As the chill of the Scottish autumn set in, a 43-year-old man went to see a family doctor in 2016. For about the last three months, he was constantly tired and out of breath. The physician at the Aberdeen Royal Infirmary in Scotland thought the patient — who worked a desk job and didn’t smoke cigarettes — had an infection in his lower respiratory tract.

At first the man got better. But then it got so bad that the patient had to take 14 days off work. The doctor looked at the man’s blood count, kidney and liver function, and took a chest radiograph — all of which seemed normal.

Stumped, he called his colleague, Dr. Owen Dempsey, a pulmonologist at the infirmary. Dr. Dempsey swiftly called the patient, who was breathless even upon picking up the phone.

Patient histories are important, Dr. Dempsey said, so he was “suitably nosy and asking about his domestic setup.”

Were there pets in the home?