Juvenile Idiopathic Arthritis (Juvenile Rheumatoid Arthritis)

Essentials

• Symptom start is usually insidious. The child seldom complains of pain.
• The joints should be systematically examined Articular Status of a Child with Arthritic Symptoms in all children with suspected arthritis.
• Further diagnostic investigations are always performed and long-term decisions on treatment made at a specialized unit.

Definition and epidemiology

• Juvenile idiopathic arthritis (JIA) was formerly referred to as juvenile rheumatoid arthritis (JRA).
• Arthritis lasting for more than six months is considered to be JIA if other causes of arthritis have been ruled out with sufficient certainty.
• The incidence of the disease is 15-19/100 000 and its prevalence about 1/1000.

Signs and symptoms

• Morning stiffness and a limp are the most common initial symptoms.
• The child seldom complains of pain (limping relieves pain at the ankle or knee!).
• Ankle, knee and hip are the most often affected joints, with swelling and/or restricted and painful movement as the usual findings.
• Arthritis affecting the upper limbs often presents itself as a change in the way the child uses his/her hand or the parents notice a swollen finger.
• Prolonged neck pain and torticollis may be an early symptom of JIA affecting the cervical spine.
• Often clinical signs can be elicited only by systematic joint examination Articular Status of a Child with Arthritic Symptoms.
• In systemic JIA (Still's disease), the only symptoms for a long time may be remittent fever and erythematous macular rash on the upper trunk during the episodes of fever Fever in a Child.

Investigations in suspected JIA

• JIA is a diagnosis of exclusion; see article Arthritis in children Arthritis in Children.
• Basic blood count with platelet count, CRP, ESR, streptococcal throat culture and chemical urinalysis are examined in all patients.
• If the symptoms have lasted for more than 2 weeks, examine antinuclear antibodies, streptococcal antibodies (ASO and anti-DNase B), as well as antibodies against Borrelia, Yersinia, Campylobacter and Salmonella (if there is a history of diarrhoea and the child is over 5 years of age).
• Imaging studies (ultrasonography or x-ray) in unclear cases and when the symptom or finding is focal, i.e. limited to one location

Subtypes of JIA

1. Oligoarthritis (1-4 affected joints, about 50% of all patients)
   • Onset usually before school age.
   • The majority of the patients are girls.
   • In most cases the knee or the ankle are initially affected.
   • Antinuclear antibodies (ANAs) are detected in 80% of cases.
   • About one third of the patients have chronic, usually asymptomatic iridocyclitis that may even result in loss of vision if left untreated.
   • The prognosis is good.
   • There are two distinct types:
     • 1a. The disease remains oligoarticular (only 1-4 affected joints)
     • 1b. The disease progresses to affect several joints when at least 6 months have elapsed since the onset (about 20-30% of oligoarthritides)
2. Enthesitis-related arthritis (approximately 10% of all patients)
   • Large joints of the lower limbs, including the sacroiliac joints, are affected.
   • Occurs in children aged 6-15 years.
   • The majority of the patients are boys.
   • HLA-B27 is positive in 75% of cases.
   • Insertitis (enthesitis) is a common clinical feature.
3. Seronegative polyarthritis (about 30% of all patients)
   • Occurs in children aged 1-15 years.
   • In addition to large joints, also small joints, the temporomandibular joints and the cervical spine are often affected.
   • The majority of the patients are girls.
   • ANAs are detected in 25% of cases.
4. Seropositive polyarthritis (< 5% of all patients)
   • Occurs in children aged 8-15 years.
   • The same disease as seropositive rheumatoid arthritis in adults
   • The majority of the patients are girls.
   • The test for rheumatoid factor is positive.
   • Bony erosions develop quicker than in the other disease forms.
5. Systemic JIA (< 5% of all patients)
   • Fever and rash are the initial symptoms. Joint symptoms develop later or, in some cases, not at all.
   • Neutrophilic leucocytosis and increased ESR and CRP are detected.
   • Tests for ANAs and rheumatoid factor are negative.
   • About 50% of the patients develop polyarthritis.
6. Psoriatic arthritis (< 5%) refers to a condition where the child has psoriasis (rare) concomitantly with chronic arthritis. The disease is classified as psoriatic arthritis also if, in addition to arthritis, the patient has at least 2 of the following: dactylitis, typical nail abnormalities or a first degree relative with psoriasis.

Principles of treatment Exercise Therapy in Juvenile Idiopathic Arthritis, Methotrexate for Treating Juvenile Idiopathic Arthritis

• Treatment decisions are made in specialized care where a multidisciplinary team is responsible for the treatment.
• The aim of treatment should be to guarantee normal growth and functional capacity and to prevent malpositions and damage to the joints.
• Non-steroidal anti-inflammatory drugs may be taken as required (naproxen, 10-20 mg/kg/day, diclofenac 1-3 mg/kg/day, ibuprofen 20-40 mg/kg/day). Cold packs relieve pain and swelling. NSAID medication and cold pack therapy can already be started when there is only a suspicion of the disease.
• Local glucocorticoids can be injected in joints with hydrops or moderate or severe symptoms (administered under general anaesthesia in children).
• Weekly methotrexate has become the gold standard of systemic treatment. Alternative treatments are used if methotrexate is ineffective or it has excessive adverse effects.
• Alternatives to methotrexate include sulphasalazine (leflunomide and azathioprine).
• If adequate treatment response is not achieved with the aforementioned monotherapies, a combination of several antirheumatic drugs or biologic-response modifiers (biologics) may be tried. The latter group includes tumour necrosis factor (TNF) inhibitors, interleukin-1 and interleukin-6 inhibitors, as well as drugs directed at T and B lymphocytes.
• Laboratory tests for monitoring drug safety may be carried out in primary care; see table in article Rheumatoid arthritis Rheumatoid Arthritis.
• Physiotherapy should be provided as required.
• Vaccinations should preferably be given during remission.
• As a rule, infections in a child with juvenile idiopathic arthritis are treated according to general principles. If there is a suspicion of tuberculosis contact in a patient on antirheumatic medication or a suspicion of varicella contact in a patient not vaccinated against varicella, the specialist responsible for the child's treatment should be contacted without delay.
• Coping with the disease at school requires cooperation between the teachers and parents. Career choice counselling is important in adolescence if the child continues to have symptoms.

Referral criteria and follow-up

• If there is a suspicion of juvenile idiopathic arthritis (always when a limitation in the range of joint motion is detected or when the symptoms have lasted for several weeks and the joint swelling persists despite NSAID medication), the patient is referred to a specialist unit. The treatment in the acute phase of the disease is the responsibility of a specialist experienced in JIA.