The diagnosis of<unk>  can be difficult, in part because joint pain in children is so common and may be from many causes other than<unk> . The characteristic feature of arthritis is joint swelling which is sometimes – but not always – associated with pain. The presence of joint stiffness is another typical feature, particularly when present in the morning and improving with activity. No single test can confirm a diagnosis of<unk> : a combination of presenting signs and symptoms, blood tests, and if necessary medical imaging, is used to make the diagnosis. The blood tests may measure levels of inflammatory markers, as well as the presence of specific immune markers which may include anti-nuclear antibody, HLA-B27, rheumatoid factor and anti–citrullinated protein antibody. These serological markers may be negative in children with<unk> , and are often present in healthy children; as such they should not be interpreted in isolation but in the context of the clinical presentation. Many children with<unk>  have normal blood work. X-rays may be required to ensure that the joint pain and swelling is not from a fracture, cancer, infection, or congenital abnormality. In some cases, fluid from the joint can be aspirated and analysed to assist in making a diagnosis. This test can assist by ruling out other causes of arthritis such as infection. Classification The current classification system by the International League of Associations for Rheumatology (ILAR) recognizes seven distinct subtypes of<unk> , based on their presentation within the first six months: Each subtype has a specific pattern of features as outlined in the table and descriptions below. (The seventh category, not included in the table, is 'Undifferentiated' and includes any patient with<unk>  who does not meet criteria for other subtypes, or who meets criteria for two or more subtypes). Oligoarticular Polyarticular (RF negative) Polyarticular (RF positive) Systemic Onset Psoriatic Enthesitis Related Arthritis % of<unk>  50-60 20-30 5-10 10-20 5-15 15 Gender (F:M) 4:1 4:1 9:1 1:1 3:2 1:9 Typical age of onset (years) 2-12 (peak 2-3) 2-12 (peak 2-3) Adolescence Any Mid childhood Adolescence Joint Pattern Asymmetric; often large joints (knee, ankle, wrist, elbow) Often asymmetric; multiple small and large joints Symmetric; multiple small and large joints Symmetric; multiple small and large joints Asymmetric; small and large joints including hips and especially DIPs Asymmetric; large joints; axial skeleton Extra-articular Involvement Uveitis in 20% Painless uveitis (especially if ANA positive) Rheumatoid Nodules Fever, rash, lymphadenopathy, enlarged liver and spleen, Serositis Psoriasis, nail pitting, dactylitis, uveitis in 10%, enthesitis Symptomatic uveitis in 20%, enthesitis, IBD, aortitis Oligoarticular arthritis Oligoarticular (or pauciarticular)<unk>  is the most common<unk>  subtype, and occurs when there are up to four joints involved during the first six months of disease. Two subtypes of oligoarticular arthritis exist: persistent oligoarthritis, where no more than four joints are affected throughout the whole disease course; and extended oligoarthritis, where more than four joints are affected after the first six months of disease. Patients in this subtype are often young, typically aged two to three years and with a female preponderance. The most commonly involved joint is the knee, but other affected joints may include the ankles, wrists, elbows and others. The anti-nuclear antigen (ANA) is positive in up to 80% of patients with oligoarthritis and is associated with a higher risk of associated eye disease (uveitis), particularly in younger patients. The prefixes and mean 'few'. Differential diagnosis There are several other disorders and diseases that present with symptoms like<unk> . These causes include, but are not limited to, infectious (for example septic arthritis or osteomyelitis) and post-infectious conditions (reactive arthritis, acute rheumatic fever, and in some geographic areas Lyme disease); hematologic and neoplastic diseases such as leukemia or bony tumors; and other connective tissue diseases (such as systemic lupus erythematosus). For the systemic-onset form of<unk> , the differential diagnosis also includes Kawasaki disease and periodic fever syndromes. Some genetic skeletal dysplasias as forms of mucopolysaccharidosis especially type1 Scheie syndrome, progressive pseudorheumatoid dysplasia and multicentric osteolysis, nodulosis, and arthropathy syndrome may also mimic<unk> , as they may present with joint swelling, joint restriction, stiffness, and pain. The clinical and radiologic overlap between genetic skeletal dysplasias and<unk>  can be great that molecular analysis may be need to confirm the diagnosis. Rarely, metabolic diseases, such as Farber disease may also mimic<unk> . Patients with Farber disease typically have subcutaneous nodules and a hoarse or weak voice due to growth of nodules on the larynx.
Juvenile idiopathic arthritis
Kawasaki disease
Systemic-onset juvenile idiopathic arthritis
Reactive arthritis
Psoriatic arthritis
Rheumatoid arthritis
Relapsing polychondritis
Inflammatory arthritis