A rare hematologic disease characterized by increased levels of methemoglobin in the blood due to exposure to oxidizing agents like nitrates or nitrites, a variety of medications (most commonly local anesthetics), or aniline dyes, among others. Clinical manifestations include cyanosis, dizziness, headache, dyspnea, confusion, and coma. The severity of symptoms ranges from mild to life-threatening, depending on the percentage of methemoglobin. [from
ORDO]