A case of severe methemoglobinemia caused by hair dye poisoning.

CONTEXT: Hair dyes are widely used and very popular xenobiotics. Most of these products contain paraphenylenediamine (PPD) that can cause methemoglobinemia. We here report a case of severe methemoglobinemia that we treated using large amounts of methylene blue. CASE DETAILS: A 30-year-old man visited a regional hospital with cyanosis. He was congenitally blind and had autism. For several weeks, he had mistaken hair dye for toothpaste. When he arrived at a regional hospital, he was drowsy with cyanosis and his initial serum methemoglobin (MetHb) level was 59.5%. After being treated with 2 mg/kg methylene blue (1 mg/kg × 2 administrations), he was transferred to a tertiary university hospital. Upon presentation at the Emergency Department in the tertiary hospital, his MetHb level was found to be 49.4% and his oxygen saturation was 80%. He was then admitted to the intensive care unit. After treatment with 4 mg/kg methylene blue (1 mg/kg × 4 administrations), he successfully recovered. DISCUSSION: Because PPD can result in serious methemoglobinemia, clinicians should test it in cyanotic patients who have been exposed to hair dye for an extended period.