Differential Diagnosis

The patient's presentation is complex, involving initial symptoms suggestive of a bacterial infection (strep throat) followed by neurological symptoms and significant lymphadenopathy along with hepatosplenomegaly. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Infectious Mononucleosis (IMN) due to Epstein-Barr Virus (EBV): The patient's symptoms, including sore throat, fever, weakness, lymphadenopathy, and hepatosplenomegaly, are classic for IMN. The recent treatment for strep throat could be coincidental or EBV infection might have been misdiagnosed as strep throat initially. The neurological symptoms could be part of the spectrum of EBV infection, which can cause a range of neurological manifestations.

• Other Likely Diagnoses

  • Lymphoma: Given the widespread lymphadenopathy and hepatosplenomegaly, lymphoma is a consideration, especially in an elderly patient. However, the acute presentation with fever and sore throat is less typical.
  • Toxoplasmosis: This infection can cause lymphadenopathy and, in immunocompromised patients, more severe symptoms including neurological manifestations. However, the hepatosplenomegaly and the specific sequence of symptoms are less typical.
  • Cytomegalovirus (CMV) Infection: CMV can cause a mononucleosis-like syndrome with fever, lymphadenopathy, and hepatosplenomegaly, similar to EBV. It's more common in immunocompromised individuals but can occur in immunocompetent individuals as well.

• Do Not Miss Diagnoses

  • Meningitis or Encephalitis: The patient's symptoms of vomiting, photophobia, and neurological deficits (weakness, numbness, tingling) could indicate meningitis or encephalitis, which are medical emergencies requiring prompt diagnosis and treatment.
  • Stroke or Transient Ischemic Attack (TIA): Although less likely given the patient's age and the presence of systemic symptoms, a stroke or TIA could explain the sudden onset of weakness and numbness. The absence of typical risk factors or a clear vascular distribution might lower the suspicion, but these conditions are always a "do not miss" due to their urgency.
  • Hematological Malignancies (e.g., Leukemia): These can present with hepatosplenomegaly, lymphadenopathy, and systemic symptoms. A diagnosis of leukemia would be critical to establish promptly due to its implications for treatment and prognosis.

• Rare Diagnoses

  • Cat-Scratch Disease: Caused by Bartonella henselae, this infection can lead to lymphadenopathy and, in rare cases, more severe systemic symptoms including neurological manifestations.
  • Brucellosis: A zoonotic infection that can cause fever, lymphadenopathy, and hepatosplenomegaly, along with a variety of other symptoms depending on the organ systems involved.
  • Histoplasmosis: A fungal infection that can cause a range of symptoms from mild respiratory illness to severe disseminated disease with lymphadenopathy and hepatosplenomegaly, particularly in immunocompromised individuals.