The evolving landscape of hereditary stomatocytosis

Hereditary stomatocytosis represents a heterogeneous group of inherited erythrocyte membrane defects characterized by hemolytic anemia of variable degree, with alterations in cellular salt and water, ranging from dehydration to overhydration, and the presence of stomatocytes on peripheral blood smear. This condition encompasses various subtypes, each with distinct clinical and genetic features. The pathophysiology underlying these conditions involves altered red blood cell membrane properties, leading to impaired deformability and alterations in cation permeability and volume, causing increased susceptibility to hemolysis. Advancements in genetic testing have enabled the identification of some causative genes in the last years, such as PIEZO1, KCNN4, and ABCB6. These genetic discoveries have facilitated a deeper understanding of the molecular mechanisms underlying the pathogenesis and have paved the way for improved diagnostic accuracy and genetic counseling. This review provides an overview of the clinical presentation, pathophysiology, molecular genetics, diagnosis, and management strategies of hereditary stomatocytosis, highlighting recent advancements in the field of dehydrated hereditary stomatocytosis (DHS), or hereditary xerocytosis, and hepatic iron overload. This latter is directly associated with the physiological role of PIEZO1, the causative gene of DHS, at hepatic and macrophagic levels. Particularly, gain-of-function mutations in PIEZO1 account for a pleiotropic syndrome characterized by different phenotypes depending on the expression of PIEZO1 in multiple cells and tissues.