*1.7. Undi*ff*erentiated Arthritis*

Undifferentiated JIA is a subtype of juvenile arthritis that does not exactly meet the criteria for the categories mentioned above, or it simultaneously meets several criteria for different subtypes of the disease [2].

The Paediatric Rheumatology INternational Trials Organisation (PRINTO) has a current project with the proposal to revise current JIA classification criteria after ILAR, using clinical evidence and common laboratory data available worldwide to classify those forms of chronic arthritis that are commonly encountered in children and that are the counterpart of childhood diseases observed in adults [19].
