The Multiple Trajectories of the Allergic March.

The allergic march comprises the sequential appearance of a series of allergic comorbidities. However, variability in the onset and progression of allergic diseases generates a heterogeneous scenario that does not follow a linear and single trajectory. Almost half of the pediatric population presents at least 1 allergy symptom. However, only 4%-6% present multimorbidity, with several allergic diseases co-occurring. It has recently been shown that although they share etiological mechanisms and risk factors, allergic diseases arise independently. In most cases, progression is not consecutive, or at least not the same in all patients. TH2-mediated inflammation, epithelial barrier dysfunction, and genetic predisposition play a fundamental role in the etiology of allergic diseases, on which the interaction with the exposome acts decisively. Therefore, studying diseases from an omics point of view is essential when attempting to describe the various trajectories of allergic progression and to propose effective interventions to prevent multimorbidity. In this narrative review, we provide an overview of the current perception of the allergic march, including clinical observations, omics data, risk factors, and measures aimed at modifying its course or even preventing its onset.

The Multiple Trajectories of the Allergic March

The allergic march comprises the sequential appearance of a series of allergic comorbidities. However, variability in the onset and progression of allergic diseases generates a heterogeneous scenario that does not follow a linear and single trajectory. Almost half of the pediatric population presents at least 1 allergy symptom. However, only 4%-6% present multimorbidity, with several allergic diseases co-occurring. It has recently been shown that although they share etiological mechanisms and risk factors, allergic diseases arise independently. In most cases, progression is not consecutive, or at least not the same in all patients. TH2-mediated inflammation, epithelial barrier dysfunction, and genetic predisposition play a fundamental role in the etiology of allergic diseases, on which the interaction with the exposome acts decisively. Therefore, studying diseases from an omics point of view is essential when attempting to describe the various trajectories of allergic progression and to propose effective interventions to prevent multimorbidity. In this narrative review, we provide an overview of the current perception of the allergic march, including clinical observations, omics data, risk factors, and measures aimed at modifying its course or even preventing its onset. (AU)

La marcha alérgica ha dado respuesta durante mucho tiempo a un escenario de aparición secuencial de diferentes comorbilidades alérgicas. Sin embargo, la variabilidad en la aparición y progresión de las diferentes enfermedades alérgicas dibuja un escenario heterogéneo que no responde a una trayectoria lineal y única. Aunque en la actualidad casi la mitad de la población infantil presenta al menos un síntoma de alergia, tan solo un 4-6% presenta multimorbilidad, coexistiendo varias entidades alérgicas. Recientemente se ha demostrado que, aunque compartiendo mecanismos etiológicos y factores de riesgo, estas enfermedades alérgicas surgen de manera independiente y que, en la mayoría de los casos, no se observa una progresión consecutiva, o al menos, no la misma en todos los pacientes. La inflamación mediada por células T helper de tipo 2 (Th2), la disfunción de la barrera epitelial y la predisposición genética juegan un papel fundamental en la etiología de estas enfermedades, sobre los que actúan de manera determinante la interacción con el exposoma. Por ello, el estudio de las enfermedades, desde un punto de vista de las ómicas, es fundamental para describir las diferentes trayectorias de la marcha alérgica y proponer intervenciones eficaces para evitar escenarios de multimorbilidad. En esta revisión narrativa se incluye una descripción general de la percepción actual de la marcha alérgica, incluidas observaciones clínicas, datos ómicos, factores de riesgo y medidas preventivas propuestas para modificar su curso o incluso prevenir su aparición. (AU)