Juvenile Spondyloarthritis

The juvenile spondyloarthritis is a group of HLA- B27 associated disorders which includes juvenile ankylosingspondylitiss and others. These are similar to adult spondyloarthropathies and juvenile onset means that these start before age 16.

In the adult form, inflammatory low back pain is the predominant clinical symptom but the juvenile onset spondyloarthritis has peripheral enthesitis and arthritis, predominantly of the lower extremities as its main clinical features.

Due tothe overlapping presentation and low sensitivity of x-rays to detect early changes in the children, the diagnosis making is difficult in these cases.

Prevalence of juvenile spondyloarthritis range from 1-4 per 1,000 children

Classification of Juenile Spondyloarthritis

There are two classification criteria used.

Juvenile spondyloarthritides is classified as the enthesitis-related arthritis subgroup of juvenile idiopathic arthritis from the International League of Associations for Rheumatology (ILAR).

They are also part of the European Spondyloarthropathy Study Group (ESSG) classification criteria as is used in adults.

ILAR Criteria

Patients are said to have enthesitis-related arthritis if they have arthritis or enthesitis  and two of the following

• Sacroiliac joint tenderness [either at time of presentation or in history]
• Inflammatory lumbosacral back pain
• Presence of HLA-B27 antigen
• Arthritis in a male patient older than 6 years of age
• Acute anterior uveitis
• A first degree relative with a history of
  • Ankylosing spondylitis
  • Enthesitis-related arthritis
  • Sacroiliitis with inflammatory bowel disease
  • Reactive arthritis
  • Acute anterior uveitis

Exclusion criteria

Enthesitis-related arthritis is rare if the following are present

• Psoriasis or history of psoriasis in the patient or first-degree relative
• Presence of IgM rheumatoid factor on at least two occasions 3 months apart
• Presence of systemic juvenile idiopathic arthritis

The ESSG criteria

Presence of inflammatory back pain or synovitis in addition to one of the following

• Family history
• Psoriasis
• Inflammatory bowel disease
• Urethritis
• Cervicitis
• Acute diarrhea
• Alternating buttock pain
• Enthesopathy
• Sacroiliitis

There are no exclusions in this criteria.

Further, it must be noted that ESSG criteria is inclusive of psoriatic arthritis, reactive arthritis and inflammatory disease which are part of exclusion criteria by the ILAR classification criteria.

ILAR classification is mostly used.

Most children with juvenile spondyloarthritis fall into the categories of enthesitis-related arthritis, psoriatic arthritis, and undifferentiated arthritis.

Children with psoriatic arthritis have arthritis and psoriasis or arthritis plus a minimum of 2 of the following

• Nail pitting or onycholysis
• Dactylitis – sausage-like swelling of the fingers or toes
• A parent with psoriasis.

Children who do not fulfill any of the juvenile spondyloarthritis or juvenile idiopathic arthritis fall into the category of undifferentiated spondyloarthropathy.

Juvenile ankylosing spondylitis, reactive arthritis, and inflammatory-bowel-disease-associated arthritis but that are traditionally thought of as juvenile spondyloarthritis [These are not accounted for in the ILAR classification]

Clinical Manifestations of Juvenile Spondyloarthritis

In juvenile spondyloarthritis, enthesitis and peripheral arthritis is the main feature as compared to adult counterparts where the back pain is a major feature.

The joints involved mainly and typically are of the lower limb. The joints show an asymmetric involvement. The presence of hip arthritis and arthritis of the small joints of the midfoot are highly suggestive of the diagnosis.

Symptoms of back pain can also be present when the spine is involved.

The clinical course of the arthritis is variable from a single episode of monoarthritis that resolves to the development of a destructive symmetric polyarthritis with joint destruction.

Eye pain can occur due to acute anterior uveitis in about 25% of the cases. Cardiac involvement like conduction disease, valvular disease, and pulmonary involvement are less common.

Diagnosis

The definitive diagnosis is still made using the modified New York criteria. It relies on X-ray findings of sacroiliitis by plain radiography. But X-ray changes appear quite late after the first symptoms appear.

MRI  has increased sensitivity for sacroiliitis.

Management and Treatment

Methotrexate and sulfasalazine are two commonly used drugs that have established efficacy for peripheral arthritis in children. Another drug that has recently been added is anti-tumor necrosis factor (anti-TNF) medications.

Anti-TNF medications are effective in lower back arthritis also.

Ustekinumab, secukinumab, and apremilast are not yet evaluated in the children.

Prognosis of  Juvenile Spondyloarthritis

Females with juvenile ankylosing spondylitis were found to have better health scores than those with other arthritis subtypes after 7 years.

Hip joint involvement appears to be closely related to a poorer prognosis.

50-75% patients with undifferentiated spondyloarthropathy progress to ankylosing spondylitis.