RTEL1 and Tangier disease: Depletion of some iron-containing proteins such as DNA polymerases Polα, δ, and ε, Regulator of telomere length 1 (RTEL1), and the small subunit of Ribonucleotide reductase (RNR) results in abnormal TL.35–37 Moreover, patients with diseases caused by iron deficiency or iron overload also have short TL.38,39