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HBA2

Synonyms
ECYT7, HBA-T2, HBH
External resources
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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