Naturally occurring clinically significant anti-M alloantibodies with wide thermal range: A series of three cases

Anti-M antibodies are usually of the immunoglobulin (Ig)-M type and have a cold thermal range, which is generally considered clinically insignificant. However, in some cases, there may also be an IgG component present exclusively. In addition to the discrepancy in blood grouping (attributable to the IgM component), the presence of an IgG component reacting at 37°C can interfere with pretransfusion testing, making it difficult to find fully compatible blood within a short time. In this report, we discuss three children: two boys aged five and 1½ years, respectively, and a female toddler aged 1 year who were all successfully treated using M-antigen negative packed red blood cells along with the standard treatment plan of the hospital. This was made possible by an established institutional blood donor registry comprising O-typed blood donors (n = 374), who were phenotyped for 21 erythrocyte antigens using commercially available monoclonal antisera (Ortho Clinical Diagnostics, Pvt Ltd., Mumbai, India).