Diagnostic algorithm for germline telomere diseases. Mean telomere content should be done in all patients with suspected bone marrow failure from peripheral blood after Fanconi anemia was ruled out in patients under the age of 40 years. Mean telomere content normalized to age-matched controls can be suggestive of telomere disease if below the first percentile or if associated with a strong family history, warranting genetic testing for inherited mutations in telomere maintenance genes. Leukocytes’ telomere content should be interpreted with caution in patients with leukemia (blasts have short telomeres), MDS, and in individuals who have received chemotherapy. If flow-FISH testing is used, the lymphocyte subsets are more accurate than granulocytes. BMF, bone marrow failure; BMT, bone marrow transplant; DEB, deopxybutane; MMC, mitomycin C; PB, peripheral blood.