A mentally retarded male adolescent who has been increasingly aggressive and agitated receives several consecutive IM doses of haloperidol, totaling 30 mg in 24 hours, as a chemical restraint. The next day, he is rigid, confused, and unresponsive. His blood pressure is 150/95 mm Hg, his pulse is 110 beats/min, and his temperature is 38.9°C (102°F). Both his WBC count and CPK levels are very high. Which of the following is the most likely diagnosis?

a. Acute dystonic reaction

b. Neuroleptic-induced Parkinson disease

c. Malignant hyperthermia

d. Neuroleptic malignant syndrome

e. Catatonia