Comorbid conditions are considered disorders (diseases) that are more common in a certain disease than in the general population and share some common etiological or pathogenetic mechanisms with it. Comorbidity increases the severity of the patient's condition and worsens the prognosis.  Systemic lupus erythematosus (SLE) is an autoimmune chronic disease of unknown etiology, in which various organs and systems are involved in the pathological process. Starting in childhood or young age, the disease gradually progresses and, with ineffective treatment, leads to loss of functional ability of patients and disability. It has been proven that patients with SLE develop a number of comorbid conditions over time, which are the consequences of complicated and iatrogenic comorbidity. The purpose of the study: to establish the presence of kidneys, lungs, and blood lipid spectrum comorbid conditions in children with systemic lupus erythematosus. 

Materials and methods of the study: 67 children with SLE aged 13.89 ± 0.39 years and disease duration 3.63 ± 0.41 years were examined. The following studies were conducted: to study lung function, spirometry was performed on the Spirolab III device (manufactured by Medical International Research, Italy) using the WinSpiroPRO 1.0 5.6.0 program; to study the lipid spectrum, a biochemical blood test was performed on the general-purpose automatic analyzer-photometer "CORMAY MULTI" (Poland) with determination of the level of total cholesterol (TC), triglycerides (TG), low-density lipoproteins (LDL) and atherogenic coefficient (CA); to determine kidney function, urine was examined according to the Zimnytsky method with measurement of urine density and daily protein intake, and a biochemical urine test with calculation of glomerular filtration rate (GFR). Statistical processing of the obtained data was carried out using parametric and nonparametric statistical methods using certified applied computer programs SPSS17 (license 4а180844250981ae3dae-s/nSPSS17).

Results: in the group of children with a disease duration of one to 3 years, proteinuria was registered in 68.1% of cases and in isolated cases - changes in GFR: a decrease in 4.4% and hyperfiltration - in 9.0%. In the group of children with a duration of the pathological process over 3 years, more profound changes in kidney function were detected. Thus, almost all patients had proteinuria (90.4%). The frequency of a decrease in GFR increased to 19.0%, and in 14.2% of cases a decrease in the concentration function of the kidneys was detected. When conducting spirometry, 37.5% of patients revealed a decrease in the function of external respiration of the first degree, mainly of the restrictive type. This was manifested (according to spirometry) by a decrease in the forced vital capacity of the lungs (FVC) (up to 80% of the FVC proper), while the forced expiratory volume in the first second (FEV1) and the Tiffno index (FEV1/FVC) remained within normal limits. An increase in the level of total cholesterol to (5.16 ± 0.25) mmol/l and LDL cholesterol to (2.85 ± 0.31) mmol/l was detected, which exceeded the permissible level and caused an increase in the CA to (2.21 ± 0.26). The maximum levels of proatherogenic fractions of the blood lipid spectrum were recorded in patients with high activity of SLE, and over time, against the background of treatment, their decrease to optimal values with the corresponding normalization of the CA occurred.  Thus, in children with a disease duration of more than 3 years, renal dysfunction occurs not only due to the glomerular (GFR), but also due to the tubular apparatus. From the side of the external respiratory function, mild respiratory disorders of the restrictive type are formed. With a high degree of activity of the inflammatory process, hyperlipidemia is formed, which may be an early factor in the development of atherosclerosis in children with SLE.