Uniprot Description A clonal disorder characterized by the polyagglutination of red blood cells by naturally occurring anti-Tn antibodies following exposure of the Tn antigen on the surface of erythrocytes. Only a subset of red cells express the antigen, which can also be expressed on platelets and leukocytes. This condition may occur in healthy individuals who manifest asymptomatic anemia, leukopenia, or thrombocytopenia. However, there is also an association between the Tn antigen and leukemia or myelodysplastic disorders.