Fungal infections

Chapter 9

Fungal infections

A variety of diseases caused by fungi may appear in the oral and perioral regions, either as localized lesions or as manifestations of systemic mycoses. However, candida infections of the oral cavity are by far the predominant group of fungal infections which the dental practitioners in the Western world frequently encounter, although rare mycoses such as blastomycosis and mucormycosis may be seen, particularly in immunocompromised and sometimes in immigrant population groups. Hence, the emphasis of this chapter is on candida infections of the oral mucosa; the uncommon mycoses are briefly discussed at the end of the chapter (and see Table 9.5).

Table 9.5

Uncommon systemic mycoses and their oral manifestations

Disease and representative agent Main sites affected Major oral manifestations Frequency of oral affection
Aspergillosis Aspergillus fumigatus Paranasal sinuses; rarely tongue, soft palate Plaque formation and intense local pain in oral lesions Uncommon
Blastomycosis (North American)Blastomyces dermatitidis Tongue, oral mucosa, gingivae, lip, mandibular bone Ulceration, sessile projections, indurated swellings, actinomycosis like draining abcesses Rare
Coccidioidomycosis Coccidioides immitis Nasolabial folds, skin Verrucous granulomas’ resembling carcinomas Very rare
CryptococcosisaCryptococcus neoformans Gingiva, hard and soft palate, mucosa, tonsillar pillar Violaceous coloured nodules orgranulations, swellings, ulcers Uncommon
Geotrichosis Geotrichum candidum Oral mucosa Similar to acute pseudomembranes of candidosis Uncommon
HistoplasmosisbHistoplama capsulatum Histoplasma duboisii Oral mucosa, tongue, palate, gingiva, periapical area Nodular, indurated or granular masses or tissue destruction with bone erosion 40%
Mucormycosis Mucor species Extension from maxillary sinus through palate into the mouth Sloughing ulcers with grey eschar and exposed bone (especillary maxilla); unilateral facial pain. Common
Paracoccidioidomycosis(South American blastomycosis)Paracoccidioides brasiliensis Hard and soft palate, gingiva, tongue Papules or vesicles leading to ulcers; extensive local destruction Common
Sporotrichosis Sporotrichum schenckii Oral mucosa Erythematous, ulcerative lesions leading to granuloma, or papillomas Uncommon

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aAIDS associated oral lesions have been described.

bMay present to the dentist with initial oral manifestations.

A number of local and general predisposing factors play a contributory role in the pathogenesis of oral fungal infections. Debilitated individuals, eg. those receiving antibiotics, steroid or cytotoxic therapy, are particularly predisposed, as are patients with uncontrolled diabetes mellitus, other hormonal disorders such as hypoadrenocorticism, and haematogenous and malignant disorders. Certain age groups, especially the very young and the very old, and the pregnant are prone to oral yeast infections.

The effects of local factors are particularly well seen in chronic atrophic candidosis. Unclean dentures which may act as the reservoir of yeasts may be an aetiological cofactor, as is mechanical trauma due to an ill-fitting denture. Local use of antibiotics and corticosteroids may predispose to oral candidosis, together with other factors which are listed in Table 9.1.

Table 9.1

Factors that predispose the host to oral candidosis

Physiological: Old age, infancy, pregnancy
Local trauma: Mucosal irritation, denture wearing
Antibiotics: Particularly broad-spectrum antibiotics
Corticosteroids: Steroid inhalers, systemic steroids
Malnutrition: High carbohydrate diet; deficiencies in iron, folate, vitamin B12
Endocrine disorders: Hypoendocrine states (e.g. hypothyroidism, Addison’s disease), diabetes mellitus
Malignancies: Blood disorders (e.g. acute leukaemia, agranulocytosis)
Immune defects: AIDS, thymic aplasia
Xerostomia: Due to irradiation, drug therapy, Sjögren’s syndrome (primary and secondary), cytotoxic drug therapy

Oral candidosis

Oral candidosis is a clinical entity which has been known since antiquity and manifests in a variety of ways. Accordingly, the disease has been categorized into several descriptive categories as localized candidoses which are confined to the oral and perioral tissues, and rare systemic disorders where candidosis may affect other organ systems as well as the oral cavity.

The variety of clinical types of candidosis is matched by a variety of causative yeast species. The imperfect fungus Candida albicans is the best known and the commonest but at least twelve other Candida species have been isolated from the oral cavity. They include Candida glabrata, Candida tropicalis, Candida pseudotropicalis, Candida guilliermondii and Candida krusei. In addition to Candida species other yeasts (Rhodotorula spp., Saccharomyces spp.) may also be present but make up only a small proportion of total yeast isolates.

Candida albicans is a dimorphic fungus and basically exists in the classical ovoid, yeast or blastospore phase (syn. blastoconidia) and hyphal or mycelial phases (Figure 9.1). They multiply primarily by the production of buds from ovoid yeast cells. Under adverse conditions they also form spores called chlamydospores which are not usually observed in clinical specimens but can assist in the laboratory identification of yeasts.

Oral carriage of Candida species in adults range from 20–60% and, on average, about 40% of humans harbour the yeast as an innocuous commensal. The yeast is also present in the throat, large bowel and vagina. The primary oral reservoir of the organism in carriers is the dorsum of the tongue.

Candidoses confined to the oral and perioral tissues

Candidoses which are relatively common but confined to the oral and perioral tissue can be classified as shown in Table 9.2.

Table 9.2

Classification of oral candidosis. Group I: Common disorders confined to the oral and perioral tissues

Subgroup Acute/chronic Disease state Synonym(s)
1 Acute Acute pseudomembranous Thrush
2 Acute Acute atrophic Candida glossitis/glossodynia
3 Chronic Chronic hyperplastic candidosis Candida leukoplakia
4 Chronic Chronic atrophic candidosis: Denture sore mouth, denture-induced stomatitis
    Newton‘s Type I: pin-point lesions Localized simple inflammation
    Newton‘s Type II: diffuse erythema Generalized simple inflammation
    Newton‘s Type III: granular Papillary hyperplasia
5 Acute/chronic Angular cheilitis Perlèche

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Acute pseudomembranous candidosis (thrush)

Thrush, or acute pseudomembranous candidosis, is a well-known disease entity associated with a local disturbance or systemic illness. Thrush occurs in up to 5% of newborn infants and in some 10% of elderly, debilitated individuals. In the former it is the immature host defences which mediate the disease while in the latter it could be due to one or more of the predisposing factors mentioned in Table 9.1.

Thrush has recently acquired a renewed importance as it is one of the earliest and sometimes the initial manifestation of acquired immunodeficiency syndrome (AIDS). However, in association with AIDS this lesion may persist for months and the term ’acute’ seems to be inaccurate in this context (see also Chapter 15).

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Mar 12, 2016 | Posted by in General Dentistry | Comments Off on Fungal infections
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