Atopy is a genetic or familial tendency to develop common allergic diseases such as asthma, hay fever and eczema. Historically it was considered to occur in those prone to develop excessive amounts of allergy-specific IgE antibodies. The atopy pattern commences in early childhood with food allergies (cow’s milk, egg and peanut) associated with infantile eczema, then progresses onto childhood asthma and finally rhinitis and hay fever in the teenage years.
Recent studies show specific sub-groups within the atopic population with different patterns of reactivity. Four distinct childhood atopic groups (or phenotypes) have emerged:
- Sensitive to House Dust Mite only (17%) presenting with eczema, asthma and rhinitis
- Late-onset mixed inhalant allergies (11%) strongly association nasal allergy
- Mixed food and inhalant allergies (4%) strongly associated severe asthma
- No allergy (68%) those unlikely to develop childhood asthma, eczema or rhinitis
Similarly “phenotypes” in childhood asthma have been described such as the transient wheezy infant, the non-atopic but wheezy toddler, IgE-related asthma and then late-onset non-allergic asthma. Further subdivision into patho-physiological” endotypes” include allergic asthma, aspirin sensitive asthma, broncho-pulmonary aspergillosis and asthma, gastro-oesophageal reflux related asthma, non-allergic asthma, all with differing underlying patho-physiologies and biomarkers. There are groupings linked to childhood obesity, vitamin D deficiency, cold or exercise-induced wheeze and virus or rhinitis-related asthma. Asthma is no longer considered to be a single disease entity but a heterogenous group of wheezing disorders all with hyper-reactive airways and bronchospasm but from differing causes.
Reference: Atopy phenotypes in Childhood Asthma Prevention Study (CAPS) cohort and the relationship with allergic disease. Garden FL, Simpson JM, Marks GB, Clinical and Exp Allergy 2013 43 633-641
