Introduction

Epstein-Barr virus (EBV; Human herpesvirus 4) is an oncogenic herpesvirus with marked importance in immunosuppressed patients, especially those with Human immunodeficiency virus infection (HIV/AIDS).

In AIDS, impaired T-cell immune surveillance permits:

• EBV reactivation

• Uncontrolled B-cell proliferation

• EBV-driven epithelial lesions

• Lymphoproliferative disorders

The two most important dermatologic/oral board-level associations are:

1. Oral hairy leukoplakia (OHL)

2. EBV-associated lymphoproliferative disorders (LPDs)

FOUNDATIONS (First Principles)

Normal EBV Biology

EBV infects:

• B lymphocytes

• Oropharyngeal epithelial cells

Primary infection occurs via saliva.

After infection:

• Virus establishes lifelong latency in B cells.

Normal Immune Control

CD8+ cytotoxic T cells normally suppress:

• EBV-infected B cells

• Viral replication

This immune surveillance prevents:

• Excessive B-cell proliferation

• Oncogenesis

Why AIDS Predisposes to EBV Disease

In AIDS:

• CD4 depletion impairs cellular immunity.

• Cytotoxic T-cell surveillance becomes ineffective.

Consequences:

• EBV reactivation

• Persistent epithelial infection

• Uncontrolled B-cell proliferation

• Lymphomagenesis

EBV VIROLOGY IMPORTANT FOR EXAMS

EBV expresses latent proteins:

• EBNA (Epstein-Barr nuclear antigens)

• LMP (latent membrane proteins)

These promote:

• B-cell survival

• Proliferation

• Immortalization

ORAL HAIRY LEUKOPLAKIA (OHL)

Definition

Oral hairy leukoplakia is an EBV-induced hyperplastic epithelial lesion occurring predominantly in immunosuppressed patients, especially HIV/AIDS.

It is:

• NOT premalignant

• Strongly associated with immunosuppression

EPIDEMIOLOGY

Occurs mainly in:

• Advanced HIV infection

• Low CD4 counts

Also seen in:

• Organ transplant recipients

• Other immunosuppressed states

CLINICAL FEATURES

Morphology

• White corrugated plaques

• Vertical folds/ridges

• “Hairy” appearance

Common Site

Classic location:

• Lateral border of tongue

May also involve:

• Ventral tongue

• Buccal mucosa rarely

Clinical Characteristics

• Usually asymptomatic

• Non-removable white plaque

Important distinction:
Unlike candidiasis, it cannot be scraped off.

FOUNDATIONS (Histologic First Principles)

Normal Oral Epithelium

Oral mucosa normally consists of:

• Stratified squamous epithelium

• Ordered maturation

• Minimal keratinization on lateral tongue

EBV infects epithelial cells and alters maturation.

INITIATING EVENT

EBV reactivation within oral epithelial cells due to immunosuppression.

Reduced immune control permits:

• Productive viral replication

• Epithelial hyperplasia

PATHOGENESIS

Step 1: HIV-Induced Immunosuppression

CD4 decline weakens EBV control.

Step 2: EBV Replication in Epithelium

Virus infects squamous epithelial cells.

Step 3: Altered Keratinocyte Differentiation

Viral proteins disturb:

• Maturation

• Keratin production

Step 4: Hyperkeratosis and Acanthosis

Produces:

• White plaque

• Corrugated surface

HISTOPATHOLOGY

1. FOUNDATIONS

Normal oral epithelium demonstrates:

• Stratified maturation

• Uniform nuclei

• Minimal surface keratinization laterally

2. HISTOLOGIC FEATURES

Hyperparakeratosis

Thickened keratin layer retaining nuclei.

Why?
Accelerated abnormal epithelial maturation due to EBV infection.

Produces:

• White clinical appearance

Acanthosis

Thickened spinous layer.

Due to:

• Epithelial hyperplasia

Surface Corrugation

Produces “hairy” clinical morphology.

