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.