Dr Adam Truelove; Dr Jenny Pallawela

Emma is a paediatric trainee seeing patients in a busy paediatric rheumatology clinic. Her next patient is Amna, an 11-year-old girl, whose presenting complaint is only “swelling/joint pain” on the electronic patient record.

How would you approach this patient (or any general paediatric rheumatology patient?)

This goes without saying – start by taking a history and examining them!

History taking can be divided into articular and extra-articular

• Articular
  • How many and which joints are affected: mono- (1) vs oligo- (2-4) vs polyarticular (>4)
  • How are the joints affected: swelling, erythema, early-morning stiffness, limited range of movement, whether the pain is worse after or unrelated to activity
  • How long have the joints been affected for
  • Any history of limping (particularly in younger children) or restrictions on activity (such as an inability to participate in PE)
• Extra-articular
  • ‘Butterfly’ facial rash (especially in warm weather)
  • Photosensitivity
  • Raynaud’s phenomenon
  • Features of psoriasis (especially in flexors, umbilicus, and back of the ears)
  • Features of colitis
  • Fever of unexplained origin

For the examination, pGALS is a useful screening tool, but largely will require you to examine every joint! This can be difficult, especially in younger children, and will require parent and/or play specialist input to keep them amused. Follow the look / feel / move sequence, especially looking out for:

Joints: Finger swelling tends be more obvious, but elbows need pressing relatively firmly to detect swelling. Shoulders are difficult to palpate, and swelling can be subtle (be aware that many rotator cuff injuries can present with shoulder pain!)

Localised hip pain tends to be felt in the groin rather than outside of the hip – if the child is pointing to outside of the hip area, think MSK!

Loss of knee dimples is a relatively sensitive sign of swelling, but they may have normal flexion even in severe swelling, so loss of normal extension is what to look out for.

Compare to your own range of movement (provided you know you have a normal range of movement in your joints). Most under-eights have a degree of hypermobility of their elbows (past zero degrees) and knees (to zero degrees)

A lack of leg length discrepancy can show that there hasn’t been any chronic joint degeneration of the hip and knee and an absence of a fixed flexion deformity, but does not exclude arthritis on it’s own!

Measure from the ASIS to medial malleolus – Less than 0.5cm is normal, more than 1cm is abnormal

Amna has intermittent swelling in her wrists, knees, ankles, and metacarpophalangeal joints, and proximal interphalangeal joints (of her hands) bilaterally for the last 8 months. She reports feeling stiff in these joints when she first wakes up and after she has done PE at school, which she had put down to “growing pains”. She also reports an intermittent, sharp earache that’s worsened by chewing.

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On examination, there is swelling of her wrists bilaterally, and loss of dimples in her knees but no overt swelling of her knees bilaterally. Her wrist flexion is limited to 45 degrees bilaterally, and there is mild fixed flexion deformity at her metacarpophalangeal and proximal interphalangeal joints bilaterally. Her leg length differs by 0.3cm. 

You had just(!) been reading up on JIA and suspect that Amna might have this. What is JIA, what other specific questions should you ask, and what else should you look out for?

Woah, slow down, one question at a time!

JIA, or juvenile idiopathic arthritis, is a rather broad term for a collection of idiopathic (their cause is unknown) arthropathies that begin before the age of 16 (hence juvenile), and last longer than six weeks. It affects roughly one-in-a-thousand children, and the presentation varies considerably; because of this, it is divided into four main subtypes based on the presentation (age, pattern of joints affected, extra-articular manifestations) and lab results. 

If you are concerned about JIA, it’s worth asking some extra questions to help with this subtyping early (you’ll see why later). 

For the history and examination, ask and look for:

• Features of uveitis (eye pain, redness, photophobia, blurred vision) and which eye(s) are affected
  • A slit lamp examination (if trained, this is the gold standard)
  • Remember young children (who are the group that are most prone to uveitis) are generally unable to report eye symptoms and there should be a low threshold for referral to an ophthalmologist in suspected JIA
• Rheumatoid nodules – look especially on the elbows or Achilles’ tendons
• Fever (especially lasting more than 2 weeks)
• A migrating, transient, salmon-pink rash that may exhibit Koebner phenomenon features (appearing after scratching or a hot bath)
• Any chest/abdominal pain (looking for serositis)

Amna has no conjunctival injection and reports no eye pain or headaches. There is no history or evidence of a salmon-pink rash or serositis, but you do notice a small, mobile, non-tender nodule on each of her Achilles’ tendons.

