Researchers reviewed current literature and compiled best
practices for clinicians diagnosing and treating aquagenic urticaria (AU), a
rare, but debilitating form of the skin disorder that leaves patients unable to
bathe, sweat, or cry without breaking out in painful wheals.
Published in the November issue of the Journal of Asthma and
Allergy, the article presented a practical overview of a challenging process.
Robert Rothbaum and Jean S. McGee of Boston University noted less than fifty
reported cases of a disease whose mechanism is poorly understood. Lacking a
clear pathogenesis, researchers have been unable to devise evidence-based
therapies.
The review outlined existing theories of how one becomes
“allergic to water”. The first postulates that water can combine with sebum
(oily secretions) to create a toxin that would trigger histamine release. Another possibility is increased water
diffusion caused by sudden changes in the follicular osmosis process. In a
third potential explanation, water-soluble antigens on the epidermis trigger
histamine when dissolved by moisture. Lastly, the authors cited a study
highlighting several AU patients who tested negative for any increase in
histamine at water exposure, which suggested there could be a histamine-independent
model.
Diagnosis is a complicated process of differentiation, not
only among other physical types of urticaria (cholinergic, cold, heat, and
pressure), but also in a handful of AU’s own clinical subtypes.
The authors included a table charting a score of common
lookalikes and their distinguishing features, “patients with AU will present
with characteristic 1–3 mm folliculocentric wheals and surrounding 1–3 cm
erythematous flares within 20–30 minutes following skin contact with water.”
Researchers had referred to orally-administered non-sedating
second-generation H1 antihistamines as the cornerstone therapy for AU. Rothbaum
et al charted the known treatment options noting, “Many patients may require
further interventions to have adequate symptomatic control.”
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Rothbaum R, McGee JS. Aquagenic urticaria: diagnostic and
management
challenges. J Asthma Allergy. 2016 Nov 29;9:209-213.
Abstract
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.
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