The HBA2 (Hemoglobin, alpha 2) gene represents the alpha globin chain of hemoglobin. Deletions in HBA2 are associated with alpha-thalassemia, a blood disorder where abnormal hemoglobin production can lead to anemia, bone problems and stunted growth. Thalassemia syndromes are classified by which and how many of the alpha and beta globins are missing. HBA2 may also be useful for subtyping breast cancers in immunohistochemistry; it has been found to be overexpressed in HER2+, ER-/PR- tumors and downregulated in triple-negative (ER-/PR-/HER2-) tumors. Immunohistochemistry of HBA2 in normal tissue shows positivity in erythrocytes and bone marrow. References: Scientific Reports. 2016. 6 (35773): 35773, DOI: 10.1038/srep35773