XRCC5 and Miyoshi myopathy: There have been a number of reports that indicate Ku86 exists in two forms, an 86 kDa full-length form and a C-terminal truncated variant form of approximately 69-kDa, in B cells from the peripheral blood (PB) [16], the acute promyelocytic leukemia (APL) cell line HL-60 [17], MM cells [5], as well as senescent fibroblasts [18].