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.