CD34 and hereditary hemorrhagic telangiectasia: Moreover, Zucco et al. (2014) reported that the percentage of CD34+ cells in peripheral blood mononuclear cells from HHT patients was significantly higher than in controls. Interestingly, the CD34+ cell subset has been involved in the repair of damaged vessels (Yoder, 2012) and its increased numbers could give some hints regarding the severity of the vascular lesions in HHT.