Sequelae include morning stiffness with warmth, painful motion or resisting the full range of motion. Muscle atrophy of affected extremities combined with accelerated growth may occur. A child with unilateral gonarthritis typically presents with a discrepancy in leg length resulting in a flexion and outward rotation of the affected knee. Acute phase reactants are normal or moderately increased, but a high Erythrocyte Sedimentation Rate (ESR) can also occur. Antinuclear antibodies (ANAs) are detected in about 60% of patients. Oligoarthritis predominately affects females; they are at high risk for developing uveitis. The presence of ANAs conveys a risk of iridocyclitis, an inflammation of the iris and ciliary body of the eye.23 Iridocyclitis affects approximately 30% of patients with oligoarthritis. Although iridocyclitis can precede arthritis, it usually manifests itself within the first few years after the onset of arthritis. Due to its insidious and often asymptomatic onset, children with JIA should be screened at regular intervals by slit-lamp examination. Rheumatoid Factor-Negative (RF-) Polyarthritis – This pathology is defined as an arthritis that affects five or more joints during the first six months of the disease.21 Patients often develop polyarthritis in early childhood. This subtype affects girls more frequently than boys and it has a variable prognosis. By definition, immunoglobulin-M rheumatoid factor (IgM-RF) is negative, and this subtype involves multiple large and small joints, very often in a symmetric fashion. The onset can be acute or insidious. Pain, confined movements and morning stiffness are the most prominent symptoms. Some patients with polyarthritis especially those who are ANA positive, could be classified as having oligoarthritis, except that more joints are involved. Other patients present with only slight small joint swelling, but have pronounced stiffness and flexion contractions and a normal ESR. These patients are especially hard to diagnose. Rheumatoid Factor-Positive (RF+) Polyarthritis – This subtype is probably identical to the rheumatoid arthritis seen in adults. RF+ polyarthritis occurs primarily in late childhood and adolescent girls as a symmetric small joint involvement and severe erosive disease. It affects the small joints of the hands and feet including the metacarpophalangeal, proximal interphalangeal and metatarsophalangeal joints. Rheumatoid nodules sometimes appear on the extensor surfaces of the elbows. By definition, the presence of IgM-RF is mandatory and probably represents the early expression of adult rheumatoid arthritis; however, anticyclic citrullinated peptide antibodies may also be of interest since they have been observed in adult patients with rheumatoid arthritis. Enthesitis-Related Arthritis (ERA) – Patients with juvenile ankylosing spondylitis and arthritis associated with inflammatory bowel disease are included in the ERA subtype. This is the only subtype of JIA that affects more males than females, older than 8 years of age, and it comprises approximately 10 to 15% of all patients with JIA. It is characterized by a combination of chronic arthritis of the axial and periphereal skeleton, enthesitis (tenderness at the insertion of a tendon, ligament, joint capsule or fascia to the bone), RF and ANA seronegatively. It has a strong genetic predisposition and most patients express HLA-B27, long known to be associated with arthritis; however, the etiology of enthesitis related arthritis is still unknown.24 32 Vol. 63, No. 3 2012 Northeast Florida Medicine
The hallmarks of the disease are pain, stiffness, and loss of mobility of the back. Involvement of the hip joint, an effect sometimes seen in this subgroup, can progress to include the sacroiliac joints and other joints of the axial skeleton, finally resulting in (juvenile) ankylosing spondylitis.25 Arthritis frequently affects the joints of the lower extremities, and the typical localization of the enthesitis is the calcaneal insertion of the Achilles tendon. Four or fewer joints are usually affected, but the disease can also take a polyarticular course. Extra-articular manifestations include anterior acute uveitis, aortic insufficiency, aortitis, muscle weakness, and low-grade fever. Laboratory data may show mild anemia, a normal to moderately elevated white blood cell count, thrombocytosis and elevated sedimentation rate.26, 27 Psoriatic Arthritis – Psoriatic arthritis is defined as a chronic inflammatory arthritis with psoriasis, with a peak age of onset in mid-childhood. In children, arthritis can precede psoriasis for many years. That is why this subtype is a difficult diagnosis. Often larger joints are affected in an asymmetric fashion, but small joints can have this arthritis, namely the knees and ankles and the small joints of the hands and feet. Proximal interphalangeal joints, distal interphalangeal joints, and the tendon sheath are often inflamed, resulting in the diffuse swelling of the digit known as the “sausage digit”.28 By definition, the presence of dactylitis, nail pitting, onycholysis or a positive family history supports the diagnosis; however, many children classified as having psoriatic arthritis according to the ILAR criteria might be better classified as having oligoarticular disease. Therefore, the definition of juvenile psoriatic arthritis is under scrutiny.25 Laboratory data show elevated acute-phase reactants, anemia of chronic disease, and thrombocytosis, ANA may be positive. Undifferentiated Arthritis – This subgroup includes patients who do not fulfill the criteria of any of the other categories or who would fit into two or more subgroups. This category, therefore, does not represent a separate clinical subgroup.
Conclusion Juvenile idiopathic arthritis is one of the most common rheumatic diseases of childhood and is a significant cause of short and long term disability. The classification of JIA has been modifies over the recent decades. Three primarily classification have been adopted in recent past; first by the American College of Rheumatology (ACR), second by the European League Against Rheumatism (EULAR) conference and third by the International League of Associations for Rheumatology (ILAR). These classification schemes were developed to facilitate communication regarding epidemiology, therapeutics, and outcomes among physicians globally. They are recognized based on the clinical features during the first 6 months of disease. The current JIA classification still has shortcomings and will remain imperfect until enough is known about pathophysiology and genetics of disease.
References
1.
Fink CW. Proposal for the development of classification criteria for idiopathic arthritides of childhood. J Rheumatol 1995; 22:1566.
2.
Petty RE, Southwood TR, Baum J, et al. Revision of the
www . DCMS online . org