A 6-year-old unvaccinated child from rural India presents with a 3-day history of sore throat, low-grade fever, and progressive difficulty in swallowing. On examination, a thick greyish-white pseudomembrane is seen covering the soft palate and extending to the pharynx, with a foul-smelling discharge. The child has cervical lymphadenopathy with "bull neck" appearance. Which of the following is NOT a recognized complication of diphtheria?