Extrahematopoietic Manifestations of Telomere Syndromes

Abnormally short telomeres give rise to a group of premature aging, cancer-prone disorders known as the telomere syndromes. They are caused by germline mutations in telomerase and telomere genes. Although bone marrow failure was one of the first complications to be described in dyskeratosis congenita, there is increasing appreciation that this classic presentation is rare. Extra-hematopoietic telomere-mediated disease is frequently the first and predominant presentation in adults and leads to significant morbidity and mortality in patients with bone marrow failure (BMF), especially after bone marrow transplantation. It shows stereotypic manifestations that are age-dependent. Enterocolitis can precede the onset of BMF in infants with Hoyeraal-Hreidarsson syndrome, and it represents an intestinal epithelial defect that progresses in the setting of immunodeficiency. In adults with familial lung disease, idiopathic pulmonary fibrosis and emphysema are the predominant manifestations. These patients show variable degrees of BMF and are at risk for clonal abnormalities. In the lung transplant setting, adult telomere syndrome patients have an increased risk of complications due to immunosuppressive medications which challenge their reserves in the bone marrow, intestinal tract and elsewhere. Liver disease, often manifesting as hepatopulmonary syndrome, causes organ failure in approximately 10% of cases. The molecular mechanisms underlying telomere-mediated disease outside the bone marrow likely involve stem cell failure. For example, in the lung, alveolar stem cell senescence is sufficient to drive remodeling, inflammation, and susceptibility to injury, which are hallmark features of pulmonary fibrosis and emphysema. The stem cell failure mechanism has implications for approaching treatment in these lung disorders which have heretofore been considered mediated by inflammation. This session will present evolving scientific evidence that sheds light on the mechanisms and natural history of telomere syndromes. Considerations in the diagnostic work-up of suspected cases and the implications for patient care will be reviewed.