Rheumatic diseases
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Pauciarticular juvenile idiopathic arthritis (JIA) | Lymphadenopathy is sometimes present in JIA | The diagnosis of JIA is based on the physical finding of arthritis (or synovitis) in at least one joint that persists for at least 6 weeks, with other causes being excluded. Typically knees ankles and wrists are affected Rash is “salmon pink” There is often hepatosplenomegaly in JIA |
| Elevated ESR | |
Systemic lupus erythematosis | Fever | Arthralgia that is not episodic |
| | No malar rash |
Vasculitis
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Kawasaki disease | Fever, rash (although not polymorphic) and lymphadenopathy | No stomatitis |
| | No conjunctivitis |
| | Fever duration <5 days |
Serum sickness | Acute onset | No recent medications |
| Fever | Rash not urticarial |
Henoch-Schlonlein purpura | | Rash not purpuric |
| | High fever unusual |
Bacterial infection
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Septic arthritis | Elevated ESR, C-reactive protein | Ultrasound normal, blood culture negative (but only positive in 30% of cases) |
Osteomyelitis | Elevated ESR in 90% | Ultrasound not showing elevation of the periosteum (may be seen in experienced hands within the first week) |
| Elevated CRP in 98% | ?need for bone scan to exclude this diagnosis but no bony tenderness noted |
| (Normal x ray compatible as x ray remains normal until >50% bone has been demineralised) | |
Viral infection
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Rubella | | MMR vaccine up to date |
| | Rash not typical |
Parvovirus B19 | | Arthralgia usually symmetric, involving hands, wrists, knees, and feet; arthralgia not symmetrical in this case Erythema infectiosum (fifth disease) characterised by a erythematous malar rash (slapped cheek) and a reticulated lace like rash on the extremities |
| | Rash not typical |
| | Fever did not resolve when rash appeared |
Hepatitis viruses | Never had a blood transfusion | May get arthritis with hepatitis B |
Post-infectious
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Rheumatic fever | May have some minor criteria—fever, arthralgia, and raised acute-phase reactants. Perhaps the rash is erythema marginatum? | No carditis |
| | No chorea |
| | No subcutaneous nodules |
| | No polyarthritis |
Reactive arthritis | | No history of sore throat, no hepatosplenomegaly, no diarrhoea, no compatible rash |
Neoplastic
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Acute leukaemia | | No haematological abnormalities |