BACKGROUND Felty's syndrome (FS) is characterized by the triad of rheumatoid arthritis (RA), splenomegaly and neutropenia. The arthritis is typically severe and virtually always associated with high-titer rheumatoid factor. The presence of persistent neutropenia is generally required to make the diagnosis. Most patients diagnosed with FS are aged 50-70 years and have had RA for more than 10 years. It is rarely seen in patients with juvenile idiopathic arthritis (JIA), with only five cases having been reported throughout the world. CASE PRESENTATION The present study describes the case of a 14-year-old female with a seven-year history of polyarticular JIA, presenting with splenomegaly, hepatomegaly, cholestasis and thrombocytopenia. However, she occasionally developed neutropenia. Titers of rheumatoid factor and anti-CCP were persistently high, and the antinuclear antibody titer was 1:320, while the antibody results for anti-dsDNA and anti-Sm were negative. Serum levels of IgA, IgG, IgM and IgE were all persistently elevated, and the ratio of CD19+ lymphocytes in the subgroups of lymphocytes was persistently high. The level of complements was normal. No STAT3 and STAT5B mutations were found by next-generation sequencing. The patient did not respond to methotrexate, prednisolone, hydroxychloroquine (HCQ), sulfasalazine and etanercept but was responsive to rituximab. CONCLUSIONS JIA, thrombocytopenia and splenomegaly are the most common and important features in six children with FS, while persistent neutropenia is not seen in all these patients. No complement deficiency has been found in children with FS so far. Manifestations of FS without neutropenia may be extremely rare. There are differences between adults and children in the clinical and laboratory features of FS.

中文翻译：

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Felty's综合征患儿的表型变异：病例报告。

背景技术Felty综合征（FS）的特征是类风湿关节炎（RA），脾肿大和中性粒细胞减少症的三联征。关节炎通常是严重的，并且实际上总是与高滴度类风湿因子有关。通常需要持续存在中性粒细胞减少来进行诊断。大多数被确诊为FS的患者年龄在50-70岁之间，患有RA超过10年。在青少年特发性关节炎（JIA）患者中很少见到这种情况，全世界仅报道了五例。病例介绍本研究描述了一名14岁女性，患有多关节JIA病史7年，伴有脾肿大，肝肿大，胆汁淤积和血小板减少症。但是，她偶尔会出现中性粒细胞减少症。类风湿因子和抗CCP抗体滴度持续偏高，抗核抗体效价为1：320，抗dsDNA和抗Sm抗体结果均为阴性。血清中IgA，IgG，IgM和IgE均持续升高，并且淋巴细胞亚群中CD19 +淋巴细胞的比例持续升高。补体水平正常。下一代测序未发现STAT3和STAT5B突变。该患者对甲氨蝶呤，泼尼松龙，羟氯喹（HCQ），柳氮磺吡啶和依那西普没有反应，但对利妥昔单抗有反应。结论JIA，血小板减少和脾肿大是6例FS儿童的最常见和重要特征，而在所有这些患者中均未发现持续性中性粒细胞减少。迄今为止，在FS儿童中未发现补体缺乏症。没有中性粒细胞减少症的FS表现可能非常罕见。