Oral Candidiasis Thrush

Slide 1 · Oral Candidiasis (Thrush)

Host susceptibility • mucosal morphology • clinicopathologic diagnosis

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Distinguish oral colonization from candidal mucosal infection.

Recognize pseudomembranous, erythematous, and hyperplastic patterns.

Connect host risk, clinical morphology, and diagnostic decisions.

Differentiate thrush from non-scrapable lesions and assess possible extension.

Slide 3 · A commensal organism can become a pathogen

Candida albicans is frequently present without symptomatic infection.

The same organism may produce superficial mucosal disease.

Clinical disease reflects interaction between fungus and oral host milieu.

Positive microbiology alone is not synonymous with candidiasis.

Slide 4 · Normal oral carriage is common

C. Albicans as oral flora in approximately 50% of people.

Carriage describes organism presence, not invasive or symptomatic disease.

Interpret a positive swab in the context of visible lesions and symptoms.

Slide 5 · Colonization-to-infection continuum

Commensal carriage

Ecologic or immune disruption

Mucosal overgrowth / infection

The clinical threshold is defined by compatible mucosal disease, not by recovering Candida alone.

Slide 6 · Three determinants of infection

Fungal factor

C. Albicans strain

Virulence varies among strains

Ecologic factor

Oral microbiome composition

Antibiotics change competition

Host factor

Immune status

Deficient protection increases susceptibility

Slide 7 · Why oral bacterial flora matters

A mixed bacterial community normally shares the oral mucosal niche.

Broad-spectrum antibiotics can eliminate or alter bacterial flora.

The altered ecosystem can permit a candidal bloom and thrush.

Slide 8 · Antibiotic-associated thrush: Causal sequence

Broad-spectrum antibiotic

Oral bacterial community altered

Candida expands

Pseudomembranous lesions

The causal sequence explains why fungal disease may follow antibacterial therapy.

Slide 9 · Strain-dependent susceptibility

The C. Albicans strain as a disease determinant.

Organism identity alone does not determine clinical severity.

Host and community factors modify whether infection manifests.

Slide 10 · Immunosuppression removes a key restraint

Immunosuppression as the principal context for deeper risk.

Oral mucosal candidiasis ordinarily remains superficial.

Immune compromise can increase persistence and disease burden.

Slide 11 · Important high-risk clinical settings

Transplantation

Solid-organ transplant

Hematopoietic stem-cell transplant

Hematologic / oncologic

Neutropenia

Chemotherapy-related immunosuppression

Systemic disease

AIDS / advanced HIV

Diabetes mellitus

Slide 12 · Transplant-associated risk

Both organ and hematopoietic stem-cell transplantation are named.

Immune suppression after transplantation creates a susceptible host.

Examine new white mucosal lesions rather than assuming they are nonspecific.

Slide 13 · Neutropenia and candidiasis

Neutropenia is explicitly identified as a predisposing clinical condition.

Reduced innate defenses permit opportunistic fungal infection.

In neutropenic patients, oral lesions require attention to overall clinical context.

Slide 14 · Chemotherapy-associated susceptibility

Chemotherapy can produce immunosuppression and mucosal vulnerability.

A new coating or erythematous lesion should trigger clinical assessment.

Severe host immunosuppression alters the concern for extension beyond the mouth.

Slide 15 · AIDS and oral candidiasis

AIDS among the causes of increased susceptibility.

NIH recognizes oral/esophageal candidiasis as manifestations of immune suppression in HIV.

The lesion warrants attention to immune status and associated symptoms.

Slide 16 · Diabetes as a host factor

Diabetes is explicitly included among Robbins risk conditions.

In a patient with recurrent or atypical thrush, systemic context matters.

Candida presence without disease still requires careful interpretation.

Slide 17 · Local predisposition: Beyond the Robbins core

DermNet notes dentures and inhaled corticosteroids as promoting conditions.

Other local modifiers include smoking and oral dryness.

Risk assessment should combine systemic immunity and local mucosal ecology.

