Juvenile Idiopathic Arthritis

Original Editors - Emily Betz from Bellarmine University's Pathophysiology of Complex Patient Problems project.

Top Contributors - Emily Betz, Lucinda hampton, Jess Bell, Ines Musabyemariya, Admin, Naomi O'Reilly, Khloud Shreif, Kim Jackson, Elaine Lonnemann, Meaghan Rieke, Mande Jooste, Wendy Walker, George Prudden and WikiSysop

This article is currently under review and may not be up to date. Please come back soon to see the finished work! (05/09/2023)

Introduction

Figure.1 Swollen joints in Patient with JIA

Juvenile idiopathic arthritis (JIA) is a term used to describe types of arthritis of unknown cause, where symptoms last for more than 6 weeks, in individuals aged under 16 years at the time of onset.

JIA ranges in severity. It affects the joints, as well as other structures such as the eyes, skin, and organs, and it can be divided into the following subtypes:

• Oligoarticular
• Polyarticular
• Systemic
• Psoriatic
• Enthesitis-related
• Undifferentiated

Aetiology

The aetiology of JIA is unclear. A range of factors have been proposed, including:

• Genetic associations, genetic factors classified into: HLA genes and non-HLA-related genes.
  • HLA class II molecules (A2, DRB1, DPB1) are associated with certain non-systemic JIA types, while systemic JIA is not linked to HLA genes.
• Autoimmune factors
• Environmental factors (e.g. infectious agents, antibiotics, stress etc.) may be risk factors
  • maternal factors (e.g. smoking) may be involved, but breastfeeding / having household siblings may reduce risk.
• Infectious viruses (e.g., Epstein-Barr virus, Parvovirus B), bacteria (e.g., Salmonella spp., Shigella spp.) have been linked to the development of JIA, in addition, vaccinations, antibiotics, vitamin D deficiency, stress, and trauma may be causal factors.
• Gastrointestinal infections that result in reduced diversity in the gut microbiome and disturbances in tryptophan metabolism can elevate the susceptibility to developing enthesitis-related arthritis (ERA).

Epidemiology

JIA is the most common chronic heterogenous rheumatologic condition in children. It is estimated that around 3 million children and young adults have JIA. The global prevalence is believed to range from 3.8 to 400/100,000; the incidence is estimated to be 1.6 to 23/100,000.

• Females are at higher risk of JIA than males
• The oligoarticular subtype is more common

Characteristics and Clinical Presentation

Anterior-uveitis

Symptoms of JIA vary depending on the type of arthritis. It has an unpredictable course - it can be self-limiting or cause joint damage. But there is a general pattern of inflammatory joint disease in one or more joints:

• Synovitis
• Joint effusion
• Swelling of soft tissues
• Osteopenia
• Bone oedema, erosions

Certain features of JIA will depend on the age of the child affected (e.g. involvement of epiphyseal growth plates, early physeal fusion or the development of discrepancies in limb length).

Individuals may also experience:

• Pain and stiffness, including morning stiffness
• Fatigue

• Fever
• Skin rash
• Generally feeling unwell (malaise)
• Uveitis (see image)
• Decreased range of motion and soft tissue contractures
• Muscle atrophy
• Weakness, or reduced muscular endurance
• Gait deviations

Diagnostic Tests

There is no definitive test to diagnose JIA, so JIA is a diagnosis based on exclusion. The following evaluations are often included:

• Medical history
• Physical examination
• Laboratory tests - typical inflammatory markers are said to be common, particularly in oligoarthritis
• Imaging
  • Radiography for symptomatic joints (in early JIA, there are no detectable changes on x-ray, but indirect signs may be present, increased soft tissue density etc)
  • Ultrasound
  • MRI (the gold standard)
• Eye examination

Pathology

Figure.2 Prevalence of Major Subtypes of JIA

There are several subtypes of JIA:

1. Oligoarticular JIA (also known as pauciarticular)
   • affects four or fewer joints in the first six months of disease
   • peak age for oligoarticular JIA is 1-6 years
   • more common in females
   • tends to impact medium and large joints
   • risk of uveitis
2. Polyarticular JIA
   • affects more than 5 joints
   • peak ages for polyarticular JIA are 1-4 years and 7-10 years
   • more common in females
   • tends to impact small and medium joints
3. Systemic onset JIA
   • also known as Still's disease
   • associated with fever, other signs of systemic inflammation and arthritis
   • arthritis may begin weeks / months after the initial symptoms
   • affects females / males equally
4. Psoriatic JIA
   • causes psoriasis and inflammatory arthritis (these can develop at different times)
   • more common in females
   • occurs in preschool-aged children and at around 10 years
   • tends to impact fingers, wrists, toes, but not exclusively
5. Enthesitis-related JIA
   • inflammation of entheses
   • more common in males
   • tends to occur in older children / adolescents
   • association with acute uveitis
6. Undifferentiated JIA
   • JIA that does not fit into another category

Differential Diagnosis

Conditions that might be considered in a differential diagnosis include:

• Lyme Disease
• Rheumatic fever
• Osteomyelitis
• Psoriatic arthritis
• Inflammatory bowel disease
• Leukemia
• Caffey Disease
• Chronic Eosinophilic Granuloma
• Osteoporosis
• Involutional Osteoarthritis

Management

Pharmacology

The choice of medication depends on type and severity of JIA and if there are other conditions present. Common medications include analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, disease modifying anti-rheumatic medications, biologics and biosimilar medicines and eye drops.

Physiotherapy Management

Physiotherapy interventions focus on maintaining joint function and strength and teaching joint preservation strategies. Exercise programmes should incorporate low-impact, weight-bearing exercises (e.g. aquatic or bike programmes, gentle resistance exercises).

Rehabilitation might include:

• strengthening
• range of motion exercises and stretching
• education on joint protection and pain reducing techniques
• home exercise programme
• muscle relaxation techniques
• splints / orthotics to help maintain bone and joint alignment / prevent deformities
• adaptive equipment

Some modalities that might be used to help symptoms such as pain include:

• ultrasound
• paraffin wax dips (primarily for hands and feet)
• moist compress (hot packs)
• hydrotherapy
• cold packs