TBI Dose De-escalation for Fanconi Anemia

Day -5 through Day -2, subjects will receive chemotherapy of Cyclophosphamide via central line (i.e. Hickman or Broviac),10 mg/kg intravenously (IV)

Day -5 through Day -2 prior to transplant; subjects will receive chemotherapy of Fludarabine via central line (i.e. Hickman or Broviac),35 mg/m\^2 intravenous (IV)

total body irradiation (300 cGy) with thymic shielding will be given six days before the stem cells are given (day -6). Thymic shielding is done by placing a piece of lead on the chest during the irradiation treatment so that the irradiation beams do not go to the thymus.

A target of 5 \* 10\^6/kg and a minimum of 4 \* 10\^6 CD34+ cell/kg recipient weight will be collected by apheresis and used for transplant. In most cases this dose will be recovered in a single apheresis; however, a second or rarely third apheresis performed on the following days may be required to achieve the minimum dose.

Patients will receive MMF therapy beginning on day -3 through day +30 or for 7 days after engraftment, whichever day is later, if no acute graft-versus-host disease (GVHD). Engraftment is defined as 1st day of 3 consecutive days of absolute neutrophil count \[ANC\] \> 0.5 \* 10\^9/L. MMF will be given at a dose of 15 mg/kg/dose every 8 hours by mouth(to a maximum dose of 1 gram).

Sirolimus will be administered starting at day -3 with 8mg-12mg mg oral loading dose followed by single dose 4 mg/day with a target serum concentration of 3 to 12 mg/mL by high-performance liquid chromatography (HPLC). Levels are to be monitored 3 times/week in the first 2 weeks, weekly until day +60, and as clinically indicated until day +100 post-transplantation. In the absence of acute GVHD sirolimus may be tapered starting at day +100 and eliminated by day +180 post-transplantation.