What does the shape of chronic spontaneous urticaria wheals tell us?

Chronic spontaneous urticaria (CSU) affects around 1% of the population and the skin eruptions associated with it take a variety of forms. It greatly impacts a patient’s quality of life, and is still poorly understood. Studies investigating its dynamics in vivo are rare. A new study suggests that it may be possible to understand the molecular processes involved based on the morphology of the rashes, called wheals.Japanese researchers have developed a mathematical model that identifies the mechanisms behind which wheals appear in CSU patients, based on their geometric shape.The researchers' modeling first identified five wheal patterns: annular, broken annular, geographic, circular and spotted. To validate the model, they compared these computer-simulated rash patterns with images from 105 patients with CSU who visited the department of dermatology at Hiroshima University Hospital. The data were then analyzed by six dermatologists, who reliably classified 87.6% of the samples into one of the morphological categories. Wheals with geographic (50% of cases) and circular (25% of cases) patterns were the most common.Read: Risankizumab remains effective for long-term treatment of psoriasisCSU is known to occur when a triggering factor leads to the degranulation of mast cells and basophils. These release pro-inflammatory mediators, including histamine. This process also increases the expression of tissue factor (TF) on vascular endothelial cells. Analyses of skin samples in vitro have revealed that the shape of skin rashes is a reflection of the pathophysiological dynamics at work beneath the skin.Each of these stages seem to influence the geometry of the lesions on the skin. "Our network analysis revealed that the coagulation status likely determines boundary/area pattern of wheals, while the state of spontaneous histamine release from mast cells may contribute to the divergence of size and outline of the eruptions," the researchers wrote in their paper. This would explain why a treatment’s efficacy varies according to the mechanism targeted. "In fact, antihistamines are effective for 70%-to-80% of CSU patients, but certain patients refractory to antihistamines respond well to anticoagulants and protease inhibitors," the researchers state. "Thus, our approach, which proposes a pathophysiological in vivo network considering both topological and kinetical reactions in the skin, is expected to suggest a patient-specific treatment based on the geometry of skin eruptions."Such a mathematical model could be applied to other dermatological conditions characterized by the formation of geometric lesions, such as psoriasis, body ringworm, erythema multiforme, autoimmune bullous dermatoses or erythema gyratum repens.The paper was published in Communications Medicine.Read: Dermatology images database including diverse skin types in its beta versionThis article was translated from French and originally ran in our sister publication Profession Santé.

What does the shape of chronic spontaneous urticaria wheals tell us?

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