Methemoglobinemia Caused by P-nitroaniline Intoxication: Report of Four Case

Methemoglobinemia can be induced by exposure to p-nitroaniline, an intermediate in dyeing and finishing industrial processes. Methemoglobinemia can be fatal if the chemical exposure is acute and at high dose. Here we report four cases involving acute exposure to p-nitroaniline while packing material into barrels. The patients presented with cyanosis, dizziness, nausea, vomiting, general weakness, chest tightness, dyspnea, and urine that was yellow and fluorescent. The perception of tightness of chest responded to one shot of methylene blue. One patient had confused mental status. Blood concentrations of methemoglobin at presentation were between 34.6% and 62.5%, returning to normal range in two days. Investigation of the packing area was conducted to understand how the four workers were exposed to the chemical, as well as degree of exposure. This event provides good lessons for people working in relevant industry and for healthcare professionals.