Objective:To explore the diagnostic value of the macrophage activation syndrome/systemic juvenile idiopathic arthritis（MS）score in macrophage activation syndrome（MAS）associated with systemic juvenile idiopathic arthritis（sJIA），and to provide a reference for clinical work.Methods:This study was a retrospective case-control analysis，conducted on the patients initially diagnosed as sJIA-associated with MAS and admitted into the Department of Rheumatology and Immunology of Children's Hospital Affiliated to Xi 'an Jiaotong University from July 1st，2016 to June 30th，2023. All of the patients met the diagnostic criteria for patients with MAS associated with sJIA according to the 2016 European Alliance of Associations for Rheumatology（EULAR）/American College of Rheumatology（ACR）/Pediatric Rheumatology International Trials Organization（PRINTO）standards. The basic information at baseline，clinical manifestations，and auxiliary examination results were collected. The MS score was applied to re-evaluate the children diagnosed as sJIA-associated with MAS. When the MS score ≥-2.1，the possibility of sJIA with MAS was high. Thirty cases of sJIA without MAS were randomly selected as the control group.Results:There were 28 cases in the MAS group，including 13 males（46.43%）and 15 females（53.57%），with an average age of（7.51±4.01）years. Compared with the control group，the MAS group were significantly more likely to have high fever（ χ2=8.539， P=0.003），hepatomegaly（ χ2=11.621， P<0.001），splenomegaly（ χ2=11.710， P<0.001）and neurological involvement（ χ2=27.619， P<0.001），with the differences being statistically significant. Meanwhile，there were statistically significant differences between the two groups in terms of white blood cell count（ Z=-4.001， P<0.001），neutrophil count（ Z=-3.659， P<0.001），platelet count（ Z=-4.687， P<0.001），albumin level（ Z=-4.018， P<0.001），alanine aminotransferase（ Z=-3.846， P<0.001），aspartate aminotransferase（ Z=-5.932， P<0.001），lactate dehydrogenase（ Z=-6.150， P<0.001），triglycerides（ Z=-5.874， P<0.001），fibrinogen（ Z=-5.808， P<0.001），ferritin（ Z=-5.280， P<0.001），erythrocyte sedimentation rate（ Z=-3.971， P<0.001），ferritin/erythrocyte sedimentation rate（ Z=-5.433， P<0.001），reduction of two-line cells in blood（ χ2=11.408， P<0.001）and the presence of hemophagocytosis in bone marrow smears（ χ2=28.260， P<0.001）. Moreover，there was a statistically significant difference in MS scores between the two groups（ Z=-6.148， P<0.001），with higher MS scores in the MAS group. Nevertheless，this study showed the median MS scores of both groups ≥-2.1. Conclusion:The MS score was significant to a certain degree as reference for the diagnosis of MAS，and this study showed that the MS score in the MAS group was significantly higher than the control group. However，the median MS scores in both groups were no less than -2.1. This might be related to the influence of factors during the assessment，which made it necessary to optimize the cutoff values of the MS score. Therefore，prospective studies should be carried out on the role of MS score in early identification of MAS.

To analyze a case of thin basement membrane nephropathy combined with juvenile idiopathic arthritis diagnosed in November 2017 in Children′s Hospital of Chongqing Medical University.A male patient with 7 years and 11 months old presented with swelling of bilateral interphalangeal joints and abnormal gait was diagnosed as juve-nile idiopathic arthritis.Urine examination revealed microscopic hematuria.Long-term follow-up after discharge showed recurrent joint symptoms and persistent microscopic hematuria.In February 2019, genetic testing showed the COL4A4 gene mutation (c.3479G>A p. G1160E). Through literature review, a case of rheumatoid arthritis complica-ted with Alport syndrome caused by the COL4A5 gene mutation c. 1351T>C (p.Cys451Arg) was previously reported.Both of 2 patients were diagnosed as collagen type Ⅳ-related renal diseases complicated with arthritis, and multiple joints involvement and renal involvement were detected.Excluding the influence of accidental factors and drugs, arthritis and some kidney diseases may have a co-pathogenesis under genetic background.The specific mechanism needs further exploration.This case report provided novel direction for the diagnosis and treatment of relevant diseases.