Differential Diagnosis for a 23-year-old Male with Fatigue
Single Most Likely Diagnosis
- Infectious Mononucleosis (Mono): The patient's positive mono screen, high EBV viral capsid Ag (VCA) Ab (IgM), and clinical presentation of fatigue for 2 years support this diagnosis. The presence of IgM antibodies against EBV VCA indicates a recent or current infection.
Other Likely Diagnoses
- Chronic Fatigue Syndrome: Given the patient's prolonged fatigue, this diagnosis should be considered, especially if the infectious mononucleosis has transitioned into a post-infectious fatigue state.
- Viral Reactivation or Chronic EBV Infection: The high IgG levels against EBV VCA and the presence of IgM antibodies suggest either a reactivation of EBV or a chronic infection, which could explain the prolonged fatigue.
Do Not Miss Diagnoses
- Hodgkin Lymphoma: Although less common, EBV is associated with Hodgkin lymphoma. The patient's high white blood cell count and fatigue could be indicative of a lymphoproliferative disorder, making this a critical diagnosis not to miss.
- Immunodeficiency: The inability to clear EBV infection could suggest an underlying immunodeficiency. This would be critical to diagnose to prevent further complications from infections.
Rare Diagnoses
- EBV-associated Hemophagocytic Lymphohistiocytosis (HLH): A rare but potentially life-threatening condition where the immune system produces too many activated immune cells called macrophages and lymphocytes. EBV can trigger HLH, and the patient's prolonged fatigue and abnormal blood counts could be indicative of this condition.
- X-linked Lymphoproliferative Disease (XLP): A rare genetic disorder that affects the immune system's ability to respond to EBV infection, leading to severe illness. The patient's prolonged fatigue and abnormal EBV serology could suggest this diagnosis, although it is rare and typically presents in childhood.