Differential Diagnosis for a 10-year-old with Sore Throat, Rash after Amoxicillin, Positive Mono Test, and Negative EBV IgM
- Single Most Likely Diagnosis
- Infectious Mononucleosis (Mono) due to Epstein-Barr Virus (EBV): The positive mono test strongly suggests this diagnosis. Although the EBV IgM is negative, it's possible that the test was done too early or too late in the course of the illness, or the patient may have had a false-negative result. The rash after amoxicillin is a common occurrence in patients with mono.
- Other Likely Diagnoses
- Allergic Reaction to Amoxicillin: The development of a rash after taking amoxicillin could indicate an allergic reaction. However, the presence of a sore throat and a positive mono test suggest that the rash might be related to the underlying infection rather than a simple allergic reaction.
- Cytomegalovirus (CMV) Infection: CMV can cause a mononucleosis-like syndrome, but the positive mono test and the clinical presentation make EBV more likely. CMV infection would typically require specific testing for diagnosis.
- Do Not Miss Diagnoses
- Streptococcal Pharyngitis: Although the patient has a positive mono test, it's crucial to rule out streptococcal pharyngitis, especially if the sore throat is severe or if there are other symptoms like fever and swollen lymph nodes. A rapid streptococcal antigen test or throat culture should be considered.
- Acute Leukemia: Although rare, acute leukemia can present with sore throat, rash, and lymphadenopathy. The development of a rash after amoxicillin in this context could be misleading, and a thorough investigation, including blood counts and possibly a bone marrow biopsy, might be necessary if other signs or symptoms suggest leukemia.
- Rare Diagnoses
- Toxoplasmosis: This parasitic infection can cause a mononucleosis-like syndrome but is less common and would typically require specific serologic testing for diagnosis.
- Human Herpesvirus 6 (HHV-6) Infection: HHV-6 can cause roseola in young children but can also lead to a mononucleosis-like illness in older children and adults. However, this would be an uncommon cause of the patient's symptoms and would require specific testing for confirmation.