目的 探讨磁共振成像（MRI）对临床初诊为幼年特发性关节炎（JIA）的急性淋巴细胞白血病（ALL）患儿的诊断价值。方法 回顾性分析2018年1月—2020年12月以下肢疼痛为首发症状且临床初诊为JIA,但最终经骨髓检查确诊为ALL患儿（病例组）的临床资料。将同时期确诊的JIA患儿作为对照组。所有患儿均在就诊初期（未进行相关治疗前）行双膝关节MRI扫描,探讨MRI对儿童ALL与JIA的鉴别诊断价值。结果 病例组15例,男9例、女6例,中位年龄年龄5.1（3.6~7.8）岁,下肢关节疼痛病程25.0（16.5 ~35.5）天;对照组18例,男7例、女11例,中位年龄5.3（3.5~7.3）岁,下肢关节疼痛病程23.5（15.0~39.0）天。病例组中,13例患儿MRI可见双膝关节骨髓信号异常,多表现为弥漫性均匀或不均匀T1WI等低信号、T2WI高信号;2例MRI未见异常。对照组中,14例患儿MRI可见干骺端及骨骺信号异常,呈小斑片状T1WI等低信号、T2 WI高信号;4例MRI未见明显异常。以MRI特征中双膝关节病变弥漫分布为诊断标准,其诊断ALL的灵敏度和特异度为80.00%和94.44%;以T1WI等低信号及T2WI高信号为诊断标准,其灵敏度和特异度为86.67%和66.67%。病例组膝关节表观弥散系数（ADC）值低于对照组,差异有统计学意义（P<0.01）。ROC曲线分析显示,当ADC以0.88×10^-3 mm² /s为诊断阈值时,其诊断ALL的曲线下面积（AUC）为0.895,灵敏度为 86.7%,特异度为 83.3%,诊断准确率为 84.9%。结论 MRI作为一种无创的检查方法,对于以下肢疼痛为首发症状且实验室外周血检查无明显异常的ALL与JIA患儿的鉴别诊断具有较大临床价值。

Objective The aim of this study is to assess the diagnostic value of magnetic resonance imaging (MRI) in children with acute lymphoblastic leukemia (ALL) misdiagnosed as juvenile idiopathic arthritis (JIA). Methods Retrospective analysis was performed on children with lower extremity pains as the first symptom in our hospital from January 2018 to December 2020 who were initially diagnosed as JIA. Among them, fifteen patients were finally diagnosed as ALL confirmed by bone marrow aspiration, eighteen patients were JIA. All of them underwent blood routine and bilateral knee MRI examination before any treatment. The MRI were performed, including T1WI, spectral attenuated inversion recovery (SPAIR) T2WI and DWI (b value was 0 and 600 s/mm²). The MRI features of bone marrow were assessed by extent and location, the signal intensity, morphological features. The ADC value of all knee joints were measured and were compared between the two groups. The diagnostic value was calculated. Results There were no statistically significant differences in WBC count, hemoglobin (Hb), platelet count (PLT), C- creative protein (CRP) and erythrocyte sedimentation rate (ESR) between the case group and the control group (P>0.05). Abnormal signal intensity of bone marrow in bilateral bones of lower extremities was demonstrated in 13 patients with ALL patients which showed diffuse homogeneous iso- or low-signal intensity on T1W images and high signal intensity on T2 SPAIR images; other 2 patients had normal results of MRI. In 18 patients with JIA, 14 patients showed ill-defined patchy areas in the metaphysis and epiphysis with iso- or low-signal intensity on T1W images and high signal intensity on T2 SPAIR images; other 4 cases of JIA patients had normal results of MRI. The positive rate in the case group was higher than that in the control group. Compared with the control group, the MRI features of the case group were bilateral diffuse low signal intensity in T1W images and high signal intensity in T2W images (P<0.01). The ADC values in ALL group were lower than control group (t=-14.133, P<0.01). Taking 0.88×10^-3 mm² /s as the threshold, AUC of ROC curve in diagnosis of ALL was 0.895, with sensitivity, specificity and diagnostic accuracy was 86.7%, 83.3% and 84.9%. Conclusion MRI may serve as a noninvasive method to help discrimination of ALL from JIA in children presenting with lower extremity pains. MRI show diffuse abnormal signal intensity on bilateral lower extremities are more likely to be initial ALL.