Slide 18 · Systemic and local susceptibility

Systemic susceptibility

Local and ecological susceptibility

HIV-associated immune suppression

Neutropenia or chemotherapy

Organ or stem-cell transplantation

Diabetes mellitus

Recent broad-spectrum antibiotics

Dentures or altered local environment

Inhaled corticosteroids

Dryness and smoking

Slide 19 · From altered defenses to a visible lesion

Host or microbial shift

Candida predominance

Superficial epithelial inflammation

Clinical mucosal change

A white membrane is one possible clinical expression; Erythema or hyperplasia can predominate.

Slide 20 · Three major mucosal forms

Pseudomembranous

Gray-white superficial membrane

Typically removable

Erythematous

Predominantly red mucosal change

Plaque may be absent

Hyperplastic

Persistent white plaque

Non-scrapable pattern

Slide 21 · Thrush means pseudomembranous disease

A superficial gray-to-white inflammatory membrane is characteristic.

Lesions represent fungal organisms admixed with inflammatory exudate.

The membrane is typically easy to scrape from the underlying mucosa.

Slide 22 · The pseudomembrane is a composite

Matted fungal organisms.

They are enmeshed in fibrinosuppurative exudate.

The gray-white coating is inflammatory material—not simply keratin.

Slide 23 · Pseudomembrane architecture: Schematic

Fungi + fibrinopurulent exudate

Erythematous inflamed mucosal surface

Detachable surface layer

Schematic cross-section — not a histologic specimen

Slide 24 · Why removal reveals an erythematous base

The superficial layer can be detached from the inflamed mucosal surface.

After removal, an erythematous inflammatory base is exposed.

This surface response helps distinguish thrush from adherent keratotic plaques.

Slide 25 · Where pseudomembranes may occur

NIH describes lesions on the tongue and buccal mucosa.

The hard palate, soft palate, gums, and oropharynx may also be involved.

Anatomic distribution alone is less discriminating than the characteristic removable coating.

Slide 26 · Removable vs persistent white plaques

Pseudomembranous Candida

Non-removable plaque

Creamy or gray-white surface material

Scrapes off in many cases

Inflamed mucosa may be exposed

Confirm risk factors and symptoms

Persistent white lesion

Consider hyperplastic Candida or other causes

Hairy leukoplakia is an important alternative

Persistent unexplained lesions need evaluation

Slide 27 · Erythematous oral candidiasis

This is a recognized form, even without a white membrane.

Clinical appearance may be dominated by smooth red mucosal areas.

Tenderness or burning may be prominent in symptomatic patients.

Slide 28 · An atrophic red pattern may follow antibiotics

DermNet describes acute atrophic candidiasis with red shiny patches.

A sore tongue after antibiotic use is a meaningful clinical clue.

Do not require a visible white pseudomembrane for every diagnosis.

Slide 29 · Denture-associated mucosal erythema

Chronic atrophic candidiasis can occur under dentures.

The denture-bearing mucosa may be erythematous and inflamed.

Assess the prosthesis, hygiene, and other coexisting local factors.

Slide 30 · Median rhomboid glossitis

DermNet includes a central posterior-tongue erythematous pattern.

It appears as a circumscribed, often diamond-shaped area.

Interpret the finding in clinical context; Not all tongue erythema proves Candida.

Slide 31 · Angular cheilitis: An associated pattern

Inflammation and fissuring affect one or both oral commissures.

Candida can contribute, sometimes with bacterial coinfection.

Local saliva-related irritation can contribute independently.

Slide 32 · Hyperplastic candidiasis

A hyperplastic form of oral candidiasis.

The lesion may produce a chronic, non-scrapable white plaque.

Persistent lesions require evaluation for another keratotic disorder or dysplasia.

Slide 33 · Three forms: Morphology and bedside clue

Form

Dominant appearance

Practical discriminator

Pseudomembranous

White / gray coating

Often wipes away

Erythematous

Red smooth area

May lack white plaque

Hyperplastic

Persistent white plaque

Does not scrape away

Slide 34 · Symptoms can be variable

NIH describes many white oral lesions as painless.

Erythematous disease may cause soreness or a burning sensation.

Symptoms alone cannot establish the subtype or exclude another diagnosis.

Slide 35 · Why immunologic context changes interpretation

Superficial Candida in a healthy host usually has limited anatomic extent.

In marked immunosuppression, infection can be more persistent.

Screen for swallowing symptoms that suggest esophageal involvement.

