digenic alpha thalassemia spectrum HBA1; HBA2-related digenic alpha thalassemia spectrum https://github.com/monarch-initiative/mondo/issues/7561 MONDO:0100564 GARD:0026283 alpha-thalassemia trait Mild microcytic anemia caused by variation in two of the four copies of the alpha hemoglobin genes, which can be in cis (e.g., large deletion of HBA1 and HBA2 genes) or in trans (e.g., HBA1 variant on one chromosome and HBA2 variant on the other chromosome).