A Case Report of Acquired Methemoglobinemia in a Neonate Complicated by G6PD Deficiency

Methemoglobinemia is an uncommon cause of cyanosis in infants, occurring when the iron in hemoglobin is oxidized from the ferrous (Fe2+) to the ferric (Fe3+) state, which impairs oxygen transport and leads to tissue hypoxia. This report discussed a case of acquired methemoglobinemia in a newborn complicated by an underlying glucose-6-phosphate dehydrogenase (G6PD) deficiency, a rare association.

A 20-day-old male newborn exhibited lethargy, fever, diarrhea, jaundice, and dark urine after receiving ofloxacin for diarrhea. Upon examination, he displayed signs of shock, cyanosis, and respiratory distress, although his abdomen, chest, and cardiovascular system appeared normal.

Despite increasing the fraction of inspired oxygen (FiO2) and providing supportive care for shock, the infant's oxygen saturation (SpO2) did not improve. Tests including a chest X-ray, hyperoxia test, and echocardiography ruled out cyanotic heart or lung conditions. Arterial blood gas analysis indicated a PaO2 greater than 100 mmHg with an SpO2 of 84%. Co-oximetry revealed a methemoglobin level of 25.9%, and low G6PD levels prevented the use of methylene blue for treatment. The infant was treated with high doses of Vitamin C and received a blood transfusion, leading to recovery.

To summarize, methemoglobinemia should be considered when an infant presents with unexplained hypoxia and cyanosis that does not improve with oxygen therapy. It is crucial to rule out G6PD deficiency before administering methylene blue.

Source: Aggarwal S, Garg S, Sehgal M, Jain B, Jagpreet S. Methemoglobinemia and Glucose-6-phosphate Dehydrogenase Deficiency in a Neonate. Indian Pediatrics Case Reports 5(1):p 12-14, Jan–Mar 2025. | DOI: 10.4103/ipcares.ipcares_29_24