RESUMEN
Naturally occurring anti-Kpa antibody is extremely rare and was first reported in 1957, named after the first producer 'Penney'. However, the subsequent anti-Kpa reports presented were all anti-Kpa due to isoimmunization. Individuals with severe bacterial infections particularly Gram-negative bacteria are known to be capable of producing cross-reactive antibodies against Kell blood group system. However, such uncommon antibodies like anti-Kpa can be easily missed in routine pre-transfusion testing unless the panel cells containing low incidence antigen are used for antibody screening. Here, we report a case of naturally occurring anti-Kpa antibody, identified incidentally during pre-transfusion testing of a 12-month-old female infant with the diagnosis of Niemann-Pick disease and recurrent bacterial (Escherichia coli) infection.