Differential diagnosis of the rash and musculoskeletal symptoms considered at morning ward round
| Differential diagnosis | Factors supporting this diagnosis | Factors not supporting this diagnosis |
|---|---|---|
| Rheumatic diseases | ||
| 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 | ||
| 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 | ||
| 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 | ||
| 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 | ||
| 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 | ||
| Acute leukaemia | No haematological abnormalities | |