Balloon Cells

Upper epithelial cells appear:

• Enlarged

• Pale

Reflects:

• Viral cytopathic effect

Nuclear Beading / Peripheral Chromatin

Characteristic EBV cytopathic change.

Nuclei show:

• Peripheral chromatin condensation

Minimal Inflammation

Unlike candidiasis or lichen planus.

Reason:
This is mainly viral epithelial hyperplasia rather than destructive inflammation.

3. TEMPORAL EVOLUTION

Early

Subtle epithelial thickening.

Established

Prominent:

• Hyperparakeratosis

• Corrugation

• Viral cytopathic changes

4. NAMING LOGIC

“Hairy”

Refers to:

• Corrugated vertical projections

“Leukoplakia”

Means:

• White plaque

However, unlike true leukoplakia:

• OHL is EBV-driven and not premalignant.

5. STAINING & MARKERS

H&E

Shows:

• Hyperparakeratosis

• Ballooning

• Nuclear changes

EBV In Situ Hybridization (EBER)

Most important diagnostic test.

Detects:

• EBV-encoded RNA

Highly sensitive.

Immunohistochemistry

Less commonly required.

6. PATTERN RECOGNITION & DIFFERENTIAL DIAGNOSIS

Differentiate From Oral Candidiasis

OHL

• Cannot be scraped off

• Corrugated lateral tongue plaque

Oral Candidiasis

Oral candidiasis:

• White plaques removable by scraping

• Pseudomembranes

Differentiate From True Leukoplakia

OHL

• EBV-positive

• Corrugated

• Immunosuppression-associated

Leukoplakia

Oral leukoplakia:

• Dysplasia possible

• Tobacco-related

Differentiate From Lichen Planus

Oral lichen planus:

• Reticular white pattern

• Interface mucositis

7. CLINICO-PATHOLOGICAL CORRELATION

Why Lesions Are White

Hyperkeratosis reflects light and obscures vascular coloration.

Why Lateral Tongue Is Common

High exposure to:

• Mechanical stress

• Viral shedding environment

Why Lesions Are Corrugated

Uneven epithelial hyperplasia and hyperkeratosis produce folds.

MANAGEMENT

Main treatment:

• Antiretroviral therapy (ART)

Lesions may regress with immune restoration.

Antivirals occasionally used:

• Acyclovir

• Valacyclovir

Recurrence common if immunosuppression persists.

EBV-ASSOCIATED LYMPHOPROLIFERATIVE DISORDERS IN AIDS

Overview

EBV drives abnormal proliferation of B cells in immunosuppressed patients.

Spectrum ranges from:

• Reactive proliferation
  to

• Aggressive lymphoma

IMPORTANT AIDS-RELATED EBV-ASSOCIATED DISORDERS

1. Diffuse Large B-cell Lymphoma (DLBCL)

Diffuse large B-cell lymphoma commonly associated with EBV in AIDS.

2. Primary CNS Lymphoma

Primary central nervous system lymphoma strongly associated with EBV.

Important board point:

• EBV positivity in AIDS-related CNS lymphoma is very high.

3. Plasmablastic Lymphoma

Plasmablastic lymphoma:

• Frequently oral

• Strong HIV association

• Often EBV-positive

4. Hodgkin Lymphoma

Hodgkin lymphoma risk is increased in HIV.

Mixed cellularity subtype common.

PATHOGENESIS OF EBV-ASSOCIATED LPDs

Step 1: Immunosuppression

Loss of T-cell surveillance.

Step 2: EBV Latency in B Cells

Virus persists in B lymphocytes.

Step 3: Viral Oncogene Expression

LMP1 acts similarly to constitutive CD40 signaling.

Promotes:

• NF-κB activation

• B-cell survival

• Proliferation

Step 4: Clonal Expansion

Accumulation of mutations → lymphoma.

HISTOPATHOLOGY OF EBV-ASSOCIATED LPDs

Depends on lymphoma type.

GENERAL FEATURES

Large Atypical Lymphoid Cells

Reflect uncontrolled B-cell proliferation.

