Very rare. Autosomal dominant transmission. Hemoglobin Miwate is responsible for congenital methemoglobinemia (see this term). It is due to the substitution of histidine by tyrosine in position 87 on the hemoglobin α chain. This substitution causes a modification in the absorbance of light and so an error of saturation measurement by pulse oximetry. In addition, oxygenated and deoxygenated forms of this hemoglobin have an identical absorption spectrum, different from that of HbA and methemoglobin A.

This hemoglobin  has also a lower affinity for O2: at paO2 of 100 mmHg, hemoglobin is only 60% saturated.

Anesthetic implications:

cyanosis; pulse oxymetry is useless (as well as transcutaneous cooximetry i.e. Radical 7®); rely on arterial blood gases and/or transcutaneous paO2

References :

-        Kuji A, Satoh Y, Kikuchi K, Satoh K, Joh S.
The anesthetic management of a patient with haemoglobin Miwate.
Anesth Analg 2001; 93: 1192-3

-        Mathew PJ, Gupta A, Natarajan V, Ganesan R, Sharma R.
Failure of pulse oximetry and cooximetry as monitors in a patient with hemoglobin Miwate: a case report.
A&A Practice 2018 ; 10 : 293-5.

Updated: June 2018