Dermatology MCQ - Viral Infections - Cytomegalovirus infection

55-year-old man, 3 months post-kidney transplant on immunosuppressive therapy (tacrolimus, mycophenolate mofetil, prednisone), presents with fever, fatigue, and pancytopenia. Endoscopy reveals ulcerations in the stomach and colon. Biopsies of the gastrointestinal mucosa show large cells with intranuclear inclusions surrounded by a clear halo, and cytoplasmic inclusions. Which of the following is the most likely causative agent and the best diagnostic test to confirm this infection?

A) Epstein-Barr virus; EBV viral load by PCR
B) Cytomegalovirus; CMV pp65 antigenemia assay or PCR
C) Adenovirus; viral culture from stool
D) Herpes simplex virus; Tzanck smear
E)Clostridium difficile; stool toxin assay

Correct Answer: B) Cytomegalovirus; CMV pp65 antigenemia assay or PCR

Explanation

This presentation is classic for cytomegalovirus (CMV) infection in an immunocompromised host, particularly a solid organ transplant recipient.

Key Features of CMV Infection in Immunocompromised Patients:

• Clinical Presentation:

  • Fever, fatigue, and bone marrow suppression (pancytopenia).

  • Gastrointestinal involvement: Esophagitis, gastritis, or colitis with ulcerations (can cause abdominal pain, diarrhea, or bleeding).

• Histopathology:

  • "Owl's eye" inclusions: Large intranuclear inclusions surrounded by a clear halo (due to viral aggregates).

  • Cytoplasmic inclusions may also be present.

• Risk Factors: Immunosuppression (especially with T-cell inhibitors like tacrolimus), primary infection, or reactivation of latent CMV.

Diagnostic Approach:

• Best Diagnostic Test:

  • CMV PCR (quantitative viral load in blood) or pp65 antigenemia assay (detects CMV phosphoprotein 65 in leukocytes). These tests are highly sensitive and specific for active CMV viremia.

  • Histopathology of tissue biopsies (as described) is characteristic but invasive.

• Why Not Other Tests?

  • Culture is slow and less sensitive.

  • Serology (IgG/IgM) is not useful for diagnosing active infection in immunocompromised hosts.

Why Not the Other Options?

• (A) Epstein-Barr virus: Causes mononucleosis or post-transplant lymphoproliferative disorder (PTLD), not typically GI ulcers with "owl's eye" inclusions.

• (C) Adenovirus: Can cause gastroenteritis or hemorrhagic colitis but has smudge cells on histology, not "owl's eye" inclusions.

• (D) Herpes simplex virus: Causes vesicular lesions or ulcers but is limited to squamous epithelium (oral/genital), not deep GI ulcers. Tzanck smear shows multinucleated giant cells, not inclusions.

• (E) Clostridium difficile: Causes pseudomembranous colitis with neutrophil infiltrates, not viral inclusions.

Management:

• First-line treatment: Intravenous ganciclovir or oral valganciclovir.

• Reduce immunosuppression if possible.

• Prophylaxis: High-risk patients (CMV-seronegative recipient with seropositive donor) often receive antiviral prophylaxis post-transplant.

Prognosis:
Treatable with antivirals, but delayed diagnosis can lead to disseminated disease (retinitis, pneumonitis) or graft loss.

Note: CMV is a common opportunistic infection post-transplant, and vigilance is required for early detection.