Microbial clues lead to a diagnosis of cystic fibrosis in late adulthood.

Cystic fibrosis (CF) is the most common life-limiting autosomal recessive genetic disorder among Caucasian populations. The majority of CF cases are diagnosed in childhood; however, increasing numbers of adults are being diagnosed with the condition. We present the case of a 65-year-old Irish woman presenting with a chronic cough and a history of recurrent respiratory tract infections. Staphylococcus aureus, Scedosporium apiospermum and Stenotrophomonas maltophilia were grown from bronchoalveolar lavage raising suspicion for CF. Sweat testing was negative; however, genetic testing revealed the presence of ∆F508 and R117H CF mutations, the latter mutation conferring a milder form of CF. The patient commenced treatment with the cystic fibrosis transmembrane conductance regulator (CFTR) potentiator medication ivacaftor to good effect. Novel CFTR potentiators and modulators have significant potential to benefit morbidity and mortality in this group. In this case, the microbiological results were key in pursuing genetic testing and diagnosing CF. © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.