Differential Diagnosis

The patient's presentation with fever, erythematous blanching rash, enlarged tender lymph nodes, and specific laboratory findings suggests a complex immunological and hematological condition. The differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis

  • Angioimmunoblastic T-cell Lymphoma (AITL): This diagnosis is strongly suggested by the cervical lymph node biopsy. AITL is known for its association with systemic symptoms such as fever, rash, and lymphadenopathy, as well as its link with CMV and EBV viremia and the development of Hemophagocytic Lymphohistiocytosis (HLH), which are all present in this patient.

• Other Likely Diagnoses

  • Peripheral T-cell Lymphoma (PTCL): While the biopsy suggests AITL, other types of PTCL could present similarly and should be considered, especially if there are atypical features or if the diagnosis of AITL is not definitive.
  • Severe Infectious Mononucleosis: Given the presence of EBV viremia, a severe form of infectious mononucleosis could be considered, especially if the lymphoma diagnosis is not conclusive. However, the presence of a rash and specific lymph node biopsy findings lean more towards a lymphomatous process.
  • Autoimmune Lymphoproliferative Syndrome (ALPS): This condition can present with lymphadenopathy, splenomegaly, and autoimmune cytopenias, along with an increased risk of lymphoma. The presence of HLH and lymphadenopathy might suggest this diagnosis, but the biopsy findings and viremia point more directly to a lymphoma.

• Do Not Miss Diagnoses

  • Hodgkin Lymphoma: Although less likely given the biopsy results suggesting a T-cell lymphoma, Hodgkin lymphoma can present with similar systemic symptoms and lymphadenopathy. Missing this diagnosis could lead to inappropriate treatment.
  • Severe Combined Immunodeficiency (SCID): This condition, characterized by a profound deficiency in T-cell and sometimes B-cell function, can lead to severe infections, including CMV and EBV, and could potentially present with lymphadenopathy and HLH. However, the age of presentation and specific findings would make this less likely.
  • Lymphoma-associated Hemophagocytic Lymphohistiocytosis (HLH) due to other lymphomas: While AITL is a known cause of HLH, other lymphomas can also trigger this condition. It's crucial to identify and treat the underlying lymphoma to manage HLH effectively.

• Rare Diagnoses

  • Natural Killer (NK)/T-cell Lymphoma: This is a rare and aggressive form of lymphoma that can present with systemic symptoms and lymphadenopathy. It is more common in Asia and is associated with EBV.
  • Adult-onset Still’s Disease: This autoimmune condition can mimic lymphoma with its presentation of fever, rash, and lymphadenopathy. However, the biopsy findings and specific viremia in this case make it less likely.
  • Castleman Disease: A rare disorder that can present with lymphadenopathy, systemic symptoms, and can be associated with lymphoma. It's less likely given the specific biopsy results but could be considered in a differential diagnosis for lymphadenopathy and systemic symptoms.