Treating a recurring chest infection

A health-conscious patient presents with recurrent chest infection. What’s the underlying cause?

Jan is a 48-year-old teacher’s assistant at the local state high school. She developed type 1 diabetes as a teenager and was recently found to have autoimmune hypothyroidism.

In childhood, she had asthma, but has not required inhalers for some years and has never been hospitalised with it. She is very health conscious and manages her diabetes well.