• Efficacy of tocilizumab as defined by presence of an equal to or greater than 30% improvement in JIA core set (i.e. ACR JIA30 response) [ Time Frame: At week 12 of treatment versus week 0 (pretreatment) ] [ Designated as safety issue: No ]
  
• Efficacy of tocilizumab as defined by reduction of oral prednisone dose by at least 20%, or to less than 0.5mg/kg/day, whichever is of lesser daily dose, while maintaining an ACR JIA30 response [ Time Frame: At weeks 12 and 16 of treatment versus week 0 (pretreatment) ] [ Designated as safety issue: No ]
  
• To evaluate the safety of tocilizumab administration in this subject [ Time Frame: Ongoing, throughout 24 month study period ] [ Designated as safety issue: Yes ]
  

• To assess normalization of laboratory parameters of active disease, specifically C-reactive protein, hemoglobin, platelets, white blood cell count, ferritin, immunoglobulins. [ Time Frame: At weeks 8, 12, and 16 of treatment, and every 8-12 weeks thereafter ] [ Designated as safety issue: Yes ]
  
• To assess sustained clinical response to tocilizumab, including active joint count, joints with limited range of motion, and absence of fever or rash. [ Time Frame: At weeks 8, 12, 16 of treatment, and every 8 weeks thereafter ] [ Designated as safety issue: No ]
  

Biological: tocilizumab

Initial therapy: Tocilizumab dosed by body weight (8mg/kg based on body weight ≥ 30kg) given by intravenous infusion every two weeks for 12 weeks.

Extension of therapy: Continuation of treatment with tocilizumab at 8mg/kg by body weight given by intravenous infusion every 2 weeks based upon achievement of Primary Objective by week 12, OR continuation of treatment with escalation of tocilizumab dose to 12mg/kg by body weight, given by intravenous infusion every two weeks, for failure to achieve ACR JIA30 at 12 weeks or ACR JIA50 response at any time after week 16.

Systemic onset Juvenile Idiopathic Arthritis (soJIA) is a type of arthritis (inflammation of the joints) that occurs with other symptoms including fever, swollen lymph nodes (glands), rash, and body aches. Because soJIA can be difficult to treat, children with soJIA can have severe problems from long-term use of steroids (prednisone). These problems include low bone density (weak bones), fractures, failure to grow properly, and large weight gain. The arthritis that occurs in soJIA often causes damage to many joints. This can make it hard to move around or do basic tasks like dressing. Also, a life-threatening illness called Macrophage Activation Syndrome (MAS) can occur when starting, stopping, or changing drugs that are used to treat soJIA.

SoJIA can be hard to treat and many children with soJIA do not respond to drugs that work for other kinds of arthritis. Research doctors have studied a chemical signal called IL-6 that the body uses to manage inflammation. This signal has been found to be very high in patients with active soJIA. A drug called tocilizumab (TCZ) has been designed to block IL-6. For about 6 years, TCZ has been tested in Japan for treating soJIA. It is now being tested in studies in the United States. These studies can have very strict rules for enrolling patients. This trial is a single-patient research study for a subject who otherwise does not meet the rules for enrollment in ongoing trials.