Background: Tuberculosis (TB) is infectious illness that poses a chronic threat to public health due to a variety of intricate biological and sociological factors. Examination of adenosine deaminase (ADA) allelic variations would give an idea about genetic predisposition toTB. ADA has been thoroughly investigated as a biochemical marker in pleural fluid.
Objectives: This work aimed to investigate the possible  association between ADA ene  polymorphism and the susceptibility to develop active TB disease and to evaluate the activity of ADA in these patients.
Patients and methods: A case-control study of 40 patients with active TB, in addition to 40 healthy,unrelatedvolunteers used as controls. Clinical and radiological evaluations and routine laboratory investigations were done on all participants. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used to identify the ADA G22A gene polymorphism. Measurement of ADA activity using a colorimetric assay kit.
Results: Among the included TB patients, 85% have pulmonary TB, and 60% have abnormal chest X-ray. There was significantly higher ADA activity in TB patients (38.40 ± 2.509 U/L) compared to controls (22.30 ± 5.355 U/L) (p < 0.001). There was a significantly higher frequency of the GA genotype and A allele of the ADA G22A gene polymorphism among patients compared to controls, p < 0.001 for all. Odds ratio (95% CI) for GA genotype = 2.188 (1.470-3.254), and for A allele = 2.188 (1.322-3.620) indicating a strong genetic  association between the GA genotype  and A allel and increased susceptibility to TB.
Conclusion: The GA genotpe and A allel of ADA G22A gene polymorphism was  strongly associated with increased risk of TB. ADA activity could be considerd as a biomarker for pulmonary TB.