MRCP2-2255
A 68-year-old man presents with severe intractable back pain, headaches, and lethargy. He recently had left lower lobe pneumonia and his symptoms have significantly worsened over the past few days. He is unable to keep any food or fluids down and is vomiting several times during the day. On examination, his BP is 160/95 mmHg and he looks pale. His pulse is 88/min and regular and there are bilateral crackles on auscultation of the chest. Investigations reveal a low haemoglobin level, high potassium and creatinine levels, and positive P-ANCA. What is the most likely diagnosis?