Classification

Definition

 

JRA / JCA

- heterogenous inflammatory joint disease

- °infective aetiology 

- > 3/12 duration & < 16 years old

 

Systemic / Pauciarticular / Polyarticular

 

Epidemiology

 

1: 10000

- M = F

- Different subgroups have associated with different HLA types

 

Aetiology

 

Unknown

- ?  Immune aberration to infectious agent

- Similar to RA

- Genetic predisposition

 

Classification

 

Must be > 6/52

Classify after 6/12

 

1. Systemic JCA 

- Still's disease

- fever, rash, lymph nodes, hepatosplenomegaly

- 20%

- poorest long term prognosis

 

2. Pauciarticular JCA 

- < 4 joints

- 30%

 

Divided into

A. Early onset < 6

- ANA

- F > M

B. Late onset

- like Ankylosing Spondylitis / HLA B27

- M > F

 

3. Polyarticular JCA >5 joints

- 60%

- most common

 

Divided into

A.  Seronegative

B.  Seropositive

- more severe with joint destruction

 

Systemic / Still's Disease

 

Epidemiology

 

Usually < 3 years old

- M = F 

- usually not ANA or RF +ve

 

Systemic symptoms

 

Febrile ~ 40°

Maculopapular rash 

Malaise

Nodes

Hepatosplenomegaly

Joint symptoms occur weeks after onset

 

Joints

 

Initially mild swelling & pain

- may progress to Polyarthritis

- commonly Knee / Wrists / Ankle & Midfoot

- flexor Tenosynovitis

- MCPJ & PIPJ swelling

 

Usually resolves with systemic illness

- long term affects hips and cervical spine

 

Rash

 

Fluctuates with the fever 

- may only appear at night or in evening 

- i.e. not when seen in clinic

- salmon pink

 

Investigations

 

ESR ~ 100

Increased WCC + Neutrophilia

Mild Anaemia

Increased IgG

RF negatgive

Increased CD4 T Cells

 

Prognosis

 

Children almost always get spontaneous resolution of disease as teenager

- left with degenerative joints

- moderate to severe arthritis in ~ 50% 

- frequent involvement of hips

 

Stunted growth 

- steroids make stunting even worse

 

Pauciarticular

 

Very typical case presents with monoarticular arthritis of knee

- < 5 joints in 1st 3/12 

- no Stills symptoms

 

A. Early onset / 50 - 60% ANA Positive

 

Present

- <6 years 

- F>M

 

Medium joints

- Knee / AJ / Elbow

- Flexor Tenosynovitis

- PIPJ 

 

Chronic Iridocyclitis

- 50%

- resolves after few years

- follow up until late teens for eyes

 

B Late onset / Positive HLA B27

 

Present

- > 9 years

- M > F 

- positive FHx

- RF negative

 

Most develop Sacroiliitis & Spondylitis

 

LL affected 

- KJ / AJ / Hip

 

Enthesitis

- Plantar Fascia / TA / Tib Tubercle

 

Iritis

- commonest cause of blindness in western world 

- can be treated with steroids 

- must all see ophthalmologist every 3 months until 20 years old even if in remission

 

Overall excellent prognosis 

- minimal drug treatment required

- Main problem is actually the iritis

 

Polyarticular

 

Present

- > 5 joints within first 3/12 

- F > M 

- ANA positive in 50%

- symmetrical polyarthritis

- small & large joints

 

A. Seronegative

 

More common 

- 85% of polyarticular

 

Affects KJ most commonly

- wrists / ankle / C spine

- flexor tenosynovitis

- 1st MTPJ

 

B. Seropositive / Juvenile RA

 

Older girls

- Small joints of hands & feet

- nodules

- +ve RF

 

Rapidly progressive with joint destruction

- more likely to be persistent into adulthood

 

X-ray

- non-specific changes early

- have severe periarticular osteopenia

- later joint erosion & deformity