Common variable immunodeficiency: diagnosis by absent ABO reverse type.

Many causes for ABO discrepancy between red blood cell and serum testing have been cited in the literature. ABO discrepancy due to weak or absent reverse type is most often seen at the extremes of age. We report a case of ABO discrepancy in a 25-year-old woman who presented for wisdom teeth extraction. Initial serologic workup revealed total absence of isohemagglutinin anti-B in this group A, D+ individual. Further evaluation revealed decreased levels of all classes of immunoglobulins and a medical history significant for multiple episodes of infection. Based on the patient's history and laboratory data, she was diagnosed with common variable immunodeficiency (CVID). CVID can cause ABO discrepancy in an adult patient because of an absent ABO reverse type.