Background. Children with juvenile idiopathic arthritis (JIA) represent a special cohort of patients with chronic somatic pathology, characterized by severe damage to the musculoskeletal system and other vital organs and systems, which is associated with immune and metabolic changes in the body. Data regarding the provision of vitamin D (VD) in patients with JIA and the significance of its deficiency in the initiation, activation of the autoimmune process, the prognosis of the course of the disease, the risk of developing complications and the effectiveness of protocol therapy are contradictory. Objective. To investigate the body's supply of vitamin D in patients with juvenile idiopathic arthritis with the determination of the trigger factors of its deficiency, the assessment of the immune status and changes in the nucleotide sequence in the genes of innate immunity. Materials and methods. Research was conducted during 2016-2021 at the Institute in 119 patients with JIA aged 6 to 12 years. The concentration of 25OHD was determined in blood serum using commercial Vitamin D3 kits (Screeningkit, Switzerland). Immunological studies were performed by flow cytofluorimetry and enzyme immunoassay. For panel sequencing of 407 genes regulating immune functions, high-throughput panel exome sequencing was used on Illumina's HiSeq machine (made in the USA) at the Invitae laboratory (USA). The obtained digital data were processed by methods of statistical analysis using the Microsoft Excel computer package. Results. A high frequency of low supply of vitamin D in patients with JIA was revealed: vitamin D insufficiency was diagnosed in 96 (80.6 %), and its deficiency - in 38 (31.9 %) children. The lowest levels of 25ОНD concentration in blood serum (less than 15 ng/ml) are observed in patients with stage II–III disease activity, especially at the beginning of the pathological process. Vitamin D deficiency (DVD) was associated with the activity and severity of the clinical course, frequent exacerbation of the joint syndrome, the expressiveness of changes in the humoral and cellular immunity of patients. The main risk factors for reducing the body's supply of WD in patients with JIA have been determined, which must be taken into account during their observation and treatment. High activity of JIA in patients with VD deficiency in the body was associated with a significant increase in the number of CD3+ T-cells, CD3+CD4+ helper-inducer T-cells, activated HLA-DR+/CD3+ T-cells, ESR, C-reactive protein concentration (CRP), tumor necrosis factor (TNF), circulating immune complexes (CIC), immunoglobulins, which allows considering DWD as a likely predictor of severe and prognostically unfavorable course of rheumatic disease. Nucleotide sequence changes in the NOD2 gene were detected in 18.1 % of patients with JIA: c.2104C>T (p.Arg702Trp), c.3019dupC (p.Leu1007Profs*2). The of variable changes in patients with JIA is statistically significantly different from the population [VSh = 11.39; 95 % CI (2.39-54.22)]. DVD was detected in all children with mutations in the NOD2 gene – (17.2 ± 3.29) ng/ml, and in children without changes in the nucleotide sequence - in 23 (85.1 %) children [SS = 0.097; DI (0.03-0.31)], the concentration of VD is significantly higher - [(26.68 ± 2.34) ng/ml, p = 0.026]. Conclusions. The conducted studies confirm the presence of a decrease in the body's supply of vitamin D in patients with JIA, which is associated with a high activity of the pathological process and pronounced immunological changes in the body, which allows us to consider its deficiency as a likely predictor of a severe and prognostically unfavorable course of the disease. It has been proven that the concentration of vitamin D in JIA is higher in patients without changes in the nucleotide sequence in the NOD2 gene, which must be taken into account when predicting and evaluating the body's response to the treatment of juvenile arthritis. Key words: juvenile idiopathic arthritis, vitamin D, immunological status, genetic sequencing, children.

