Mutations in the RNA Component of Telomerase, TERC, in Children with Aplastic Anemia and Myelodysplastic Syndrome: An NMDP Study.

Mutations in TERC, the RNA component of telomerase, result in autosomal dominant dyskeratosis congenita (DC), a rare bone marrow failure syndrome. DC is clinically heterogeneous and TERC mutations have been detected in a subset of patients previously diagnosed with idiopathic aplastic anemia (AA) and myelodysplastic syndrome (MDS). Unrecognized TERC mutations are clinically relevant as patients with DC respond poorly to immunotherapy and have an increased risk of complications following conventional conditioning for stem cell transplant (SCT). We aimed to determine the frequency of TERC mutations in pediatric patients with AA and MDS who require a SCT. We obtained 315 blood or bone marrow samples from the National Donor Marrow Program Registry from children under age 18 with bone marrow failure who underwent an unrelated stem cell transplant. We screened these samples for mutations in the TERC gene using direct DNA sequencing. To exclude polymorphisms, we also screened 537 racially diverse healthy controls. The study group was composed of patients with MDS (n=151), AA (n=123), and juvenile myelomonocytic leukemia (JMML) (n=41), which may be difficult to distinguish from MDS. The mean age at the time of transplant was 9 years. We found sequence alterations in the promoter region of TERC in 2 patients. A 2 base pair deletion (-240delCT) was identified in a 4 year-old child with MDS and a 1 year-old child with JMML was found to have a point mutation (-99C→G), which was identified previously in an 18 year-old patient with paroxysmal nocturnal hemoglobinuria and is known to affect the Sp1 binding site. The pathogenicity of this mutation is unclear. In summary, our findings suggest that screening for TERC gene mutations is unlikely to diagnose occult DC in children with severe bone marrow failure who require a stem cell transplant but have no clinical features or history to suggest a familial bone marrow failure syndrome.