Arthritis Foundation;Juvenile arthritis information.Twenty-year-old Kelly Slauson doesn’t know life without rheumatoid arthritis.Diagnosed when she was just 18 months old, Slauson’s life as she knows it has always included medications, doctor’s appointments and joint stiffness.“I thought every kid had to get shots on Friday nights and go to the doctor all the time,” said Slauson, who lives in Camas.When Slauson was only about 7 or 8 months old, she started walking. But her parents later realized something wasn’t right.Slauson would walk, but then, after napping, would wake up and revert to crawling. Or, if she did walk, it would be with a limp. Her pediatrician referred her to a rheumatologist at Seattle Children’s Hospital, where she was diagnosed with rheumatoid arthritis, an autoimmune disorder in which the immune system mistakenly attacks the body’s own tissue. Rheumatoid arthritis is a chronic inflammatory disorder that affects the lining of the joints, causing a painful swelling that can eventually result in bone erosion and joint deformity, according to the Mayo Clinic.Rheumatoid arthritis typically begins between the ages of 40 and 60. Among children younger than 16, juvenile rheumatoid arthritis is the most common type of arthritis. Symptoms of juvenile rheumatoid arthritis typically begin before age 16 and can appear in children as young as 6 months, according to the National Institutes of Health.