In addition, the ACD gene coding for TPP1, which caps the telomere ends and recruits telomerase [159,160,161,162,163,164,165], was associated with such stem cell diseases as aplastic anemia with bone marrow failure [166] and Hoyeraal–Hreidarsson syndrome [167], and the expression levels of TPP1 were significantly reduced in the lung tissue of patients with chronic obstructive pulmonary disease (COPD) [168]. Here, TPP1 is linked to idiopathic aplastic anemia.