Naphthalene-Induced Methemoglobinemia With Acute Hemolysis in a Child: A Rare Case of Refractory Hypoxia

Methemoglobinemia is a rare but potentially life-threatening condition caused by oxidation of hemoglobin iron from the ferrous to ferric state, impairing oxygen delivery to tissues; early recognition is crucial as clinical manifestations may be disproportionate to pulse oximetry readings. We describe a case of a three-year-old female child who presented with acute onset cyanosis and hypoxia unresponsive to supplemental oxygen, despite a normal cardiopulmonary examination and persistently low oxygen saturation on pulse oximetry. Blood gas analysis revealed a discrepancy between low oxygen saturation and oxygen levels, raising suspicion of methemoglobinemia, which was subsequently confirmed by elevated methemoglobin levels. The child was managed with prompt supportive care, including high-flow oxygen therapy, followed by intravenous methylene blue, due to significant symptoms and elevated methemoglobin levels, which resulted in rapid clinical and biochemical improvement. She made a complete recovery without residual complications. This case underscores the importance of considering methemoglobinemia in young children presenting with unexplained hypoxia refractory to oxygen therapy, as timely diagnosis and appropriate treatment can be life-saving.