Differential Diagnosis
- Single most likely diagnosis
- Serum sickness-like reaction (SSLR): This is the most likely diagnosis given the patient's recent history of amoxicillin-clavulanate use, which is a common cause of SSLR. The symptoms of joint pain, pruritic rash, and generalized lymphadenopathy are consistent with this diagnosis.
- Other Likely diagnoses
- Viral exanthem: The patient's symptoms of rash, fever, and lymphadenopathy could be consistent with a viral exanthem, such as a viral rash caused by a common childhood illness.
- Allergic reaction: The patient's rash and joint pain could be due to an allergic reaction to another medication or substance, although the recent use of amoxicillin-clavulanate makes SSLR more likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN): Although the patient's rash is described as blanchable and urticarial, it is essential to consider SJS or TEN, which can be life-threatening and require prompt treatment. The absence of target lesions and oral mucosal involvement makes this less likely, but it should not be entirely ruled out.
- Juvenile idiopathic arthritis (JIA): While the patient's joint pain and fever could be consistent with JIA, the recent history of antibiotic use and the presence of a rash make SSLR more likely. However, JIA can be a serious condition and should be considered in the differential diagnosis.
- Rare diagnoses
- Kawasaki disease: This condition is characterized by fever, rash, and lymphadenopathy, but it typically presents with more specific criteria, such as bilateral conjunctival injection and changes in the lips and oral mucosa, which are not present in this patient.
- Autoimmune disorders (e.g., systemic lupus erythematosus): While these conditions can present with joint pain, rash, and fever, they are less likely given the patient's age and the recent history of antibiotic use. However, they should be considered in the differential diagnosis if the patient's symptoms persist or worsen over time.