RTEL1 mutations identified in 4 novel patients. (A) Pedigrees of the patients’ families. (B) Direct Sanger sequencing of the RTEL1 gene in the patients, the healthy siblings, and their parents. Sequencing was performed on DNA extracted from blood samples. Arrows indicate the position of the mutations. (C) Mean telomere lengths of whole blood cells from patients, their parents, and healthy siblings were estimated by the TRF method. The estimated telomere lengths are indicated.