A 47-year-old female with shortness of breath and "reversed halo sign".

A 47-yr-old female was referred to a tertiary centre for further evaluation of chronic cough, fever, progressive exertional dyspnoea and fatigue. From a respiratory point of view she had been well until 7 months previously when she had started to experience systemic fatigue, low-grade fever and chronic dry cough. A computed tomography scan of the chest demonstrated diffuse bilateral ground-glass, ill-defined pulmonary opacities affecting all lobes. Some had central ground-glass hazy density with peripheral areas of increased opacity, which is consistent with "reversed halo sign". Cryptogenic organising pneumonia (COP) is a clinical, radiological and pathological diagnosis which is made when no definite cause, such as infection or connective tissue disease, is found. It is characterised histopathologically by the presence of patchy distribution of granulation tissue, which consists of fibroblasts and myofibroblasts embedded in a loose connective matrix, present in the lumen of the distal airspaces including alveoli, alveolar ducts and bronchioles. This case report illustrates the association of the reversed halo sign with COP. Although only seen in one fifth of patients with the disease, it appears to suggest the diagnosis of COP and, with proper clinical correlation, it may be another diagnostic adjunct.