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Close relationship between systemic lupus erythematosus and thrombotic thrombocytopenic purpura in childhood.

OBJECTIVE
To determine the association between childhood-onset thrombotic thrombocytopenic purpura (TTP) and systemic lupus erythematosus (SLE).


METHODS
The charts of all 5 patients diagnosed with idiopathic TTP at the Hospital for Sick Children (HSC) in Toronto from 1975 to 1998, and all cases of childhood-onset TTP (ages 6-20 years) reported in the literature over the same period were reviewed. Fourteen of the 44 patients identified in the literature were excluded from the analysis for lack of clinical and laboratory information. The remaining 35 patients were grouped into either an SLE/TTP group or a TTP only group, according to the presence or absence of the American College of Rheumatology (ACR) classification criteria for SLE. The groups were compared for differences in clinical or laboratory features.


RESULTS
The clinical presentation and initial disease course of pediatric patients with TTP were similar to those observed in adults. Of the 35 patients with childhood-onset TTP included in this review, 9 (26%) fulfilled > or = 4 ACR criteria for SLE and 8 (23%) were found to have incipient SLE. Of the 5 patients initially diagnosed with idiopathic TTP at the HSC, 3 were diagnosed with SLE within 3 years, and the other 2 patients fulfilled 3 ACR classification criteria for SLE within 4 years of disease onset. The clinical syndrome of pediatric TTP presenting with proteinuria, especially with high-grade proteinuria, was significantly associated with the development or coexistence of childhood-onset SLE.


CONCLUSION
TTP in childhood is a rare, but life-threatening, disease. Unlike in adults, TTP in childhood is commonly associated with SLE. High-grade proteinuria at diagnosis of TTP is the best predictor for the presence or subsequent development of SLE.