METHEMOGLOBIN REDUCTASE DEFICIENCY IN A CAT

During ovariohysterectomy of a 6-month-old domestic shorthair cat, ext ravasated blood appeared brown. Methemoglobinemia was considered likel y on the basis of discoloration of oxygenated blood. The absence of cl inical signs of toxicosis, inability to identify a source of oxidant t hat could cause methemoglobinemia, and persistence of cyanotic-appeari ng tongue and mucous membranes in this cat made a drug-induced cause u nlikely, and was suggestive of a congenital disorder. Subsequent analy sis revealed 49.6% methemoglobin (normal, 0 to 1.1%), resulting from e rythrocyte methemoglobin reductase deficiency (21% of normal activity) .