A 20-year-old woman presents with bilateral conductive deafness, palpable purpura on the legs and hemoptysis. Radiograph of the chest shows a thin-walled cavity in left lower zone. Investigations reveal total leukocyte count 12,000/mm red cell casts in the urine and 12,000/mm serum creatinine 3 ing/dL. What is the most probable diagnosis ?