A 28-year-old male, previously healthy, had a cold 2 weeks ago. He developed lower limb weakness 3 days ago and bilateral upper limb weakness 2 days ago, unable to maintain a sitting position or lie down independently. Examination: bilateral peripheral facial palsy, flaccid paralysis of all limbs, absent tendon reflexes, and mild glove-and-stocking sensory deficit in the distal limbs. The correct diagnosis is: