A 12-year-old girl is brought to your primary care center by her parents for having fever, joint pains and a rash. The pain moves from joint to joint. Her parents are particularly concerned about involuntary, uncoordinated movements of her tongue, face and upper extremities. On review of systems, you discover that he suffered from a sickness 2 to 3 weeks ago, which was assumed to be a viral infection and treated with acetaminophen and fluids. Physical examination is notable for involuntary movements in the face and upper extremities. When you asked the patient to squeeze your hand, she made repetitive irregular squeezes. There are subcutaneous nodules on both upper and lower extremities. You also noticed branching erythematous ring-shaped rash over the extremities. As you discuss the diagnosis with the girl and her parents, the parents asked you about the most feared complication of this disorder. Which of the following disorders is the most serious complication of this disease?
