Cyanosis and congenital methemoglobinemia in a puppy

A six-month-old Pomeranian was referred for evaluation of cyanosis, The pup py had been cyanotic since it was acquired at six weeks of age, but otherwi se appeared normal. Diagnostics were aimed at the most common causes (i.e., congenital defects in the cardiovascular and respiratory systems) of cyano sis in a juvenile animal, No clinically significant abnormalities were dete cted on evaluation of thoracic radiographs, echocardiogram, cardiac color-f low Doppler examination, or blood gases, At this point, a dysfunction in he moglobin was considered as a possibility, Methemoglobinemia due to deficien cy of methemoglobin reductase enzyme was diagnosed based on a specific assa y.