A link between inherited and somatic mutations in the pathogenesis of sideroblastic anemia. Schematic representation of the process that may lead to the phenotypic expression of XLSA in a woman who is heterozygous for an ALAS2 mutation. ALAS2^WT indicates wild-type allele; ALAS2^Mut, mutant allele. The development of age-associated clonal hematopoiesis—in this example caused by the occurrence of a somatic mutation of DNMT3A—may lead to the selective expansion of a hematopoietic stem cell that expresses the X chromosome carrying the mutant ALAS2 allele. This would in turn lead to the phenotypic expression of XLSA, as happens in hemizygous males. The interaction between XLSA and clonal hematopoiesis may alter some features of XLSA, such as the MCV, which can be borderline (∼80 fL) in patients with clonal hematopoiesis rather than markedly decreased (60-70 fL) as it is in typical hemizygous males.