1.1.1.1 Urticaria

Hives, wheals, weals.

Acute urticaria: Life prevalence around 8-2%. For non-acute urticaria, around 0.1-0,6% in the general population.

Urticaria is a group of diseases characterized by the development of wheals (hives), angioedema (see chapter 1.1.2), or both. Hives are defined as pruritic transient swellings of the upper dermiswith multiple causes, usually mediated mainly by histamine release.

Urticaria needs to be differentiated from other medical conditions where wheals, angioedema, or both can occur, e.g. anaphylaxis, autoinflammatory syndromes, urticarial vasculitis, orbradykinin-mediated angioedema including hereditary angioedema (HAE).

Urticaria is a mast cell-driven disease. Release of histamine and other mediators such as platelet-activating factor (PAF) and cytokines released from activated skin mast cells, result invasodilatation and plasma extravasation as well as sensory nerve activation and cell recruitmentto urticarial lesions.

The mast cell-activating signals in urticaria are ill defined and likely to be heterogeneous and diverse (IgE-mediated Type I-reaction, non specific histamine liberators, activation of complement, autoimmune mediated urticaria - IgG against IgE or against high affinity IgE-receptor and IgE against autoantigens, as well as other poorly understood mechanisms).

Wheal: Central swelling of variable size surrounded by reflex erythema, and a fleeting nature, with the skin returning to its normal appearance, usually within 30 minutes to 24 h. Itching or sometimes burning sensation.

Urticaria may be associated with angioedema: Pronounced erythematous or skin colored swelling of the lower dermis and subcutis or mucous membranes. Resolution slower than that of wheals (can take up to 72 hours). Sometimes pain, rather than itch.
 

Sudden appearance of erythematous lesions and hives whose appearance varies over the course of a few hours. Marked pruritus. If individual hives persist for more than 24 hours, the possibility of urticarial vasculitis must be considered (skin biopsy may be useful).

Hives can appear in any part of the cutaneous surface, showing variable size and extension. In some forms of urticaria the lesions may be papular (e.g. cholinergic urticaria). Angioedema commonly affects eyelids and lips, hands and feet. 

The spectrum of clinical manifestations of different urticaria subtypes is very wide. Two or more different subtypes of urticaria can coexist in any given patient.

• Acute spontaneous urticaria: Occurrence of spontaneous wheals, angioedema or bothfor less than 6 weeks.
• Chronic spontaneous urticaria: appearance of wheals, angioedema or both for > 6 weeks due to known or unknown causes.
• Acute or chronic Inducible Urticaria include: symptomatic dermographism, cold urticaria,  delayed  pressure  urticaria,  solar  urticaria,  heat  urticaria,  vibratory angioedema, cholinergic urticaria, contact urticaria and aquagenic urticaria.

Based on aetiology.

• Immunological:
  1. IgE-mediated (Type I Reaction) foods, medications, bee or wasp toxins, foreign proteins and other exogenous materials such as latex or plant products (contact urticaria).
  2. Immune complex-mediated (Type III Reaction).
  3. Autoimmune (autoantibodies against IgE or the FcE-receptor or IgE againstautoantigens).a
• Non-immunologic:
  1. Direct mediator release from mast cells: caused by foods/food additives/ medications.
  2. Physical forms (pressure, heat, vibration).
  3. intolerance of NSAID (non-steroidal anti-inflammatory drugs).
• Underlying diseases such as intestinal parasites, foci of infection, thyroid disease, liver disease (viral hepatitis), other viral infections, connective tissue disorders.
• Idiopathic

Acute urticaria: Does not require a diagnostic workup, as it is usually self-limiting. Choice based on history and clinical findings, could include prick testing for medications and foods, if relevant.

Chronic Spontaneous Urticaria: Limited investigations are recommended: FBC, automated chemistry, CRP and/or ESR. In patients with long-standing and/or uncontrolled disease, furtherdiagnostic procedures based on the patient history and examinations could be recommended.

Standardized provocation testing to diagnose chronic inducible urticaria are required for an accurate diagnosis.

Edema of the upper and mid dermis is the prevalent histological feature, perivascular inflammatory infiltrate of variable intensity depends on different subtypes, consisting mainly oneosinophils and lymphocytes, occasional neutrophils with or without basophils. No vascular damage. 

Acute urticaria: Self-limiting.

Chronic spontaneous Urticaria: Unpredictable. Spontaneous remissions. Variable remission rates (45% at 5 years).

Several factors have been associated with a long duration in chronic spontaneous urticaria: 1.disease activity, 2. angioedema, 3. combination of chronic spontaneous urticaria with inducible urticaria and 4. autoreactivity (positivity in the autologous serum skin test). 

Anaphylactic shock should be considered in some type of urticaria as allergic acute urticaria,acquired cold urticaria or cholinergic urticaria. Not common in Chronic Spontaneous Urticaria.

Clinical.

Urticarial vasculitis (individual hives persist for more than 24 hours), maculopapular exanthems, maculo-papular cutaneous mastocytosis (formerly called urticaria pigmentosa), urticaria syndromes (see chapter xx), auto-inflammatory syndromes (e.g. cryopyrin-associated periodic syndromes or Schnitzler's syndrome), non-mast cell mediator-mediated angioedema (e.g.bradykinin-mediated angioedema), Sweet's syndrome, erythema multiforme.

• Acute urticaria - systemic: non-sedating H1-antihistamines. If severe, consider shortcourse of systemic corticosteroids.
• Chronic spontaneous urticaria:
  • To identify and eliminate underlying cause(s) and/or eliciting trigger(s).
  • Non-sedating second generation H1-antihistamines at licenced doses and at higher dose. In refractory cases, the recommendation is to add anti-IgE therapy,nowadays omalizumab. Ciclosporin could be recommended if omalizumab fails partially or completely. A good number of alternative treatments can beconsidered e.g methotrexate or some special diets.