AMD 3100 for Treatment of Myelokathexis

This is an open label, single Center, phase I study to examine the hematological effects, pharmacokinetics and safety of plerixafor in patients with myelokathexis attributable to mutations of CXCR4, utilizing serial, escalating doses of plerixafor administered on days 1, 3, 5, 8, and 10. Five intrapatient escalating dose levels, 20 micrograms per kilogram (mcg/kg), 40 micrograms/kilogram(mcg/kg), 80 micrograms/kilogram(mcg/kg), and 240 micrograms/kilogram (mcg/kg)will be examined. The subjects will be patients at the University of Washington General Clinical Research Center for up to 10 days; the study requires subject be available for up to 14 days. Patients will be monitored for hematological effects of plerixafor and observed for adverse effects. If a normal blood neutrophil count is achieved and maintained for at least 24 hours prior to the highest dose, we will stop at that level.