Differential Diagnosis
- Single most likely diagnosis
- Systemic lupus erythematosus (SLE): The patient's symptoms, including recurrent fever, chest pain that worsens with inhalation or lying flat (suggestive of pericarditis), joint pain, and the presence of a friction rub along the left sternal border, are consistent with SLE. The elevated erythrocyte sedimentation rate (ESR) and antinuclear antibody (ANA) titer of 1:640 further support this diagnosis. The patient's photograph is mentioned, which might imply a characteristic butterfly rash often seen in SLE, though not explicitly described.
- Other Likely diagnoses
- Juvenile arthritis: Given the patient's history of intermittent moderate pain in the elbows and knees, juvenile arthritis could be considered. However, the presence of systemic symptoms like fever, chest pain suggestive of pericarditis, and significant laboratory findings (elevated ESR and positive ANA) lean more towards SLE.
- Pericarditis due to other causes: The patient has pericarditis, which could be due to various causes including viral infections, but the combination of symptoms and laboratory findings points more specifically towards an autoimmune cause like SLE.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Acute rheumatic fever: Although the patient does not have a sore throat, acute rheumatic fever can present with carditis (including pericarditis) and arthritis. The elevated Antistreptolysin O titer (ASO) could suggest recent streptococcal infection, but the clinical context and other laboratory findings make SLE more likely.
- Kawasaki disease: This condition can cause fever, rash, and cardiac complications but typically presents in younger children. The absence of other classic Kawasaki disease symptoms (e.g., bilateral nonexudative conjunctivitis, erythema of the oral and pharyngeal mucosa, changes in the extremities) makes it less likely.
- Rare diagnoses
- Mucocutaneous lymph node syndrome (Kawasaki disease): As mentioned, while possible, it's less likely due to the patient's age and the absence of characteristic symptoms.
- Erythema infectiosum (fifth disease) and Rubella: These conditions can cause rash and fever but do not typically cause pericarditis or significant joint pain as described. They are less likely given the patient's symptoms and laboratory findings.
- Scarlet fever: This condition can cause fever and rash but is typically associated with a sore throat and exudative pharyngitis, which the patient does not have.
- Measles: Given the patient's symptoms and the lack of mention of a rash characteristic of measles or respiratory symptoms, this is unlikely.