Slide 36 · Oropharyngeal vs esophageal candidiasis

Oropharyngeal disease causes oral or pharyngeal mucosal lesions.

Esophageal involvement may cause odynophagia and dysphagia.

Esophageal disease can occur even when oral thrush is absent.

Slide 37 · Oropharyngeal and esophageal patterns

Oropharyngeal candidiasis

Esophageal candidiasis

Typical removable surface plaques

Tongue, buccal mucosa, palate

Clinical diagnosis often sufficient

Topical or systemic therapy by severity

Retrosternal pain or burning

Odynophagia / dysphagia

May occur without oral lesions

Requires systemic antifungal therapy

Slide 38 · Oral findings can signal immune dysfunction

In people with HIV, thrush often occurs with significant immune suppression.

NIH reports that oral or esophageal candidiasis is most often seen with CD4 counts below 200 cells/mm³.

A single oral lesion does not independently quantify immune function.

Slide 39 · A lesion-to-laboratory diagnostic sequence

Recognize clinical morphology

Assess host risk and symptoms

Scraping / microscopy if needed

Biopsy for atypical persistent lesions

The decision to test depends on uncertainty, severity, treatment response, and alternate diagnoses.

Slide 40 · Clinical diagnosis is usually the starting point

Typical removable plaques support a clinical diagnosis of thrush.

Look for an erythematous base and compatible susceptibility factors.

Consider alternatives if the lesion is atypical or does not respond as expected.

Slide 41 · Yeast and filamentous forms: Schematic

Conceptual fungal forms examined in an oral scraping

Budding yeast forms

Elongated filamentous forms

Educational schematic: Demonstration of fungal forms must be interpreted with the clinical lesion.

Slide 42 · Direct microscopy and potassium hydroxide

An oral scraping can be examined by potassium hydroxide preparation.

Characteristic budding yeasts and filamentous forms support the diagnosis.

Correlate with visible disease, because colonization can also occur.

Slide 43 · Culture: Useful but not diagnostic in isolation

Culture can identify the Candida species recovered.

Because Candida may colonize normal mucosa, a positive culture is not enough.

Culture or further testing is useful when the presentation or response is atypical.

Slide 44 · Tissue biopsy: When the pattern is discordant

Persistent non-scrapable plaques merit evaluation for other pathology.

Biopsy may be needed when leukoplakia or dysplasia is a concern.

Tissue interpretation must distinguish surface colonization from lesion causation.

Slide 45 · Histologic principle: Organisms plus tissue response

Fungal forms and surface inflammatory change may coexist.

Inflammatory exudate explains the pseudomembranous coating.

Pathology is most persuasive when organisms and lesional inflammation fit the clinical presentation.

Slide 46 · White mucosal lesions: Diagnostic contrast

Feature

Thrush

Oral hairy leukoplakia

Surface

Creamy removable material

Hairy / corrugated keratosis

Scraping

Often removable

Not scrapable

Etiology

Candida-associated

Epstein–Barr virus

Clinical context

Various susceptible hosts

Often immunocompromised

Slide 47 · Oral hairy leukoplakia is not thrush

Hairy leukoplakia to Epstein–Barr virus.

It typically involves the lateral border of the tongue.

The lesion does not scrape off, unlike classic pseudomembranous Candida.

Candida may secondarily coexist, complicating surface appearance.

Slide 48 · Persistent leukoplakia is a different problem

Leukoplakia is a clinical designation for a persistent white plaque requiring exclusion of other causes.

One cannot label all non-scrapable plaques as chronic Candida.

Assess for dysplasia or neoplasia when clinically warranted.

Slide 49 · Candida infection vs herpes infection

Oral candidiasis

Oral herpes simplex

White pseudomembrane or erythema

Many plaques wipe off

Fungal forms may be found

Strongly shaped by host factors

Vesicles and subsequent ulcers

Ulcerative rather than fungal plaques

Often painful primary stomatitis

Viral process; Different workup

Slide 50 · Broad oral differential: Pattern first

Scrapable white coating: Consider pseudomembranous Candida.

Persistent white plaques: Assess hairy leukoplakia and leukoplakia.

Predominantly red lesions: Consider erythematous Candida and other mucosal disorders.

Discrete vesicles or ulcers: Investigate nonfungal etiologies.

