OPSI threat in hematological patients

Abstract

Overwhelming post-splenectomy infection (OPSI) is a rare medical emergency, mainly caused by encapsulated bacteria, shortly progressing from a mild flu-like syndrome to a fulminant, potentially fatal, sepsis. The risk of OPSI is higher in children and in patients with underlying benign or malignant hematological disorders. We retrospectively assessed OPSI magnitude in a high risk cohort of 162 adult splenectomized patients with malignant (19%) and non malignant (81%) hematological diseases, over a 25-year period: 59 of them splenectomized after immunization against encapsulated bacteria, and 103, splenectomized in the previous 12-year study, receiving only life-long oral penicillin prophylaxis. The influence of splenectomy on the immune system, as well as the incidence, diagnosis, risk factors, preventive measures and management of OPSI are also outlined. OPSI occurred in 7 patients (4%) with a median age of 37 years at time interval from splenectomy ranging from 10 days to 12 years. All OPSIs occurred in non immunized patients, except one fatal Staphylococcus aureus -mediated OPSI in a patient adequately immunized before splenectomy. Our analysis further provides evidence that OPSI is a lifelong risk and that current immune prophylaxis significantly decreases OPSI development. Improvement in patients' education about long-term risk of OPSI and increased physician awareness to face a potentially lethal medical emergency, according to the current surviving sepsis guidelines, represent mandatory strategies for preventing and managing OPSI appropriately.

Keywords: Overwhelming postsplenectomy infection (OPSI) syndrome; hematological disorders; splenectomy.

Figure 1.

Antimicrobial splenic functions. Compartments of white pulp involved in protective antimicrobial functions: a) periarteriolar lymphoid sheats (PALS) through ① secretion of T-dependent immunoglobulins (Ig) and ② antigen presentation to T-Lymphocyte by marginal zone (MZ) macrophages; b) follicles through ③ MZ macrophage-mediated activation of B lymphocytes and plasmacells and ④ production of antibodies, complement and opsonins; c) marginal zone through ⑤ opsonin-independent phagocytosis mediated by MZ macrophages, ⑥ presentation of particulate antigens by MZ macrophages to CD27+IgM+ B cells, ⑦ rapid release of antibodies by CD27+IgM+ memory B cells, ⑧ opsonin-dependent phagocytosis by MZ macrophages. Red pulp exerts anti-microbial protective functions mainly through ⑨ blood-borne pathogens filtering, culling and pitting of red blood cells (RBC) and ⑩ rapid GM-CSF release via innate response activator (IRA) and antibodies by B cells and plasmacells. Symbols: Ig = ; T-cell receptor/Major hystocompatibility complex binding, ; complement, ;opsonin, ; pathogen-recognition-receptors (PRRs), ; particulate antigen, ; GM-CSF (Granulocyte-macrophage colony-stimulating factor), .

Figure 2.

Howell-Jolly bodies. Howell-Jolly bodies (red arrows) in circulating red blood cells of a patient with OPSI.