Extension Study (Extended Access) of Syk-inhibition Using Fostamatinib to Treat Posttransplant Immune-mediated Cytopenias

Subjects will receive fostamatinib at the same dose as the dose they receive at the time of rollover. The dose could be reduced to 100mg daily, 150 mg daily, 100 mg twice a day if a dose-limiting adverse event occurred. After the initial 12 weeks on the extended access (total of 24 weeks of treatment), subjects will have the option to start tapering fostamatinib if they are maintaining hematologic recovery. Subjects with persistent (=2 readings, 2 weeks apart) loss of hematologic response, defined as Hb\<9g/dL and/or PLT\< 30 X 10\^9/L can increase their dose to next higher dose. Once count stabilization again occurs, a slow dose reduction to next lowest dose (100mg or 150mg) can be performed to identify the lowest dose necessary to keep counts over these thresholds.