Differential Diagnosis of Fever with Joint Pain

Initial Diagnostic Framework

High-spiking quotidian fever (>39°C, late afternoon/evening peaks) strongly suggests Adult-Onset Still's Disease (AOSD), occurring in 95.7% of cases, according to the American College of Rheumatology 1, 2, 3
Fever duration >5 days with specific associated features raises concern for acute rheumatic fever (ARF), as stated by the American Heart Association 4, 5
Migratory polyarthritis affecting large joints is classic for ARF, though strict migratory pattern may not always be present, as noted by the American Heart Association 4
Symmetric polyarthritis with wrist, knee, and ankle involvement suggests AOSD, according to the American College of Rheumatology 1, 2, 3

Septic arthritis must be excluded in any monoarticular presentation with fever, as recommended by the Infectious Diseases Society of America 6
Bacterial infections, including endocarditis, particularly with new cardiac findings, should be considered, according to the American Heart Association 7
Viral syndromes typically resolve within 3 months, as stated by the American Academy of Pediatrics 8

The revised Jones Criteria require evidence of preceding Group A Streptococcal infection PLUS 2 major criteria OR 1 major + 2 minor criteria, as stated by the American Heart Association 4, 5
Major criteria include carditis, polyarthritis, chorea, erythema marginatum, and subcutaneous nodules, according to the American Heart Association 4, 5
Minor criteria include polyarthralgia, fever, elevated ESR or CRP, and prolonged PR interval on ECG, as noted by the American Heart Association 4, 5

The classic triad of high-spiking quotidian fever, evanescent salmon-pink maculopapular rash, and arthritis/arthralgia is 93.5% sensitive for AOSD, according to the American College of Rheumatology 1, 2, 3
Laboratory findings include marked leukocytosis, elevated ESR and CRP, and elevated ferritin with low glycosylated fraction, as stated by the American College of Rheumatology 1, 2, 8

Familial Mediterranean Fever is characterized by self-limited episodes of peritonitis, pleuritis, and acute monoarthritis, according to the European League Against Rheumatism 8
TRAPS is characterized by longer fever attacks, ocular involvement, and centrifugal erythematous patches, as noted by the European League Against Rheumatism 8

Mandatory first-line tests include complete blood count with differential, ESR and CRP, and blood cultures if septic arthritis is suspected, as recommended by the American College of Rheumatology 1, 2, 6
Second-line serologic testing includes ANA, rheumatoid factor, anti-CCP, and ferritin with glycosylated fraction, according to the American College of Rheumatology 1, 6, 8

Joint imaging includes plain radiographs to exclude metastases and evaluate for erosions, as recommended by the American College of Rheumatology 6
Wrist radiographs are specifically recommended in suspected AOSD, according to the American College of Rheumatology 1, 3
Echocardiography is mandatory if ARF is suspected, as stated by the American Heart Association 4, 5

Hold any immunosuppression and initiate empiric antibiotics immediately after cultures are obtained, as recommended by the Infectious Diseases Society of America 6
Urgent orthopedic consultation for drainage is necessary, according to the American Academy of Orthopaedic Surgeons 6

Anti-inflammatory therapy, such as aspirin or NSAIDs, is recommended for arthritis, as stated by the American Heart Association 6
Penicillin prophylaxis is necessary for secondary prevention, according to the American Heart Association 6

NSAIDs are recommended as first-line treatment for mild disease, as stated by the American College of Rheumatology 6
Corticosteroids, such as prednisone, are recommended for moderate-severe disease, according to the American College of Rheumatology 6
DMARDs, such as methotrexate, or biologics, such as IL-1 or IL-6 inhibitors, may be considered for refractory cases, as noted by the American College of Rheumatology 1, 8