Objetivo: Avaliar as características clínicas e laboratoriais para diferenciar leucemia linfoblástica aguda (LLA) da artrite idiopática juvenil forma sistêmica (AIJs) no início da doença. Métodos: Cinquenta e sete pacientes com LLA com envolvimento musculoesquelético, sem blastos no sangue periférico e sem terapia com glucocorticoide no início da doença e 102 pacientes com AIJs (critérios ILAR) foram retrospectivamente avaliados. Foram estudadas as seguintes características: febre, exantema reumatoide, artrite, dor em membros, hepatomegalia, esplenomegalia, pericardite, miocardite, pleurite, perda de peso, sangramento, anemia, leucopenia, neutropenia, plaquetopenia, níveis séricos elevados de velocidade de hemossedimentação (VHS) e de desidrogenase lática (DHL). Resultados: A mediana da idade de início da doença foi significativamente maior em pacientes com LLA comparada com AIJs (5,8 vs. 3,8 anos, p=0,0006). As frequências de dor em membros, hepatomegalia, perda de peso e manifestações hemorrágicas foram significativamente maiores em LLA versus AIJs (70% vs. 1%, p<0,0001; 54% vs. 32%, p=0,0075; 30% vs. 8%, p=0,0005; 98% vs. 0%, p=0,0053; respectivamente). Igualmente, as frequências de anemia, leucopenia, neutropenia, plaquetopenia e DHL elevado foram significativamente maiores em LLA versus AIJs (88% vs. 57%, p<0,0001; 39% vs. 1%, p<0,0001; 60% vs. 1%, p<0,0001; 77% vs. 1%, p<0,0001; 56% vs. 14%, p<0,0001; respectivamente). Consideravelmente, a análise multivariada mostrou que dor em membros (OR=553; 95% IC=46,48-6580,42; p<0,0001) e plaquetopenia (OR=754,13; 95% IC=64,57-8806,72; p<0,0001) permaneceram como variáveis independentes que diferenciaram pacientes com LLA de pacientes com AIJs. O R2 de Nagelkerke foi de 0,91. A curva de sobrevida de Kaplan-Meier foi similar em pacientes com LLA com e sem dor em membros (p=0,8347). Conclusão: O presente estudo enfatiza a importância de investigar pacientes com LLA que apresentam manifestações musculoesqueléticas, particularmente dor em membros com plaquetopenia

Objective: To assess clinical and laboratorial features which differentiate acute lymphoblastic leukemia (ALL) from systemic onset juvenile idiopathic arthritis (SoJIA) at disease onset. Methods: Fifty seven ALL patients with musculoskeletal involvement, without blasts on peripheral blood and glucocorticoid therapy at onset of disease and 102 SoJIA patients (ILAR criteria) were retrospectively evaluated. The following features were studied: fever, rheumatoid rash, arthritis, limb pain, hepatomegaly, splenomegaly, pericarditis, myocarditis, pleuritis, weight loss, bleeding, anemia, leukopenia, neutropenia, thrombocytopenia, high erythrocyte sedimentation rate and high lactic dehydrogenase (LDH) levels. Results: The median age at disease onset was significantly higher in ALL compared to SoJIA patients (5.8 vs. 3.8years, p=0.0006). The frequencies of limb pain, hepatomegaly, weight loss and hemorrhagic manifestations were significantly higher in ALL versus SoJIA patients (70% vs. 1%, p<0.0001; 54% vs. 32%, p=0.0075; 30% vs. 8%, p=0.0005; 98% vs. 0%, p=0.0053; respectively). Likewise, the frequencies of anemia, leukopenia, neutropenia, thrombocytopenia and high LDH levels were significantly higher in ALL versus SoJIA patients (88% vs. 57%, p<0.0001; 39% vs. 1%, p<0.0001; 60% vs. 1%, p<0.0001; 77% vs. 1%, p<0.0001; 56% vs. 14%, p<0.0001; respectively). Remarkably, multivariate analysis showed that limb pain (OR=553; 95% CI=46.48-6580.42; p<0.0001) and thrombocytopenia (OR=754.13; 95% CI=64.57-8806.72; p<0.0001) remained as independent variables that differentiate ALL from SoJIA patients. The R2 of Nagelkerke was 0.91. The Kaplan-Meier survival curves were similar in ALL patients with and without limb pain (p=0.8347). Conclusion: The present study emphasizes the importance to investigate ALL patients who have musculoskeletal manifestations, particularly limb pain associated with thrombocytopenia