This interesting article attempts to elucidate the mechanism leading to microcytosis and anemia in patients treated with sirolimus (SRL), an mTOR inhibitor, following allogeneic kidney or kidney-pancreas transplantation, a development that could raise the suspicion of blood loss and could lead to invasive diagnostic procedures. The authors were able to show that microcytosis is reversed by discontinuation of SRL or by intravenous but not oral iron administration, thus hypothesizing the existence of a state of functional iron deficiency induced via an effect of SRL on hepcidin.

– Alice Maniatis