MRCP2-0804

MRCP2-0804

A 67-year-old female presents to respiratory outpatients with an 8-week history of gradually worsening shortness of breath. Her exercise tolerance has reduced to 50 yards from several miles; she reports chronic lower back pain but no other symptoms. Her past medical history includes type 2 diabetes mellitus, psoriasis, recurrent urinary tract infections and ischaemic heart disease. She currently takes metformin 500 mg BD, bisoprolol 2.5 mg OD, aspirin 75 mg OD, atorvastatin 40 mg ON, ramipril 2.5 mg and nitrofurantoin 50 mg ON with no change in the last 6 months. She has never smoked, has no pets and works as a secretary.

On examination, the patient is breathless on minimal exertion. Observations are normal, there is no clubbing and she has fine end-inspiratory crepitations at both bases. A CT chest shows ground glass changes with minimal honey combing at both bases. What is the most likely cause of her underlying respiratory condition?