Clozapine-induced negative myoclonus is not cataplexy.

A 5-month-old boy with trisomy 21 had repair of ventricular septal defect, atrial septal defect, and ligation of a patent ductus arteriosus. Due to severe pulmonary hypertension, NO inhalation was instituted postoperatively. Over the course of next few hours, he developed life-threatening methemoglobinemia. The condition once recognized was corrected with exchange blood transfusion. The management strategy is described with a brief review of the literature.