Background. In the pathogenesis of juvenile idiopathic arthritis (JIA), the main role is played by immunopathological changes in the body with a loss of tolerance to the elements of own tissues; herewith, disorders of calcium and bone metabolism are very important. Such changes occur as a result of autoimmune inflammation, pharmacotherapy, and the influence of a number of other factors that negatively affect calcium homeostasis in the body. Purpose: to study the features of calcium homeostasis and certain aspects of its disorders with an assessment of the structural and functional state of bone tissue, taking into account clinical subtypes and disease activity. Material and methods. Sixty-two children with JIA aged 3.5 to 16 years were examined, of them 11 had systemic and 51 had oligo- and polyarthritis. There were determined serum concentrations of a total calcium using the Lachema test kit (Czech Republic), protein-bound and ultrafiltered fractions, content of inorganic phosphorus (with the generally accepted spectrophotometric method using the Cobas 6000 analyzer and test systems by Roche Diagnostics, Switzerland), the activity of total alkaline phosphatase and its isoenzymes (bone and intestinal) using the Lachema test system (Czech Republic). Ultrasonic osteometry of the calcaneal (trabecular) bone was performed on the Achilles device (Lunar, USA). Results. A significant decrease was found in the average concentration of total calcium, protein-bound calcium in systemic JIA and in high disease activity. The concentration of the ultrafiltered calcium fraction decreased only with high disease activity. The average concentration of inorganic phosphorus in children with oligo- and polyarthritis was within the normal range, while in systemic JIA it decreased. A significant decrease in the serum content of inorganic phosphorus, as well as in the activity of total alkaline phosphatase and its bone isoenzyme was detected in patients with high activity of systemic JIA. In patients with JIA (oligo-, polyarthritis) characterized by a slowly progressive rheumatic process, only the indicator of broadband ultrasound attenuation significantly changed during the first year of the disease, while the speed of ultrasound propagation and the index of bone tissue strength were not changed. In patients with a longer duration of the disease, all densitometric indicators decreased significantly. In the group of patients with systemic JIA and a rapidly progressive course, high activity of the disease that required a glucocorticoid therapy, a significant loss of bone mass was noted by the end of the first year of the disease. Conclusions. In JIA, there are changes in the concentration of total calcium and its protein-bound and ultrafiltered fractions in the blood serum, which indicate the tension of calcium-phosphorus metabolism and possible calcium deficiency in the body already at the early stages of the pathological process. A decrease in the activity of the alkaline phosphatase and its bone isoenzyme is associated with a violation of the structural and functional changes in the bone system of patients with JIA, which progresses with the duration of the disease. Patients with JIA require timely diagnosis and monitoring of calcium-phosphorus metabolism disorders with an assessment of the structural and functional state of the bone system for purposeful correction of comprehensive therapy due to the use of drugs in order to increase bone tissue regeneration, reduce the progression of osteopenia and osteoporosis, and preserve the health of the growing organism.

Purpose - to increase the effectiveness of prevention and correction of D hypovitaminosis in juvenile idiopathic arthritis (JIA) by optimizing the algorithms of dosage regimens and duration of vitamin D supplementation. Materials and methods. A clinical and laboratory examination of 118 children aged 3 to 18 years with a diagnosis of JIA was carried out. Vitamin D status was assessed by the concentration of 25(OH)D in the blood serum using a Reader ER 500 enzyme immunoassay photoelectric analyzer. All patients in the complex of therapeutic measures were prescribed vitamin D3 preparations according to the developed algorithms, taking into account the presence of trigger factors for reducing the supply of this vitamin to the body, existing world recommendations and the initial level of 25(OH)D in blood serum. Results. The use of vitamin D3 preparations according to the scheme of 4000 IU/d for two months, followed by continuation at a dose of 2000 IU/d for one month, contributed to the achievement of sufficient concentrations of 25(ОH)D (36.7-47.5 ng/ml) in the blood serum in all patients. When taking vitamin D at a dose of 4000 IU/d for one month, and then for another two months at 2000 IU/d, the optimal concentrations of 25(OH)D in the blood serum (31.55-45.14 ng/ml) were achieved only in 52.9% children. Maintenance therapy in the future for 6 months at a dose of 1000 IU/d provided sufficient concentrations of vitamin D in 61.86% of children, and in 38.14% there was a tendency to reduce the content of 25(OH)D (26.83±2.99) ng/ml, which indicated the insufficiency of the specified maintenance dose of vitamin D for children with chronic progressive inflammation and the presence of comorbid pathology and the impact on adverse risk factors that affect the body’s supply of this vitamin. Conclusions. In JIA, the dose of saturation (4000-6000 IU/d) with vitamin D preparations should be determined depending on the initial degree of its insufficiency in the body, the characteristics of the clinical course and treatment of the underlying disease, and the presence of factors that contribute to a decrease in the supply of vitamin D to the body. Maintenance therapy at a dose of 2000 IU/d for 6 months makes it possible to maintain the optimal concentration of 25(OH)D in the body with a high probability. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.

Castleman’s disease (angiofollicular lymphoma, giant lymph node hyperplasia, Castleman’s pseudotumor) is an understudied orphan lymphoproliferative disease with a long period of asymptomatic course and a high risk of malignancy, and variability of its clinical features can cause difficulties in diagnosis. The aim of the study. To acquaint clinicians and increase the effectiveness of early diagnosis and treatment of Castleman’s disease (CD) in children to prevent malignancy and improve prognosis. Results. The article presents a clinical case of CD in a 3.5-year-old boy with a long history of fever, stunted growth, sweating, arthralgia, anemia, high laboratory inflammatory factors, elevated IL-6. There was a complex diagnostic search except for infectious, immunodeficiency, autoimmune conditions. The diagnosis of hyaline-vascular type of CD was confirmed by immunohistochemical examination after lymph node excisional biopsy. Rapid positive dynamics was noted after radical removal of the lymph node conglomerate. At follow-up after 8 months, the patient met criteria for clinical and laboratory remission. Conclusions. Castleman’s disease should be included in the search algorithm for lymphoproliferative diseases. Determining the role of genetic mutations in interferon regulatory factor (IRF8) is of scientific interest to clarify the etiology of this disease.