BACKGROUND With an incidence of 4%, acute pancreatitis is a common complication of bone marrow or peripheral haematopoietic stem cell transplantation, which contributes significantly to morbidity and mortality in these patients. In most cases, the pathogenesis of acute pancreatitis cannot be attributed to a single pathogenetic factor, as treatment toxicity, acute graft versus host disease, infection, and cholestasis may all contribute. Acute pancreatitis is characterised by inflammation and activation of digestive proenzymes leading to autodigestive destruction of the pancreas and systemic activation of protease cascades including the complement system.

AIM To describe the effects of human C1 esterase inhibitor in two children, who developed severe acute pancreatitis with considerable complement activation after allogeneic haematopoietic stem cell transplantation.

CONCLUSIONS These observations strongly support the proposed pathophysiological concept that early treatment with C1 esterase inhibitor interferes with the activation of the complement system in acute pancreatitis. Inhibition of complement activation prevents its adverse effects on vascular function and permeability, and thus stabilises intravascular fluid status and prevents multiorgan failure in acute pancreatitis.