Morphological Spectrum of Paroxysmal Nocturnal Hemoglobinuria (PNH)

Paroxysmal nocturnal hemoglobinuria in a patient post COVID-19 virus infection: A case report with literature review

COVID 19 is a serious infection that originated in Wuhan, China and has resulted in worldwide morbidity and mortality. It continues to be a major health concern in 2022, being associated with multiorgan failure. Although the pathophysiology of the disease and its complications are not well understood, it is believed that a cytokine storm, triggered by complement activation may be responsible for the severity and complications of the disease. As of now, there is no definitive treatment available. Hematological changes associated with COVID-19 include lymphopenia, anemia, thrombocytopenia, disseminated intravascular coagulopathy, and thrombosis. Paroxysmal nocturnal hemoglobinuria (PNH), on the other hand, is an acquired clonal hematopoietic stem cell disorder that occurs due to an acquired PIG-A mutation affecting the hematopoietic stem cells. Interestingly, PNH exhibits some clinical and laboratory manifestations like those seen in COVID-19. In this report, we present a rare case of PNH that developed following a COVID-19 infection.

Secondary myelodysplastic syndrome and leukemia in acquired aplastic anemia and paroxysmal nocturnal hemoglobinuria

Acquired aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH) are pathogenically related nonmalignant bone marrow failure disorders linked to T-cell-mediated autoimmunity; they are associated with an increased risk of secondary myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Approximately 15% to 20% of AA patients and 2% to 6% of PNH patients go on to develop secondary MDS/AML by 10 years of follow-up. Factors determining an individual patient's risk of malignant transformation remain poorly defined. Recent studies identified nearly ubiquitous clonal hematopoiesis (CH) in AA patients. Similarly, CH with additional, non-PIGA, somatic alterations occurs in the majority of patients with PNH. Factors associated with progression to secondary MDS/AML include longer duration of disease, increased telomere attrition, presence of adverse prognostic mutations, and multiple mutations, particularly when occurring early in the disease course and at a high allelic burden. Here, we will review the prevalence and characteristics of somatic alterations in AA and PNH and will explore their prognostic significance and mechanisms of clonal selection. We will then discuss the available data on post-AA and post-PNH progression to secondary MDS/AML and provide practical guidance for approaching patients with PNH and AA who have CH.