Summary

We report the case of a 12-year-old girl with an allergic bronchopulmonary aspergillosis (ABPA), intermediate sweat chloride tests and one cystic fibrosis (CF)-causing mutation, p.Phe508del. After extensive screening of the CF transmembrane regulator (CFTR) gene, she finally was found to carry a rare deep intronic mutation (c.872-1110_1113delGAAT), which confirmed the atypical mild CF disease. Although a classical steroid treatment did not allow the healing of the ABPA, an omalizumab therapy led to a long-term recovery. This case emphasises the need to search for rare CFTR gene mutations as far as possible when a CF disease is evocated. Moreover, it also highlights that although omalizumab is not yet recognised as a classical ABPA treatment in CF, it should be considered as an alternative therapy in steroid-resistant patients.