STAT1 and progressive multifocal leukoencephalopathy: To date, mutations in 11 IUIS genes (BTK, CD40LG, DOCK8, MAGT1, NFKB1, PRKDC, RAG1, RMRP, STAT1, STK4, and WAS) have been reported in PML patients, most frequently for DOCK8 (3 cases) (28, 31) and STAT1 (4 cases) (26, 32).