This is an open-label single-arm uncontrolled trial with biologic endpoint. This study will use tocilizumab in subjects with HLH and high cytokine levels in an attempt to decrease the damage caused by these proteins. All subjects will receive standard therapy, in addition to tocilizumab. We hypothesize the tocilizumab will decrease levels of certain important cytokines. This may make it easier to treat subjects with HLH overall.