Asthma and rhinoconjunctivitis comorbidity: united airway disease or inherited target organs?

The idea of a united airway disease for asthma and rhinoconjunctivitis is supported by clinical and epidemiological data. However, many asthmatics do not have rhinoconjunctivitis and vice versa. The aim of this study was to investigate if the family history of a specific organ involvement is associated with the implication of the same organ in the allergic child. According to the organ involvement in either or both parents, the family history of 739 children who were skin prick positive to either Dermatophagoides pteronyssinus or D. farinae or both was defined as: asthma and rhinoconjunctivitis positive; asthma and rhinoconjunctivitis negative; asthma negative and rhinoconjunctivitis positive; and asthma positive and rhinoconjunctivitis negative. Asthma and rhinoconjunctivitis in the children were defined according to the International Study of Asthma and Allergies in Childhood questionnaire. Associations between each type of family history and the presence of asthma and/or rhinoconjunctivitis in the children were calculated and adjusted for usual confounders. Adjusted odds ratio of children having asthma, when family history included asthma, was 2.48 (1.38-4.45) when it also included rhinoconjunctivitis; and 2.13 (1.12-4.05) when it did not. However, family history of rhinoconjunctivitis was not associated with asthma in the child. Conversely, the odds ratio of children having rhinoconjunctivitis when family history included rhinoconjunctivitis was 1.84 (1.05-3.21) when it also included asthma; and 1.89 (1.23-2.89) when it did not. Family history of asthma was not associated with rhinoconjunctivitis in the child. In a population of children sensitized to mites, the organ or organs (nose and/or lung) which are implicated in parents tend to be also involved in their children.