A rare case of congenital methemoglobinemia with severe mitral stenosis: An anesthetic and surgical challenge

Methaemoglobinemia is a condition that occurs when red blood cell contains higher than 1% methaemoglobin (MHb). It can be congenital or acquired. The condition is generally asymptomatic until the serum MHb level reaches as high as 40%. Dyspnea, acidosis, cardiac dysrhythmias, heart failure, seizures, and coma may occur at levels exceeding 45%, and a high mortality rate is seen with levels above 70%. We report a rare association of a case of rheumatic heart disease with severe mitral stenosis with congenital methemoglobinemia diagnosed incidentally during mitral valve replacement procedure under cardiopulmonary bypass.