Which infections of the oropharynx can present with fever and leukopenia?

Oropharyngeal Infections Causing Fever and Leukopenia

Epstein-Barr virus (infectious mononucleosis) is the most important viral oropharyngeal infection that classically presents with fever and leukopenia, while human herpesvirus-6 is an emerging recognized cause of this presentation.

Primary Viral Causes

Epstein-Barr Virus (Infectious Mononucleosis)

• EBV is explicitly identified as a frequent cause of acute pharyngitis that presents with generalized lymphadenopathy and splenomegaly 1
• Leukopenia can occur in the early phase of infectious mononucleosis, though atypical lymphocytosis is more characteristic later in the disease course
• Look for: posterior cervical lymphadenopathy, splenomegaly, tonsillar exudates, and palatal petechiae

Human Herpesvirus-6 (HHV-6)

• A documented case demonstrates HHV-6 causing fever, leukopenia (WBC as low as 1.8 k/mcL), oral mucous membrane plaques, and lymphadenopathy 2
• This patient also developed a progressive morbilliform rash and elevated liver enzymes
• HHV-6 should be considered when viral cultures for more common agents are negative

Other Viral Agents

Additional viruses causing oropharyngeal infection with potential for leukopenia include 1:

• Cytomegalovirus (CMV) - can cause systemic infection with pharyngitis
• HIV (acute retroviral syndrome) - presents with pharyngitis, fever, and often leukopenia
• Adenovirus, influenza, and other respiratory viruses (though these typically cause leukocytosis rather than leukopenia)

Bacterial Considerations

Group A Streptococcus

• GAS is the most common bacterial cause of pharyngitis but typically causes leukocytosis, NOT leukopenia 1
• The presence of leukopenia should prompt consideration of viral rather than typical bacterial causes

Immunocompromised Patients

In patients with hematologic malignancies or neutropenia, a different pattern emerges:

• Candidiasis and infected mucosal ulcers are the most prevalent oral infections in immunocompromised patients with fever 3
• Gram-negative bacilli (Klebsiella, Enterobacter, Proteus, Pseudomonas) colonizing the oropharynx significantly increase infection risk 4
• These patients have leukopenia as their underlying condition, not as a result of the infection

Clinical Pitfalls

Critical distinction: Most common bacterial pharyngitis (GAS) causes fever WITH leukocytosis. The combination of fever AND leukopenia in oropharyngeal infection strongly suggests:

1. Viral etiology (EBV, HHV-6, CMV, acute HIV)
2. Underlying immunosuppression with secondary infection
3. Drug reaction with eosinophilia and systemic symptoms (DRESS syndrome) - as illustrated by the HHV-6 case where antibiotics preceded the presentation 2

Do not assume streptococcal pharyngitis when leukopenia is present - this combination warrants viral testing, consideration of infectious mononucleosis, and evaluation for immunosuppression or drug reactions.