Where the TRM risk is small and the severity/prognosis of the underlying disease is well-understood and predictable the “pre-emptive” use of HSCT is justifiable, examples of specific PID in this category include chronic granulomatous disease (CGD), Wiskott-Aldrich Syndrome (WAS), primary HLH and GATA2 Deficiency. Here, GATA2 is linked to Wiskott-Aldrich syndrome.