Localized salt-dependent aquagenic urticaria: a subtype of aquagenic urticaria?

Evidence for histamine release in chronic inducible urticaria – A systematic review

Background

Chronic inducible urticaria (CIndU) constitutes a group of nine different CIndUs in which pruritic wheals and/or angioedema occur after exposure to specific and definite triggers. Histamine released from activated and degranulating skin mast cells is held to play a key role in the pathogenesis of CIndU, but evidence to support this has, as of yet, not been reviewed systematically or in detail. We aim to characterize the role and relevance of histamine in CIndU.

Methods

We systematically searched 3 electronic databases (PubMed, Scopus, and Embase) for studies that reported increased serum or skin histamine concentration (direct evidence) or in vitro or ex vivo histamine release (indirect evidence) following trigger exposure.

Results

An initial total of 3,882 articles was narrowed down to 107 relevant studies of which 52 were in cold urticaria, 19 in cholinergic urticaria, 14 in heat urticaria, 10 in contact urticaria, 7 each in solar urticaria and vibratory angioedema, 4 each in symptomatic dermographism and aquagenic urticaria, and 3 in delayed pressure urticaria. The results of our review support that histamine has a key pathogenic role in the pathogenesis of all CIndUs, but it is not the sole mediator as evidenced by the often poor relationship between the level of histamine and severity of symptoms and the variable clinical efficacy of H1-antihistamines.

Conclusions

Histamine released from skin mast cells is a key driver of the development of signs and symptoms and a promising therapeutic target in CIndU.

Aquagenic urticaria: Water, friend, or foe?

There are <100 reported cases of aquagenic urticaria. Although most are sporadic, several diseases have been associated. Diagnosis is based on provocation tests. Second-generation antihistamines are the first-line treatment.

Case of aquagenic urticaria: Case report and the results of histopathological examination

Aquagenic urticaria (AU) is a rare skin condition in which dermal contact with water serves as a trigger of urticaria and pruritus. To make a diagnosis, a water challenge test is useful. We herein report a 16-year-old Japanese boy diagnosed with AU by water provocation test. The induced skin lesion histologically showed prominent degranulation of mast cells and lymphocytic infiltration throughout the dermis. This is the second report documenting the histopathological features of AU.

Water-related dermatoses

Water-related dermatoses are a spectrum of diseases that are associated with water exposure. They result either from the direct influence of water or after injury from water inhabitants. In this review, clinical entities that manifest after water exposure (aquagenic pruritus, aquagenic urticaria, and aquagenic wrinkling of the palms) will be discussed with particular focus on the reported pathogenesis. Aquatic organisms and activities can be linked to cutaneous injuries that require identification and distinct management. Marine and freshwater dermatoses were summarized to provide physicians with easy access to the causative organism, method of injury, and appropriate management.

Aquagenic urticaria: diagnostic and management challenges

Aquagenic urticaria (AU) is a rare inducible form of physical urticaria, which occurs in response to cutaneous exposure to water, including sweat and tears. Patients present with characteristic 1–3 mm folliculocentric wheals with surrounding 1–3 cm erythematous flares within 20–30 minutes following skin contact with water. In rare cases, there are concomitant systemic symptoms, such as wheezing or shortness of breath. The pathogenesis of AU is poorly understood at this time, and it appears to be mediated in both a histamine-dependent and independent manner. Diagnosis is based on eliciting a thorough clinical history combined with a water challenge test. Some patients may need to undergo further testing to exclude other physical urticarias. Rarely, multiple physical urticarias can be present in one patient, which can complicate diagnosis and treatment. Currently, the first-line therapy for AU is an oral administration of nonsedating, second-generation H₁ antihistamines, but many patients may require further interventions to have adequate symptomatic control. In this review, we discuss the diagnostic and management challenges of AU. We review the key diagnostic features that differentiate AU from other physical urticarias. We additionally describe a therapeutic ladder for the treatment of AU and the rationale supporting these treatments.