Differential Diagnosis
The patient's symptoms and reaction to amoxicillin suggest an infectious etiology, potentially complicated by an allergic reaction or a specific disease process. The following differential diagnoses are considered:
Single most likely diagnosis
- Infectious mononucleosis (IMN) caused by Epstein-Barr virus (EBV): The patient's symptoms of malaise, anorexia, fever, sore throat, bilateral cervical lymphadenopathy, and palatal petechiae are classic for IMN. The rash that developed after amoxicillin treatment is also a known phenomenon in patients with IMN, as they are more likely to experience a drug rash.
Other Likely diagnoses
- Streptococcal pharyngitis: Although the patient was treated with amoxicillin, which is effective against streptococcal infections, the development of a rash and lymphadenopathy could suggest a more complex infection or an allergic reaction. However, streptococcal infections can sometimes present with lymphadenopathy.
- Acute viral pharyngitis: Other viruses could cause similar symptoms, and the reaction to amoxicillin might be coincidental or indicative of a viral etiology that does not respond to antibiotics.
- Allergic reaction to amoxicillin: While the symptoms could suggest an allergic reaction, the presence of lymphadenopathy and palatal petechiae points more towards an infectious process.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Lemierre's syndrome: A rare but potentially life-threatening condition characterized by pharyngitis followed by cervical lymphadenopathy and sepsis, typically due to Fusobacterium necrophorum. Although less likely, it's critical to consider due to its severity.
- HIV infection: Acute HIV infection can present with similar symptoms, including fever, sore throat, and lymphadenopathy. The rash could be part of the acute retroviral syndrome.
- Toxoplasmosis: In immunocompetent individuals, toxoplasmosis can cause lymphadenopathy and sometimes a sore throat, although it's less common.
Rare diagnoses
- Cytomegalovirus (CMV) infection: CMV can cause a mononucleosis-like syndrome, especially in immunocompromised patients, but it's less common in immunocompetent individuals.
- Toxoplasmic lymphadenitis: A rare condition where Toxoplasma gondii infects the lymph nodes, potentially causing lymphadenopathy.
- Lymphoma: Although extremely rare as a initial presentation with these exact symptoms, lymphoma can cause lymphadenopathy and systemic symptoms like fever and malaise.