- Imbalanced hemoglobin synthesis (HP:0005560, a Human Phenotype Ontology term): Normal hemoglobin synthesis is characterized by production of equal amounts of alpha and beta globins. This term refers to a deviation from this pattern and is the main characteristic of the various forms of thalassemia. Evidence: TAS. Frequency: Very frequent (HP:0040281, a Human Phenotype Ontology term). (ORPHA:90039)
- Abnormal hemoglobin (HP:0011902, a Human Phenotype Ontology term): Anomaly in the level or the function of hemoglobin, the oxygen-carrying protein of erythrocytes. Evidence: TAS. Frequency: Very frequent (HP:0040281, a Human Phenotype Ontology term). (ORPHA:90039)
- Reduced hemoglobin A (HP:0011905, a Human Phenotype Ontology term): Hemoglobin A (HbA) contains two globin alpha chains and two globin beta chains. HbA is normally the main adult hemoglobin, representing about 96-98 percent of all hemoglobin. This term represents a decreased in the proportion of HbA below this limit, and can be seen in various forms of thalassemia. Evidence: TAS. Frequency: Frequent (HP:0040282, a Human Phenotype Ontology term). (ORPHA:90039)
- Reduced beta/alpha synthesis ratio (HP:0011906, a Human Phenotype Ontology term): A reduction in the ratio of production of beta globin to that of alpha globin. This is the major abnormality in the various forms of beta thalassemia. Evidence: TAS. Frequency: Frequent (HP:0040282, a Human Phenotype Ontology term). (ORPHA:90039)
- Reduced alpha/beta synthesis ratio (HP:0011907, a Human Phenotype Ontology term): A reduction in the ratio of production of alpha globin to that of beta globin. This is the major abnormality in the various forms of alpha thalassemia. Evidence: TAS. Frequency: Frequent (HP:0040282, a Human Phenotype Ontology term). (ORPHA:90039)
- Decreased mean corpuscular volume (HP:0025066, a Human Phenotype Ontology term): A reduction from normal of the mean corpuscular volume, or mean cell volume (MCV) of red blood cells (usually defined as an MCV below 80 femtoliters). Evidence: TAS. Frequency: Frequent (HP:0040282, a Human Phenotype Ontology term). (ORPHA:90039)
- Decreased mean corpuscular hemoglobin concentration (HP:0025547, a Human Phenotype Ontology term): A reduction from the normal range of the average amount of hemoglobin per red blood cell (27 to 31 picograms/cell). A reduced mean corpuscular hemoglobin (MCH) may indicate a hypochromic anemia, but the MCH may be normal if both the total hemoglobin and the red blood cell count are reduced. Evidence: TAS. Frequency: Frequent (HP:0040282, a Human Phenotype Ontology term). (ORPHA:90039)
- Increased HbA2 hemoglobin (HP:0045048, a Human Phenotype Ontology term): An elevated concentration in the blood of hemoglobin A2 (HbA2), which is a normal variant of hemoglobin A that consists of two alpha and two delta chains and is normally present at low levels in adults but may be increased in beta thalassemia. Evidence: TAS. Frequency: Frequent (HP:0040282, a Human Phenotype Ontology term). (ORPHA:90039)
- Sickled erythrocytes (HP:0030058, a Human Phenotype Ontology term): An irreversible distortion of the morphology of an erythrocyte such that the cells are elongated and curved, resembling the blade of a sickle (the hand-held agricultural tool traditionally used to harvest grains). Evidence: TAS. Frequency: Occasional (HP:0040283, a Human Phenotype Ontology term). (ORPHA:90039)
- HbS hemoglobin (HP:0045047, a Human Phenotype Ontology term): Presence of an abnormal type of hemoglobin characterized by the substitution of a glutamic acid residue at position 7 following the initial methionine residue by a valine (the mutation causative of sickle cell disease). The mutation promotes the polymerization of the HbS under conditions of low oxygen concentration. HbS can be identified by multiple methodologies including hemoglobin electrophoresis and high-performance liquid chromatography. Evidence: TAS. Frequency: Occasional (HP:0040283, a Human Phenotype Ontology term). (ORPHA:90039)
- Pallor (HP:0000980, a Human Phenotype Ontology term): Abnormally pale skin. Evidence: TAS. Frequency: Very rare (HP:0040284, a Human Phenotype Ontology term). (ORPHA:90039)
- Splenomegaly (HP:0001744, a Human Phenotype Ontology term): Abnormal increased size of the spleen. Evidence: TAS. Frequency: Very rare (HP:0040284, a Human Phenotype Ontology term). (ORPHA:90039)
- Anemia (HP:0001903, a Human Phenotype Ontology term): A reduction in erythrocytes volume or hemoglobin concentration. Evidence: TAS. Frequency: Very rare (HP:0040284, a Human Phenotype Ontology term). (ORPHA:90039)
- Abdominal pain (HP:0002027, a Human Phenotype Ontology term): An unpleasant sensation characterized by physical discomfort (such as pricking, throbbing, or aching) and perceived to originate in the abdomen. Evidence: TAS. Frequency: Very rare (HP:0040284, a Human Phenotype Ontology term). (ORPHA:90039)
These phenotypes are associated with the disease Hemoglobin D disease (ORPHA:90039, an Orphanet rare-disease identifier).