What subtype of JIA are you suspecting? What investigations need to be requested?

Three of the main four JIA subtypes are largely confined to the joints and are divided accordingly: oligoarticular (4 or fewer joints within six months of disease onset) vs the two polyarticular JIA subtypes (5 or more joints). Polyarticular JIA is subgrouped based on whether the rheumatoid factor is positive (seropositive JIA) or negative (seronegative JIA); this is because although treatment is largely the same, the joint pattern and the chance of remission are rather different. 

These are summarised in the table below.

The fourth main subtype is systemic-onset JIA, or juvenile Still’s disease as it closely resembles adult-onset Still’s disease. It classically has a triad of two weeks of fever, arthritis, and a salmon-pink rash (or less classically lymphadenopathy, splenomegaly/hepatomegaly, or serositis), together with high acute phase reactants (especially ferritin), leukocytosis, and anaemia.

For investigations, it is a fine line to walk between investigating adequately and requesting every test under the sun! That being said, here are some of the important ones not to forget

• Full blood count
• CRP and ESR (often not raised, especially if there is only one joint involved)
• LFTs and U&Es (if only to prove that they are normal)
• Creatine Kinase (exclude dermatomyositis)
• ANA (for extra-articular manifestations of JIA) and RF (especially if it’s polyarticular)
• Coeliac serology (useful for excluding enthesitis-related arthritides)
• Imaging of joints (plain X-rays are not helpful): USS (can show synovitis and/or joint effusions); MRI (helpful but technically difficult without sedation in younger children)

Type of JIA	Oligoarticular	Sero- polyarticular	Sero+ polyarticular	Systemic (Still’s disease)
Relative frequency	50%	30%	<10%	<10%
Peak incidence/year	2-3	1-4, 6-12 (bimodal)	9-12	2-4
Sex	F>M (3:1)	F>M	F>M (10:1)	F=M
Definition	≤4 joints within 6/12 of disease onset	≥5 joints within 6/12 of disease onset	Arthritis involving ≥1 joint AND ≥2/52 fever with spikes on ≥3/7 consecutively AND ≥1 extra-articular manifestation
Pattern	Asymmetric Large, weight-bearing joints	Often asymmetric Small and large joints Cervical spine and TMJ also affected	Symmetric Small and large joints	Normally affects ≥2 joints (but any pattern possible). Often affects knees, ankles, and wrists
Extra -articular manifestations	Bilateral chronic anterior uveitis	Unilateral painless anterior uveitis (especially if ANA negative)	Rheumatoid nodules	Salmon-pink rash Lymphadenopathy Spleno/hepatomegaly Serositis
Labs	Raised ESR RF negative ANA+ (70%)	Raised ESR RF negative ANA+ (40%)	Raised ESR RF positive (2 tests, more than 3 months apart)	Raised ESR, CRP, ferritin Anaemia, leukocytosis, thrombocytosis RF negative
Treatment	NSAIDs +/- intra-articular steroids (often end up on MTX)	NSAIDs + MTX	NSAIDs + MTX	NSAIDs
Chance of recurrence	Low	Variable	High	Variable

Based on her symmetrical polyarticular arthritis with rheumatoid nodules, you suspect Amna might have seropositive polyarticular JIA. Her blood tests confirm this, with a raised ESR (22), slightly raised CRP (5) and a positive RF. She is started on NSAIDs and methotrexate and makes a good improvement.

Key points

• JIA is a collection of arthritides with joint swelling and/or loss of range of movement lasting more than 6 weeks
• Remember! JIA is a diagnosis of exclusion (think about reactive arthritis, infection, and malignancy)
• A thorough history and examination will often lead you most of the way to the diagnosis before you reach for the (still important!) immunology tests, but it is ultimately a clinical diagnosis
• Think about systemic JIA in pyrexia of unknown origins
• Early referral for eye examination is essential in all cases of suspected JIA

Authors: Dr Adam Truelove, Paediatric SHO, Oxford University Hospitals; senior reviewer Dr Jenny Pallawela, Paediatric Consultant with special interest in paediatric rheumatology, North Middlesex Hospital