Paediatrics: Systemic arthritis

Systemic arthritis

Multisystem disease is often diagnosed late as joint involvement is often late. Peak age 2–3yrs; 10–20% JIA; equal male:female.

Clinical features

•   Fever is essential, typically quotidian up to 39°C, returning to normal between attacks.

•   Rash: salmon pink, macular/urticarial on chest, trunk, and intertrigones. Present when warm and disappears within minutes.

•   Myalgia, arthralgia, and arthritis. Arthritis often appears after first 6mths of illness and can be oligo- or polyarthritis.

•   Generalized lymphadenopathy and hepatosplenomegaly.

•   Polyserositis with pericarditis, pleuritis, and sterile peritonitis. Silent pericardial effusions (15%). Myocarditis + tachycardia, cardiomegaly, and congestive cardiac failure is rare.

•   Growth retardation s to disease, steroids, or joint damage.

•   Late complications: amyloidosis (difficult to treat).

•   MAS: rare, life-threatening; precipitated by infection or NSAIDs. Haemophagocytic bone marrow with falling WBC, platelets, and ESR, and very high ferritin.

Investigations

•   FBC (normocytic or hypochromic anaemia; leucocytosis; thrombocytosis).

•   ESR/CRP can be high: use to monitor disease during treatment.

•   Hypoalbuminaemia: multifactorial—poor diet, general ill health with catabolism, possibly proteinuria secondary to renal amyloid.

•   ANA and RF usually –ve

•   Viral titres and blood cultures.

•   Malignancy screen: CXR, US abdomen.

•   ECG and echocardiogram.

Management

•   NSAIDs for initial management of pain, fever, and serositis. Indomethacin often used for pericarditis.

•   Pulsed IV corticosteroids if no improvement after 1wk of NSAIDs.

•   Oral steroids at 1mg/kg in divided doses until fever settled and inflammatory markers normal. Taper dose to reduce side-effects. Use alternate day doses and add steroid-sparing agent.

•   MTX is used, but is not as effective as in other JIA subsets.

•   Intra-articular corticosteroid for flares of single joints.

•   Biological therapy: anti-TNF and anti-IL6 in resistant cases.

Prognosis

Three groups—monocyclic (11%); recurrent or polycyclic (34%); and per-sistent (55%). Monocyclic patients do well. More than 33% of the others will have permanent disability with active disease in adult life. Death from infection, MAS, or amylodosis.