A 58-year-old man from Mumbai presents with progressive muscle weakness, particularly affecting the lower limbs, and difficulty climbing stairs for the past 3 months. He also complains of myalgia and fatigue. On examination, proximal muscle weakness is noted. Serum creatine kinase is markedly elevated at 3200 U/L. Chest X-ray reveals a 4 cm mass in the left hilum. What is the most likely paraneoplastic syndrome associated with this presentation?