Slide 51 · When oral white plaques are found

1. Inspect distribution, texture, and adjacent mucosa

2. Determine whether the surface plaque is removable

3. Review antibiotics, immune suppression, diabetes, and local modifiers

4. If atypical, persistent, or treatment-refractory, obtain further evaluation

5. Ask about swallowing pain, dysphagia, and substernal discomfort

Slide 52 · Mild oropharyngeal disease: Local therapy

IDSA recommends topical approaches for mild disease.

Examples include clotrimazole troches and miconazole buccal tablets.

Nystatin suspension or pastilles are alternative topical options.

Treatment selection depends on patient factors and local availability.

Slide 53 · Moderate-to-severe disease: Systemic therapy

IDSA recommends oral fluconazole for moderate-to-severe oropharyngeal candidiasis.

The guideline distinguishes this from topical management of mild disease.

Drug interactions, tolerability, and underlying conditions require clinical review.

Slide 54 · Esophageal symptoms alter treatment requirements

Esophageal candidiasis requires systemic antifungal therapy.

Oral-only topical regimens are not appropriate for esophageal infection.

Assess dysphagia or odynophagia before assuming disease is restricted to the mouth.

Slide 55 · Refractory disease requires reassessment

Re-evaluate diagnosis, adherence, and immune or local predisposing factors.

Non-albicans species and reduced azole susceptibility may contribute.

IDSA provides alternative systemic agents for fluconazole-refractory disease.

Slide 56 · Why candidiasis recurs

Persistent immune / local risk

Repeated fungal overgrowth

Recurrent mucosal disease

Re-evaluate predisposing factor

Symptom treatment without addressing major susceptibility factors can be followed by recurrence.

Slide 57 · Local risk modification

Review denture hygiene and fit when a prosthesis is involved.

Assess inhaled corticosteroid technique and local oral care.

Use antibacterial agents appropriately; Unnecessary spectrum may perturb flora.

Evaluate relevant systemic conditions when infection is recurrent.

Slide 58 · Deep fungal infections: Adjacent Robbins scope

Robbins groups several deeper fungal infections under head-and-neck disease.

Named agents include Histoplasma, Blastomyces, Coccidioides, Cryptococcus, mucormycosis, and aspergillosis.

These infections are distinct from routine superficial oral thrush.

Slide 59 · When the oral fungal differential broadens

Marked immunocompromise increases concern for unusual fungal disease.

Atypical ulcerating or destructive lesions should not be assumed to be Candida.

Escalate diagnostic investigation when morphology or course is discordant.

Slide 60 · Case 1: White coating after antibiotics

A patient develops removable creamy plaques on the tongue shortly after a course of broad-spectrum antibiotics. Red mucosa is visible after gentle removal.

Discuss

Identify the most likely candidal form.

Explain why antibiotics could be a trigger.

Explain why a positive swab alone is insufficient.

Slide 61 · Case 2: Transplantation and painful swallowing

A transplant recipient has oral plaques and new odynophagia, together with a markedly immunosuppressed clinical state.

Discuss

Which symptom raises concern for esophageal disease?

Why is management different from mild, isolated oral thrush?

Which host factor is central to the presentation?

Slide 62 · Case 3: A white plaque that cannot be removed

An immunocompromised patient has a persistent corrugated white plaque along the lateral tongue; Gentle scraping does not remove it.

Discuss

What competing diagnosis deserves attention?

Which bedside feature opposes classic thrush?

Why is the label “Candida” premature?

Slide 63 · Clinicopathologic synthesis

Candida can be commensal: Distinguish carriage from disease.

The pseudomembrane contains fungi and inflammatory exudate.

Scrapability, mucosal response, and host risk guide recognition.

Systemic symptoms and atypical persistence demand further evaluation.

Slide 64 · Selected references

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th ed. 2026. Chapter 16: Head and Neck, pp. 666–667.

NIH/CDC/HIVMA. HIV Opportunistic Infections Guidelines: Mucocutaneous Candidiasis. Updated 2024; reviewed 2026.

Pappas PG, et al. IDSA Clinical Practice Guideline for the Management of Candidiasis. 2016 update.

DermNet. Oral candidiasis; Candidiasis pathology; Angular cheilitis.