To evaluate the sleep quality and fatigue levels in children with familial Mediterranean fever (FMF) in comparison to healthy children. The Pediatric Quality of Life Multidimensional Fatigue Scale (PedsQL-MFS) and the Pittsburgh Sleep Quality Index (PSQI) were the instruments utilized to assess fatigue and sleep quality in children with FMF and controls, respectively. Spearman’s rank coefficient was decisive in determining the association between patient-reported outcome measures and disease-related features. Two hundred twenty-five (59.3% female) patients and 182 (51.6% female) healthy counterparts were enrolled in the study. In PSQI, where high scores indicate sleep disturbance, the median score was significantly higher in the patient group (5; 3–6) than the control group (3; 2–4) (p < 0.001). PEDsQL-MFS demonstrated significantly lower fatigue levels in the control group than patients (p = 0.01). The level of fatigue in the patient group was found to increase in correlation with sleep problems (r: − 0.750, p < 0.001). Additionally, a high correlation was present between the PSQI/PedsQL-MFS scores and the number of attacks in the last year (r: − 0.645, p < 0.001/r: 0.721, p < 0.001, respectively). There was no difference in terms of fatigue and sleep disorders between mutations (homozygous, heterozygous, or compound heterozygous) in the MEFV gene (p > 0.05).    Conclusion: High disease activity has a significant negative impact on the sleep quality and fatigue levels of patients with FMF. This study emphasizes the importance of assessing fatigue and sleep quality with objective outcome tools periodically in FMF patients throughout the disease course. What is Known:• Fatigue is a common matter that often accompanies rheumatic diseases and causes disability.• Chronic rheumatic diseases often experience poor sleep quality. What is New:• In high correlation with the disease severity of familial Mediterranean fever, sleep quality decreases and fatigue level increases significantly.• In familial Mediterranean fever patients, a negative correlation is present between age and the general fatigue and sleep/rest related fatigue scores (low scores indicating greater fatigue) and sleep quality is poorer in the adolescent age group.

Objective: Rheumatoid factor (RF)-positive polyarthritis is the least common type of juvenile idiopathic arthritis (JIA). Functional disability in RF-positive polyarthritis patients is much more severe than in patients with other subtypes; but data on this subtype alone is limited. This study aimed to analyze clinical features, long-term follow-up, treatment response, and remission status in a large multicenter cohort of RF-positive polyarthritis patients. Methods: This retrospective study included RF-positive polyarthritis patients that were followed up for ≥ 6 months between 2017 and 2022 by the Pediatric Rheumatology Academy (PeRA)-Research Group (RG). Data on patient demographics, clinical and laboratory characteristics were obtained from medical charts. JIA treatments and duration of treatment were also recorded. The patients were divided into 2 groups based on methotrexate (MTX) response, as follows: group 1: MTX responsive, group 2: MTX unresponsive. Clinical and laboratory findings were compared between the 2 groups. Results: The study included 56 (45 female and 11 male) patients. The median age at onset of RF-positive polyarthritis was 13.2 years [(interquartile range) (IQR): 9.0–15.0 years] and the median duration of follow-up was 41.5 months (IQR: 19.5–75.7 months). Symmetrical arthritis affecting the metacarpophalangeal and proximal interphalangeal joints of the hands was commonly observed. Subcutaneous MTX was the preferred initial treatment; however, it was ineffective in 39 (69.6%) of the patients. Of 25 patients followed for 24 months, 56% still had active disease at 24 months. Conclusion: During 2 years of treatment, 44% of RF-positive polyarthritis patients have inactive disease, and they should be considered as a distinct and important clinical entity requiring aggressive and early treatment.