Differential Diagnosis for a 5-year-old boy with fever and knee pain
- Single most likely diagnosis
- Acute Rheumatic Fever (ARF): The patient's recent history of streptococcal pharyngitis, followed by the development of fever, joint pain (particularly affecting the knee), and elevated inflammatory markers (CRP and ESR), are consistent with ARF. The condition is known to occur after a streptococcal infection, and the patient's symptoms align with the Jones criteria for ARF diagnosis.
- Other Likely diagnoses
- Septic Arthritis: The presence of fever, joint effusion, and significant pain with movement of the affected knee, along with elevated leukocytes and inflammatory markers, could suggest septic arthritis, especially if the joint aspirate shows evidence of infection.
- Juvenile Idiopathic Arthritis (JIA): Although less likely given the acute onset and recent streptococcal infection, JIA could be considered, particularly if the patient does not meet the full criteria for ARF or if symptoms persist beyond the expected timeframe for ARF.
- Post-streptococcal Reactive Arthritis (PSRA): This condition is similar to ARF but does not meet the full Jones criteria. It could be considered if the patient's symptoms are primarily limited to arthritis without significant cardiac or neurological involvement.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Osteomyelitis: Although the primary presentation is of joint involvement, osteomyelitis (infection of the bone) could present similarly and requires prompt diagnosis and treatment to prevent serious complications.
- Lyme Arthritis: If the patient lives in an area endemic for Lyme disease, this should be considered, especially if there's a history of tick exposure. Lyme arthritis can cause knee pain and swelling, often accompanied by fever.
- Malignancy (e.g., Leukemia): While rare, malignancies can present with joint pain, fever, and fatigue. A high index of suspicion is necessary, especially if the patient's condition does not respond as expected to treatment for more common conditions.
- Rare diagnoses
- Kawasaki Disease: This condition can cause fever, joint pain, and inflammation but is typically associated with other specific criteria such as rash, conjunctivitis, and changes to the lips and oral cavity.
- Henoch-Schönlein Purpura (HSP): A form of vasculitis that can cause joint pain, fever, and rash, particularly on the lower extremities. It's less likely given the patient's presentation but should be considered if other symptoms such as abdominal pain or rash develop.