We recently discovered that patients with a germline or somatic CHIP (clonal haematopoiesis of indeterminate potential) mutation in Tet methylcytosine dioxygenase 2 (TET2), a gene which encodes TET2, and a major enzyme mediating DNA demethylation, exhibit greater inflammation compared with those with PAH without such a mutation [5,84]. This evidence concerns the gene TET2 and pulmonary arterial hypertension.