*1.2. RF-Negative Polyarthritis*

Rheumatoid factor negative polyarticular juvenile idiopathic arthritis is defined by inflammatory damage of 5 or more joints, in the first 6 months after onset, in the absence of RF [14].

According to some authors, this type of juvenile arthritis accounts for up to 30% of polyarticular forms of childhood, and in some cases, it has a rapidly disabling progression [15,16].

This category of polyarthritis is much more severe than oligoarthritis and is often associated with extra-articular manifestations that include salivary gland disease (Sjögren's Syndrome), lymphadenopathy within Felty's Syndrome, or juvenile vasculitis.

About 20% of this category of arthritis starts early, affects the female gender, to whom can be detected positive antinuclear antibodies (ANA), and in these cases, there is a high risk for iridocyclitis. The long-term functional prognosis of the disease is more severe than in the oligoarthritis subtypes, but it is better than in the RF-positive polyarticular JIA [2].
