A male neonate born at 33 weeks of gestation was orally administered caffeine from the 2nd to the 13th days of life for the management of apnoea of prematurity with several episodes of bradycardia. Paroxysmal bradycardia recurred at 23 days of age, indicating that the treatment was ineffective. A physical examination at 31 days of age revealed no hypothermia or other abnormalities. Laboratory findings at 35 days of age showed no abnormalities in the serum electrolyte, thyroid hormone, creatinine kinase, or troponin-I levels. The serum samples were also negative for Anti-SS-A and anti-SS-B antibodies. Other serum findings were as follows: epinephrine, 17 pg/mL (normal < 100 pg/mL); norepinephrine, 1205 pg/mL (normal < 450 pg/mL); and dopamine, 38 pg/mL (normal < 20 pg/mL). The urinary metanephrine-to-creatinine ratio was 2.06 (normal < 0.5). The chest radiography, echocardiography, brain magnetic resonance imaging and video electroencephalography findings were normal. His resting heart rate was 150-170 beats/