Table 2

Differential diagnosis of the rash and musculoskeletal symptoms considered at morning ward round

Differential diagnosisFactors supporting this diagnosisFactors not supporting this diagnosis
Rheumatic diseases
Pauciarticular juvenile idiopathic arthritis (JIA)Lymphadenopathy is sometimes present in JIAThe 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 erythematosisFeverArthralgia that is not episodic
No malar rash
Kawasaki diseaseFever, rash (although not polymorphic) and lymphadenopathyNo stomatitis
No conjunctivitis
Fever duration <5 days
Serum sicknessAcute onsetNo recent medications
FeverRash not urticarial
Henoch-Schlonlein purpuraRash not purpuric
High fever unusual
Bacterial infection
Septic arthritisElevated ESR, C-reactive proteinUltrasound normal, blood culture negative (but only positive in 30% of cases)
OsteomyelitisElevated 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
RubellaMMR vaccine up to date
Rash not typical
Parvovirus B19Arthralgia 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 virusesNever had a blood transfusionMay get arthritis with hepatitis B
Rheumatic feverMay 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 arthritisNo history of sore throat, no hepatosplenomegaly, no diarrhoea, no compatible rash
Acute leukaemiaNo haematological abnormalities