Recurrent fever syndromes are autoinflammatory diseases. In their pathogenesis, no autoantibodies or autoreactive T-lymphocytes are found. Innate immunity and adaptive immunity are of great importance in this case. In the mid-latitudes, the most common syndrome is periodic fever with aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA), which mainly affects children under 5 years of age. Fevers occur cyclically, on average every 26–36 days. Characteristic features of PFAPA include the absence of any symptoms between fever episodes and undisturbed growth and development of the child. In laboratory tests, during a fever episode, elevated white blood cell count and an increase in inflammatory markers are observed. The recommended treatment is the use of glucocorticoids. In some cases, the use of colchicine or even an interleukin-1 receptor antagonist (anakinra) may be considered. The aim of this paper is to present the case of a 3.5-year-old boy hospitalised in the Department of Paediatrics, Nephrology and Paediatric Allergology of the Military Institute of Medicine due to recurrent episodes of fever with enlarged lymph nodes, occurring at regular intervals, as well as to draw attention to the difficulties encountered during the diagnosis of recurrent febrile episodes.

fever of unclear origin, recurrent fever syndromes, autoinflammatory diseases, lymphadenopathy, pharyngitis, aphthae