Differential Diagnosis

The patient presents with a complex array of symptoms including fever, sore throat, dry cough, weakness, headache, sleep disturbance, muscle and joint pain, icteric sclera, and an abundant rash on the trunk. Considering these symptoms and the epidemiological history, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Infectious Mononucleosis: This diagnosis is highly likely due to the combination of symptoms such as fever, sore throat, lymphadenopathy (enlargement of lymph nodes), splenomegaly (enlargement of the spleen), and a rash, which are all characteristic of infectious mononucleosis caused by Epstein-Barr virus (EBV). The presence of a spotty-papular rash, especially after the administration of ampicillin, further supports this diagnosis, as it is a known reaction in patients with EBV infection.

• Other Likely Diagnoses

  • Enterovirus Infection: While less specific, enterovirus infections can cause a wide range of symptoms including fever, rash, and sore throat. However, the presence of splenomegaly and the specific pattern of the rash might make this diagnosis less likely compared to infectious mononucleosis.
  • Herpetic Tonsillitis: This could explain the sore throat and fever but would not typically account for the rash, lymphadenopathy, or splenomegaly.
  • Yersiniosis: This bacterial infection can cause fever, abdominal pain, and sometimes a rash, but the overall clinical picture, including the specific symptoms and the absence of prominent gastrointestinal symptoms, makes it less likely.

• Do Not Miss Diagnoses

  • Brucellosis: Although less common and not directly suggested by the symptoms, brucellosis can cause fever, weakness, and lymphadenopathy. It's a zoonotic infection that could be considered in individuals with exposure to animals or their products. Missing this diagnosis could lead to significant morbidity due to its potential to cause chronic infection and complications if not treated properly.
  • Hepatitis: The presence of icteric sclera (yellowing of the eyes) suggests liver involvement, which could be due to viral hepatitis. This diagnosis is critical not to miss due to the potential for severe liver disease and the need for specific management.

• Rare Diagnoses

  • Other Viral Hemorrhagic Fevers or Rickettsial Diseases: These could present with fever, rash, and systemic symptoms but are less likely given the epidemiological context and the specific constellation of symptoms.
  • Autoimmune or Connective Tissue Diseases: Conditions like systemic lupus erythematosus (SLE) can present with a wide range of symptoms including rash, fever, and joint pain. However, the acute onset and specific pattern of symptoms in this case make these diagnoses less likely.