Several host genes proven to contribute to ac­tive tuberculosis (TB) and some of the localized ma­jor susceptibility loci, which influence lung cancer (LC) risk, are of considerable scientific interest, but do not confer high enough risk to be clinically rel­evant. Assuming that these diseases are genetically controlled, we hypothesized that retreat from opti­mal homozygosity level, as well as a changed vari­ability among the patients, could be the population-genetic parameter for prediction of illness. We per­formed a homozygous-recessive-characters (HRCs) test based analysis of the presence, distribution and individual combination of 23 selected genetically-controlled morpho-physiological traits in groups of LC patients, patients with pulmonary TB and healthy control subjects. This study showed: i) a statistically significant difference of the middle values of genetic homozygosity between both patients groups and the control group, ii) differences in the type of distribu­tion, and iii) differences in the presence of certain individual combinations of such traits. The frequen­cy of blood group O was significantly decreased in the TB group compared to the general population.

According to their population-genetic structure, LC patients, TB patients and healthy controls represent three different groups. The retreat from optimal ho-mozygosity level towards decrease that we found in both LC and TB patients support the influence of a dominant factor in development of these diseases.

Key words: Genetic predisposition; Lung can­cer (LC); Tuberculosis (TB); Phenotype; Marker; Population genetic

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School of Medicine University of Belgrade, Bel­grade, Serbia

Clinical Centre of Serbia, Institute of Lung Diseases and Tuberculosis, Research and Epidemiology De­partment, Belgrade, Serbia Serbian Academy of Sciences and Arts, Belgrade, Serbia