Home > Gene Browser > HBA2
HBA2
- Synonyms
- ECYT7, HBA-T2, HBH
- External resources
- NCBI3040
- OMIM141850
- EnsemblENSG00000188536
- HGNCHGNC:4824
- Summary
- The human alpha globin gene cluster located on chromosome 16 spans about 30 kb and includes seven loci: 5'- zeta - pseudozeta - mu - pseudoalpha-1 - alpha-2 - alpha-1 - theta - 3'. The alpha-2 (HBA2) and alpha-1 (HBA1) coding sequences are identical. These genes differ slightly over the 5' untranslated regions and the introns, but they differ significantly over the 3' untranslated regions. Two alpha chains plus two beta chains constitute HbA, which in normal adult life comprises about 97% of the total hemoglobin; alpha chains combine with delta chains to constitute HbA-2, which with HbF (fetal hemoglobin) makes up the remaining 3% of adult hemoglobin. Alpha thalassemias result from deletions of each of the alpha genes as well as deletions of both HBA2 and HBA1; some nondeletion alpha thalassemias have also been reported.
Variant counts
The variants found in rare patients tested by 3billion are classified and counted according to ACMG guidelines. The variants with over 5% variant frequency in population genome databases ( gnomAD, dbSNP, etc) are excluded.
- Pathogenic
- 3
- Likely pathogenic
- 52
- VUS
- 490
- Likely benign
- 1,515
- Benign
- 0
Patient phenotypes
Proportions of phenotypes among 55 patients carrying pathogenic or likely pathogenic variants on HBA2 gene are displayed below.
- Phenotype class
- Patients in 3billion (%)
- Abnormality of the nervous system
- 40%
- Abnormality of the eye
- 29.1%
- Abnormality of the musculoskeletal system
- 29.1%
- Abnormality of the cardiovascular system
- 21.8%
- Abnormality of the digestive system
- 21.8%
- Abnormality of the integument
- 21.8%
- Abnormality of limbs
- 20%
- Abnormality of the genitourinary system
- 20%
- Abnormality of head or neck
- 16.4%
- Abnormality of the immune system
- 16.4%
- Growth abnormality
- 14.5%
- Abnormality of the endocrine system
- 12.7%
- Abnormality of blood and blood-forming tissues
- 7.3%
- Abnormality of the respiratory system
- 5.5%
- Constitutional symptom
- 5.5%
- Abnormality of prenatal development or birth
- 1.8%
- Abnormality of the ear
- 1.8%
- Neoplasm
- 1.8%
- Abnormal cellular phenotype
- 0%
- Abnormality of metabolism homeostasis
- 0%
- Abnormality of the breast
- 0%
- Abnormality of the thoracic cavity
- 0%
- Abnormality of the voice
- 0%
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