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A 66-year-old man presented with gradually increasing dyspnoea and reduced exercise tolerance. There was no chest pain or any other respiratory symptoms, he had never smoked and there was no occupational exposure to dusts, toxins or asbestos. He also complained of a dull pain and numbness in his left forearm, unrelated to exertion. Previous medical history included ischaemic heart disease and parkinsonism which was unresponsive to escalating therapy. Medication on presentation included aspirin 75 mg, pergolide 1 mg three times daily and two Sinemet plus three times daily. He was apyrexial and tachypnoeic (respiratory rate 32/min), oxygen saturation 89% on air, the peak expiratory flow rate was 140 litre/min, heart rate 82 beats/minute and bloot pressure 143/66 mmHg. The jugular venous pressure was not raised and there was poor lung expansion with florid, bibasal, late inspiratory crackles to the midzones. He was bradykinetic with a marked coarse, jerky resting tremor in the left upper limb with quasi-purposeful involuntary movements and marked apraxia. There was greatly increased axial tone. No limb weakness was demonstrated, reflexes were unremarkable and the plantar response was flexor. There was sensory impairment in the left arm and leg to all modalities. His gait was bradykinetic and shuffling with retropulsion on stopping. He had a full range of eye movements with unrestricted vertical gaze. Full blood count, urea and electrolytes, liver function tests, calcium and creatine kinase were all normal. His C-reactive protein level was 63 mg/litre and erythrocyte sedimentation rate was 45mm/hr. Arterial blood gas analysis on air revealed; partial pressure of arterial oxygen (PaO2) 7.2 Kpa, partial pressure of arterial carbon dioxide (PaCO2) 2.6 Kpa, pH 7.52, base excess 2, bicarbonate 26 mmol. An electrocardiogram showed sinus rhythm with Q waves in III and aVf. Chest X-ray showed bilateral extensive subpleural interstitial changes and honeycombing with loss of volume particularly in the right lung (Figure 1). High resolution computed tomography of the thorax demonstrated widespread bilateral reticular shadowing suggestive of fibrosis, honeycomb changes and associated basilar traction bronchiectasis. Lung function tests demonstrated a forced expiratory volume in 1 second (FEV1) 1.41 litres (52% of predicted), forced vital capacity (FVC) 1.45 litres (43% of predicted), FEV1/FVC 97% and gas transfer factor (DLCO) 17.4 (70% of predicted). He was treated with oxygen and antibiotics. Transbronchial biopsy with histology demonstrated diffuse fibrous tissue, with no evidence of infection, tuberculosis or malignancy. Bronchoalveolar lavage revealed a neutrophilia. Microbiology cultures were negative. His antinuclear antibody, complement levels, classical antineutrophil cytoplasmic antibody, rheumatoid factors, Scl-70 and Jo-1 antibodies were normal. Reviewing his medication with pharmacy led to the discontinuation of pergolide since it has been reported to cause diffuse interstitial pulmonary fibrosis. A consultant neurological review was sought and a diagnosis of corticobasal degeneration made. He was discharged on home oxygen. After 1 month of discontinuing pergolide, the patient subjectively noticed improvement in his dyspnoea, reflected in an increase in DLCO (82% predicted).