Introduction

Since the seminal description of its symptoms by Paul Strübing in 1882 (Strübing, 1882), paroxysmal nocturnal hemoglobinuria (PNH) has captured the attention of physicians and researchers. PNH is an acquired chronic hemolytic anemia, that is classically more frequent at night, and is often associated with neutropenia and/or thrombocytopenia, and episodes of venous thrombosis (Rosse, 1995). From the clinical point of view, the interrelationship between aplastic anemia (AA) and PNH has long been recognized. More than 50 years ago, Dacie and Gilpin (1944) were the first to describe a patient with AA–PNH syndrome and in 1967 Dr Dameshek stated in an editorial that, ‘Aplastic anemia, and PNH might have a common denominator in the form of an insult to the marrow’ (Dameshek, 1967). Marrow function is frequently found to be impaired in those with PNH, as shown by pancytopenia and a relatively low reticulocyte count in light of the degree of anemia (reviewed by Rosse, 1995). In a number of patients [8-year cumulative incidence rate of 15% (Socié et al., 1996)], moderate to severe marrow failure may occur during the course of the disease. Another group of patients has long been recognized: their first diagnosis is AA, but they go on to develop PNH. Thus, clinically PNH may be considered as a disease that presents in two forms: de novo PNH and the AA–PNH syndrome.