High Mitotic Activity

Due to aggressive growth.

Necrosis

Common in high-grade lesions.

EBER Positivity

Key diagnostic marker.

PLASMABLASTIC LYMPHOMA HISTOLOGY

Findings

• Large plasmablastic cells

• Immunoblastic morphology

• High Ki-67 index

Often:

• CD138 positive

• CD20 weak/negative

PRIMARY CNS LYMPHOMA

Histology

• Angiocentric lymphoma cells

• Necrosis common

STAINING & MARKERS

EBER In Situ Hybridization

Most important EBV marker.

CD20

B-cell marker.

May be absent in plasmablastic lymphoma.

CD138

Plasma cell differentiation marker.

Ki-67

High proliferation index.

CLINICO-PATHOLOGICAL CORRELATION

Why AIDS Patients Develop EBV Lymphomas

Impaired T-cell control permits persistent proliferative signaling.

Why Oral Cavity Is Commonly Involved in Plasmablastic Lymphoma

Oral mucosa is a major site of EBV persistence and immune dysfunction.

DIFFERENTIAL DIAGNOSIS

Oral Hairy Leukoplakia

• Candidiasis

• Leukoplakia

• Lichen planus

EBV Lymphomas

• Reactive lymphoid hyperplasia

• Other NHL subtypes

• HHV8-associated lymphomas

MANAGEMENT

ORAL HAIRY LEUKOPLAKIA

• ART

• Oral antivirals occasionally

• Usually benign

EBV-ASSOCIATED LYMPHOMAS

• ART optimization

• Chemotherapy

• Rituximab in CD20+ disease

• Radiation in selected CNS disease

PROGNOSIS

OHL

Benign marker of immunosuppression.

EBV-Associated Lymphomas

Often aggressive.

Prognosis depends on:

• CD4 count

• HIV control

• Lymphoma subtype

EXAM-FOCUSED INSIGHTS

• Oral hairy leukoplakia is strongly associated with EBV and HIV/AIDS.

• Classic site = lateral tongue.

• OHL cannot be scraped off.

• OHL is NOT premalignant.

• Hyperparakeratosis and balloon cells are classic histologic findings.

• EBER in situ hybridization is the key diagnostic test.

• AIDS-associated primary CNS lymphoma is strongly EBV-associated.

• Plasmablastic lymphoma commonly involves oral cavity in HIV patients.

• LMP1 acts as an oncogenic signaling protein.

• ART can lead to regression of OHL.

MUST-KNOW BOARD EXAM QUESTIONS

1. Which virus causes oral hairy leukoplakia?

Epstein–Barr virus (EBV).

2. What is the classic site of oral hairy leukoplakia?

Lateral border of the tongue.

3. Can oral hairy leukoplakia be scraped off?

No.

4. Is oral hairy leukoplakia premalignant?

No.

5. What is the most important diagnostic test for EBV in tissue?

EBER in situ hybridization.

6. What histologic feature produces the white appearance of OHL?

Hyperparakeratosis.

7. Which lymphoma is strongly associated with AIDS and EBV in the CNS?

Primary CNS lymphoma.

8. Which aggressive oral lymphoma is classically associated with HIV and EBV?

Plasmablastic lymphoma.

9. What viral protein acts similarly to constitutive CD40 signaling?

LMP1.

10. Why do EBV-associated lymphomas occur in AIDS?

Loss of T-cell immune surveillance permits uncontrolled EBV-driven B-cell proliferation.

11. Which oral condition is an important differential diagnosis for OHL because it can be scraped off?

Oral candidiasis.

12. What is the significance of balloon cells in OHL?

They represent viral cytopathic effect.

13. Which immune cells normally control EBV infection?

CD8+ cytotoxic T cells.

14. Which marker is typically high in plasmablastic lymphoma?

Ki-67 proliferation index.

15. What is the most important treatment for oral hairy leukoplakia in HIV patients?

Effective antiretroviral therapy (ART).