CFE in N-BMSCs and those derived from patients with TBD. (A) CFE of freshly isolated cells (from bone fragments from surgical waste or from Jamshidi needles) from normal donors (N, n = 11), TBD patients (n = 9, patients 1 [TERC], 2 [TINF2], 3 [RETL1], 4 [TERC], 5 [TERT], 6 [RETL1], 9 [WRAP53], 10 [no telomere-related mutation found to date], 11 [TINF2]), and from patients with other forms of BMF, SDS (n = 4), and DBA (n = 4) was determined. CFE (to date, the closest approximation of the number of skeletal stem cells within the freshly isolated BM) was reduced in TBD samples compared with normal (*P ≤ .0001), and SDS and DBA samples. A freshly isolated sample from a previous patient with AAA was also normal (see supplemental Figure 1). (B) At P1, BMSCs were assayed for secondary CFE from normal donors, and from all patients with TBD (n = 11), SDS, DBA, and AAA. TBD-BMSCs demonstrated a reduced capacity to form secondary colonies in comparison with the normal, SDS, and DBA BMSCs (*P ≤ .0001). Unlike TBD-BMSCs, BMSCs from AAA patients, who displayed a similar pattern of BMF as TBD patients, showed normal secondary CFE.