Introduction
Acquired thrombotic thrombocytopenic purpura (TTP) in children is a rare but severe disease, which can lead to devastating critical organ damage or even death.1 It is caused by Immunoglobulin G (IgG) antibodies, which inactivate a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), which cleaves the ultralarge von Willebrand factor (ULVWF).2 In the absence of active ADAMTS13, ULVWF interacts with platelets, inducing the disseminated formation of platelet-rich thrombi both in circulation and in microvessels, which can result in severe ischaemic tissue damage.3
Daily high-volume plasma exchange (PEX) and immunosuppression with glucocorticoids and rituximab is the current standard of treatment for TTP, which has decreased mortality rates to less than 10%.4-7 Recently, caplacizumab, a nanobody which blocks the A1 domain on ULVWF and prevents its interaction with platelets, has been shown to shorten the interval to remission and also to reduce the likelihood of early death.8 However, a significant proportion of patients have TTP refractory to PEX and immunosuppression, or relapse after achieving remission. We describe the cases of two children with immune-mediated TTP, who relapsed shortly after treatment with PEX, glucocorticoids, and rituximab, and subsequently went into continuous complete remission after one course of bortezomib.