Previous research has shown that in phaeochromocytomas, chromaffin cells (a type of endocrine cell located in the adrenal medulla in charge of producing and secreting catecholamines) preserve ETC complex I (CI) function despite the loss of SDH-b, unlike other cell types (Kluckova and Tennant 2018; Kl’učková et al. Here, SDHB is linked to pheochromocytoma.