Asthma and allergy development in mono-zygotic twins discordant for severe respiratory syncytial virus infection in infancy

Background:

Children recovering from severe Respiratory Syncytial Virus (RSV) bronchiolitis are at increased risk of recurrent wheeze, asthma and possible allergy in later childhood. It is difficult to differentiate causes of disease from consequences, especially in complex genetic diseases influenced by environmental exposures.

Aim:

To compare the long-term outcome of pulmonary function, sensitization and clinical diagnosis of asthma in monozygotic (MZ) twin pairs discordant for hospitalization with verified severe RSV infection in infancy.

Methods:

Clinical examination was conducted on 37 MZ twin pairs (mean age 7.6 years) discordant for hospitalization with severe RSV infection in infancy. Asthma was assessed by interview, lung function (baseline spirometry for schoolchildren and specific airway resistance for preschool children), airway reactivity (responsiveness to metacholine for schoolchildren and dry air hyperventilation for preschool children), fractional exhaled nitric oxide (FeNO), and sensitization (skin testing to common inhalant allergens).

Results:

7 years (mean) after the severe RSV infection there were no differences within the discordant MZ twin pairs with respect to lung function, airway reactivity, FeNO, sensitization or clinical asthma (p > 0.1 for all comparisons).

Conclusion:

We found no difference on the development of asthma and allergy from having or not having severe RSV infection in infancy within MZ twin pairs. This suggests that severe RSV infection is not causative in the development of asthma or allergy in childhood which is probably caused by other factors in the shared environmental and genetic factors.