE or anti-FcєRI antibodies (most often seen in chronic urticaria)
- Non-immunologic (direct/indirect degranulation)
- Drugs (opiates, radiocontrast dye, polymyxin B, aspirin, NSAID), contact-induced (i.e. nettle stings), certain foods
- Histology: perivascular infiltrate of scant eosinophils and lymphocytes (sometimes neutrophils), ± eosinophils splayed between collagen bundles, ± dermal edema
- Treatment: remove trigger; antihistamine (H1), ± short course of oral corticosteroid; if chronic urticaria consider lab work (CBC, ESR, ANA, anti-IgE/FcєRI antibodies, anti-thyroid antibodies, stool ova/parasite)
| | | | | | | Type of Urticaria | | Description | | | Dermographism | | Urticarial lesions resulting from light scratching | | | Delayed pressure urticaria | | Deep swelling with overlying erythema at sites of sustained pressure occurring with a delay of up to 12 h | | | Cholinergic urticaria | | Small erythematous papules appearing within 15 min of sweat-inducing stimulus (i.e. physical exercise) | | | Solar urticaria | | Occurs typically within minutes of exposure to sun (UV or visible light), lasts for <1 h, may have accompanying headache and syncope | | | Aquagenic urticaria | | Eruption after contact with water, typically lasts for <1 h | | | Cold urticaria | | Urticaria in cold-exposed areas (often seen when skin rewarmed) | | | Contact urticaria | | Urticaria at site of contact (i.e., nettle stings, latex) |
| | | | | |
|
Angioedema (Without Urticaria) (Figure 3.22A, B) - Deep form of urticaria with localized non-pitting edema
- Presents with episodes of painful deep swelling of subcutaneous tissue (especially periorbital/lips), GI tract (abdominal pain) and upper respiratory tract (laryngeal edema), lasts > 24 h (usually few days)
- Etiology: idiopathic, drug-related (NSAID, ACEI) or abnormality of C1 inhibitor (C1-INH)
| | | | | | ACEI: results in unregulated generation of bradykinin | | | | | |
|
- C1-INH: serine protease inhibitor, prevents spontaneous activation of complement system
- Hereditary angioedema (HAE)
- Autosomal dominant
- C1-INH deficiency
- Type 1: ↓ C1-INH level
- Type 2: normal/↑ C1-INH level, but dysfunctional
- Presents in 1st or 2nd decade
- Labs: ↓ C4, ↓ C1-INH (level and/or function); C1q normal
- Histology: perivascular lymphocytic infiltrate and dermal edema
- Treatment: C1-INH concentrate during acute attack (of note, antihistamine, epinephrine, corticosteroid → not typically effective); fresh frozen plasma (FFP) before surgery; prophylactic treatment with attenuated androgens like danazol and stanazolol
- Acquired C1 inhibitor deficiency (AAE)
- Usually seen after fourth decade, no family history; due to destruction of C1-INH function through either immune complexes or autoantibodies
- Presentation similar to HAE
- Type 1: associated with lymphoproliferative disorders (i.e. B cell lymphoma, multiple myeloma, non-Hodgkin’s lymphoma) with significant amounts of immune complexes consuming C1q
- Type II: associated with autoimmune phenomenon with autoantibodies to C1-INH molecule
- Both AAE types with ↓ C1q (unlike HAE), ↓ C4/C2
- Treatment: requires much higher amounts of C1-INH concentrate than in HAE during acute attack
| | | | | | | Type | | C1-INH Level | | C1-INH Function | | C4 | | C1q | | | HAE, type 1 | | ↓ | | ↓ | | ↓ | | Normal | | | HAE, type 2 | | Normal to ↑ | | ↓ | | ↓ | | Normal | | | AAE, type 1 | | ↓ | | ↓ | | ↓ | | ↓ | | | AAE, type 2 | | ↓ | | ↓ | | ↓ | | ↓ |
| | | | | |
|
Erythema Annulare Centrifugum (EAC) (Figure 3.23A) - Figurate erythema due to infection (especially dermatophyte), medication, neoplasm or idiopathic
- Presents with annular or polycyclic erythematous plaques with ‘trailing’ scale at inner border, infiltrated peripheral border; expands centrifugally with central clearing
- Histology: focal parakeratosis, superficial and deep perivascular mononuclear infiltrate with characteristic ‘cuffing’ or ‘coat sleeving’ fashion
- Treatment: treat any underlying disorder, topical corticosteroid
Erythroderma- Generalized erythema with scaling, ± systemic manifestations (tachycardia, loss of fluid/protein, etc.)
- Several etiologies including atopic dermatitis, psoriasis, cutaneous T cell lymphoma (CTCL) or drug reaction
- Histology/treatment: dependent on underlying cause
| | Figure 3.21
A: Urticaria
(Reprint from Misery L,
Stander S, eds. Pruritus.
London: Springer; 2010)
B: Dermographism |
|
