Acute lymphoblastic leukemia (ALL) holds the leading position among oncohematological and oncological diseases found in children. Modern methods of treatment of acute leukemia have led to the increased life expectancy and its relapse-free prolongation, however, the problem as such, is far from a conclusive solution. ALL is accompanied by the development of numerous complications on the background of both disease and therapy. The analysis of clinical history revealed that Herpesvirus infections could serve as a risk factor for acute leukemia. The results of the analysis of the causes of complications and fatal outcomes show that the infectious complications play the leading role among the complications and mortality causes in children with acute lymphoblastic leukemia. The predominant etiological factors of the infectious processes in children with ALL are species of opportunistic pathogens. In the course of the investigation there was developed a diagnostic-prognostic “Pediatric severity scale of hematological patients”, which fully reflects the clinical condition of a patient and is able to predict the adverse effects of leukemia. It has been statistically established that the increase in the severity assessment of a patient with the manifestation of leukemia higher than 9 points, suggests the onset of lethal outcome. The assessment of the patient's condition above 11 points during induction therapy involves the onset of lethal outcome. The content of weight-average molecules (WAM) in the serum was significantly increased in children with ALL. Thus, WAM indicate the development of endogenous intoxication syndrome. The results of the research proved that endothelial dysfunction accompanies the course of ALL in children both before and after treatment. The average level of nitric oxide metabolites, nitrate content (NO₃) and the rate of vasodilation of the brachial artery decreases, while the nitrite content (NO₂) and the thickness index of IMC of the common carotid artery increases on the background of ALL. The presence of correlations between clinical, biochemical and immunological parameters allows the use of endothelial dysfunction markers as the signs of acceleration and the adverse course of ALL in children. A sum of NO₂+NO₃ lower than 32,99 μmol/l, leads to lethal outcomes. The content of NO₂ lower than 12,31 μmol/l, involves lethal outcomes. The increase of total NO2 content in the serum higher than 19,68 μmol/l forecasts, indicates the development of toxic hepatitis. The retention of signs of endothelial dysfunction in patients with leukemia in remission poses a risk of development of the diseases of the cardiovascular system and dictates the need for dispensary supervision of these patients in the follow-up. Acute lymphoblastic leukemia in children is manifested by deep depression of the humoral and cellular elements of the immune system. Significant deviations of Z-estimates of the content of CD3, CD4, CD8, CD16, B-lymphocytes and immunoglobulins have been statistically proved, as well as the increase in number circulating immune complexes at manifestation of the disease and further. It has been identified that the development of toxic hepatitis contributes to the suppression of both cellular and phagocytic links of immune systems in children with ALL. An association between gastrointestinal complications and the level of myeloperoxidase and circulating immune complexes has also been detected. The present research confirmed the significant contribution of HSP 70 in the development of oncohematological diseases. A significant increase in the content of HSP 70 in the serum of children with ALL has been recorded. Induction therapy has been shown to reduce the serum levels of HSP 70 in children with ALL. However, with that they do not normalize and remain significantly higher than the results of the control group. The correlation analysis showed a probable connection of HSP 70 with the degree of activity of the cancer process and the suppression of the immune system. The increasing tendency of the content of HSP 70 among patients with a fatal outcome has been identified. Thus, the scientific data on the significant contribution of HSP 70 in the development of ALL was supplemented. Statistical analysis in the search of possible markers of prognostic value and the development of infectious complications of ALL in children allows to single out the indicators of neutrophils’ content, as well as the level of nitric oxide metabolites and the total score within the “Pediatric scale for assessing the severity of hematological patients” as prognostic-significant. Focusing on these indicators and their probable correction can reduce the proportion of infectious complications of ALL in children.
