Lady with purple Hands

A 79-year-old woman with recurrent urinary tract infections presented with complaints of “purple” hands.

Bluish-purple discoloration of skin involved her earlobes and hands. The pulse oximeter read 80% to 84% saturation while 100% oxygen was administered at a flow of 15 L/min. Her urine was deep orange, and arterial blood appeared dark brown. Arterial blood oximetry showed a PO2 of 200 mm Hg, with 87.5% oxyhemoglobin and 11.8% methemoglobin. She had normal glucose-6-phosphate dehydrogenase levels, and intravenous methylene blue improved her cyanosis; her methemoglobin levels decreased to 0.3%. Apparently, acquired methemoglobinemia and urine discoloration had been induced by 10 days of phenazopyridine use (200 mg 3 times daily) for urinary tract infection. Urine returned to normal color within 3 days of discontinuing phenazopyridine. This azo dye, often used as a topical urinary tract analgesic, should not be administered for more than 2 days because of potential adverse effects (cytopenias, methemoglobinemia, nephrotoxicity, orange urine discoloration, and transaminitis).1

Methemoglobinemia is caused by excess methemoglobin (normal ≤1% of total hemoglobin) that is formed by oxidation of the iron moiety of hemoglobin from ferrous (normal) to ferric state. Drugs or chemicals, hemoglobin M variants, and congenital diminished activity of erythrocytic NADH-cytochrome-b5 reductase are associated with methemoglobinemia.2 Avoidance or discontinuation of offending drugs and use of methylene blue (once normal glucose-6-phosphate dehydrogenase levels have been confirmed) constitute the main management options.