[A reference guide for paroxysmal nocturnal hemoglobinuria: recent updates and points of medical treatment]

Paroxysmal nocturnal hemoglobinuria (PNH) causes clonal expansion of hematopoietic stem cells with abnormal GPI-anchor biosynthesis. The major pathological condition of PNH is that the erythrocytes lacking the complement regulatory factors CD55 and CD59, which are GPI-anchored proteins, lead to intravascular hemolysis through complement activation. Clonal expansion has been assumed to be involved in an immunological attack on hematopoietic stem cells, and the bone marrow failure associated therewith modifies the pathology to varying degrees. The introduction of eculizumab made complement control possible; however, the problems associated with it became apparent as the treatment progressed. Additionally, the PNH Reference Guide was significantly revised in 2016, partly because PNH was designated as a Japanese medical subsidy. With the revised edition of 2020, minor revisions have been added to reflect further advances in treatment and understanding of the disease, while mainly dealing with the clinical introduction of eculizumab derivative, ravulizumab, which uses recycling antibody technology. This review outlines the points of the 2020 revision, including the important points of the previous revision.

[Reference guide for adult chronic neutropenia]

Chronic neutropenia is a rare hematological entity characterized by isolated neutropenia without anemia or thrombocytopenia. The diagnostic criteria and classification of chronic neutropenia have been more elusive in adult cases than pediatric cases. We herein propose the Reference Guide for Adult Chronic Neutropenia. In this guide, diagnosis of chronic neutropenia is based on recurrent or continuous neutropenia defined by absolute neutrophil count (ANC) less than 1,500/µl for over three or more months. Severity of chronic neutropenia is defined as follows: severe, ANC <500/µl; moderate, ANC between 500 and 1,000/µl; mild, ANC between 1,000 and 1,500/µl. In this guide, adult chronic neutropenia is classified into several types including autoimmune neutropenia, cyclic neutropenia, chronic neutropenia with T cell clone, and chronic idiopathic neutropenia with or without family history, and their clinical characteristics are described. Together with antibiotics, granulocyte colony-stimulating factors (G-CSFs) constitute the first-line treatment for adult chronic neutropenia patients at time of bacterial infections. Prophylactic use of G-CSFs or antibiotics is recommended only in selected clinical settings in severe cases.