[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Head and neck](https://durgical.com/en/general-pathology/areas/head-neck/) › Oral infections and the mouth in systemic disease

# Oral infections and the mouth in systemic disease

- Lesion

The mouth shows infections (herpes, Candida, fungi) and often gives the first sign of a systemic disease such as HIV, measles or leukaemia.

Updated Nov 12, 2026

## Key points

- Primary herpetic gingivostomatitis in children (HSV-1); recurrent herpes labialis from latent virus in the trigeminal ganglion.
- Herpes cytology: multinucleated giant cells with molded nuclei and intranuclear inclusions (Tzanck smear).
- Candida: pseudomembranous (thrush, scrapes off to a red base), erythematous, hyperplastic; risk with antibiotics, steroids, diabetes, HIV, dentures.
- Deep fungi: histoplasmosis, paracoccidioidomycosis (mulberry-like ulcers, common in rural Latin America), mucormycosis.
- Hairy leukoplakia: white, corrugated plaques on the lateral tongue that do not scrape off; EBV in koilocyte-like cells; not premalignant.
- Systemic signs: Koplik spots (measles), strawberry tongue (scarlet fever), gingival hypertrophy (drugs, monocytic leukaemia), pigmentation (Addison disease, Peutz–Jeghers).

## What it is

Herpes simplex and Candida are the commonest oral infections; deep fungi reach the mouth in endemic areas or in immunosuppression. Many systemic diseases show oral signs early, so the mouth is part of the general exam. Hairy leukoplakia, an EBV lesion on the lateral tongue, points to immunosuppression, classically HIV.

## Structure

- Herpes: intraepithelial vesicles from acantholysis and ballooning; eosinophilic intranuclear inclusions; multinucleated cells.
- Thrush: grey-white membrane of fungal hyphae and yeasts in fibrinosuppurative exudate; PAS or silver stains.
- Hairy leukoplakia: hyperparakeratosis with hair-like projections, ballooned cells with nuclear clearing; EBV by in situ hybridisation; often superficial Candida.
- Paracoccidioidomycosis: pseudoepitheliomatous hyperplasia with granulomas and large multibudding yeasts.

## Step by step

- HSV infects epithelium at the primary site and travels up sensory nerves to establish latency in ganglia.
- Triggers (UV light, fever, stress, immunosuppression) reactivate the virus and it returns to the lip or mouth.
- Candida, a commensal in about half of people, overgrows when flora, saliva or immunity are disturbed.
- In hairy leukoplakia, EBV replicates in the upper layers of tongue epithelium when T-cell control is weak.
- Systemic diseases alter blood cells, immunity, hormones or nutrition and show first in the fast-renewing oral mucosa.

## White patches in the mouth

| Lesion | Scrapes off? | Cause | Premalignant? |
| --- | --- | --- | --- |
| [Thrush (pseudomembranous candidiasis)](https://durgical.com/en/conditions/candidiasis-oral-oesophageal-and-invasive/) | Yes, leaves a red base | Candida albicans | No |
| [Hairy leukoplakia](https://durgical.com/en/conditions/hiv-infection-and-aids/) | No | EBV in immunosuppression | No |
| [Leukoplakia](https://durgical.com/en/conditions/head-and-neck-squamous-cell-carcinoma/) | No | Often tobacco; unknown | Yes, must be biopsied |
| Lichen planus | No | T-cell immune reaction | Small risk in erosive forms |

## Clinical notes

- Thrush in an adult without obvious cause suggests HIV, diabetes or inhaled steroid use.
- Hairy leukoplakia in a person with HIV may herald progression to AIDS.
- Painful mulberry-like ulcers and lung disease in a rural worker suggest paracoccidioidomycosis.

## Memory aid

Thrush wipes off; hairy and leuko stay on: only leukoplakia earns a biopsy for cancer.

## Test yourself

Think of the answer, then tap the question to see it.

## How is thrush distinguished from leukoplakia at the bedside?

Thrush is a membrane that scrapes off leaving a red, raw base; leukoplakia cannot be scraped off.

## What causes oral hairy leukoplakia and where does it occur?

Epstein–Barr virus replicating in the epithelium, in immunosuppressed people; on the lateral border of the tongue.

## Where does HSV-1 remain latent after primary oral infection?

In the sensory neurons of the trigeminal ganglion.

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## Connections

## Related 4

- [Aphthous ulcers and reactive oral lesions](https://durgical.com/en/general-pathology/aphthous-ulcers-and-reactive-oral-lesions/)
- [Leukoplakia and erythroplakia](https://durgical.com/en/general-pathology/leukoplakia-and-erythroplakia/)
- [Chemical and infectious oesophagitis](https://durgical.com/en/general-pathology/chemical-and-infectious-oesophagitis/)
- [The lung in immunocompromise and transplant](https://durgical.com/en/general-pathology/the-lung-in-immunocompromise-and-transplant/)

## Related conditions 6

- [Genital herpes (herpes simplex infection)](https://durgical.com/en/conditions/genital-herpes/)
- [Candidiasis: oral, oesophageal and invasive](https://durgical.com/en/conditions/candidiasis-oral-oesophageal-and-invasive/)
- [Paracoccidioidomycosis](https://durgical.com/en/conditions/paracoccidioidomycosis/)
- [Histoplasmosis](https://durgical.com/en/conditions/histoplasmosis/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Measles](https://durgical.com/en/conditions/measles/)

## Microorganisms 4

- [Herpes simplex virus 1](https://durgical.com/en/microbiology/herpes-simplex-virus-1/)
- [Candida albicans](https://durgical.com/en/microbiology/candida-albicans/)
- [Epstein–Barr virus](https://durgical.com/en/microbiology/epstein-barr-virus/)
- [Paracoccidioides brasiliensis](https://durgical.com/en/microbiology/paracoccidioides-brasiliensis/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Mouth Disorders](https://medlineplus.gov/mouthdisorders.html) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/oral-infections-and-the-mouth-in-systemic-disease/