Differential Diagnosis for Infectious Mononucleosis

When considering a diagnosis of infectious mononucleosis, it's crucial to evaluate other potential causes of similar symptoms to ensure accurate diagnosis and treatment. The differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis
  • Streptococcal Pharyngitis: This condition often presents with sore throat, fever, and lymphadenopathy, similar to infectious mononucleosis. A throat culture or rapid streptococcal antigen test can help differentiate it.
• Other Likely Diagnoses
  • Acute Viral Pharyngitis: Caused by various viruses, it can mimic the symptoms of infectious mononucleosis but typically lacks the significant lymphadenopathy and splenomegaly.
  • Toxoplasmosis: Infection with Toxoplasma gondii can cause a mononucleosis-like syndrome, especially in immunocompromised individuals.
  • Cytomegalovirus (CMV) Infection: CMV can cause a syndrome similar to infectious mononucleosis, including fever, fatigue, and lymphadenopathy, particularly in young adults.
• Do Not Miss Diagnoses
  • Hodgkin Lymphoma: Although less common, it can present with lymphadenopathy, fever, and fatigue, similar to infectious mononucleosis. Missing this diagnosis could have severe consequences.
  • Leukemia: Certain types of leukemia, such as acute lymphoblastic leukemia (ALL), can present with symptoms overlapping those of infectious mononucleosis, including lymphadenopathy and splenomegaly.
  • AIDS (Acquired Immunodeficiency Syndrome): The acute retroviral syndrome of HIV infection can mimic infectious mononucleosis, making it a critical diagnosis not to miss due to its significant implications for patient management and public health.
• Rare Diagnoses
  • Brucellosis: A zoonotic infection that can cause fever, fatigue, and lymphadenopathy, although it is less common and typically associated with specific occupational exposures.
  • Cat-Scratch Disease: Caused by Bartonella henselae, it can lead to lymphadenopathy and systemic symptoms, but it is usually associated with a history of cat scratch or bite.
  • Yersinia enterocolitica Infection: This bacterial infection can cause a syndrome that includes fever, abdominal pain, and lymphadenopathy, which might be confused with infectious mononucleosis in some cases.

Each of these diagnoses has distinct features and diagnostic tests that can help in differentiating them from infectious mononucleosis. A thorough clinical evaluation, including history, physical examination, and appropriate laboratory tests, is essential for making an accurate diagnosis.