Oral candidiasis is often known as
thrush because its white spots resemble the breast of the bird with the same name. Although candida is present in 50% of healthy mouths, it causes infection (candidiasis) when increased numbers of yeast cells invade the mucosa (the name for the moist skin inside body openings).
Predisposing factors for infection
- Infancy or old age
- Serious underlying disease, such as cancer, primary immunodeficiency or infection with human immunodeficiency virus
- Dry mouth due to disease of the salivary glands or medications e.g. antihistamines, diuretics
- Dentures (especially if they are not regularly cleaned or fit badly)
- Injury to the mouth
- Nutritional deficiency e.g. iron &/or B-vitamin deficiency
- Inhaled corticosteroids used to treat asthma e.g. beclometasone, budesonide, fluticasone. Drink water after inhalation to reduce this complication
The usual organism is Candida albicans, but C. tropicalis is sometimes responsible.
Thrush in a baby
Candida may arise suddenly as an acute infection or persist for long periods as a chronic infection.
- Acute pseudomembranous candidiasis. There are white patches on gums, tongue and inside the mouth that can be peeled off leaving a raw area.
- Acute atrophic candidiasis. There are smooth red shiny patches on the tongue. The mouth is very sore.
- Chronic atrophic candidiasis. This is common in those with dentures. The underlying mucosa is red and swollen.
- Angular cheilitis. There are sore red splits at each side of the mouth, more likely if there is overhang of the upper lip over the lower lip causing a moist deep furrow. Angular cheilitis due to candida and/or Staphylococcus aureus arises frequently in those taking the medication isotretinoin for acne; this medication dries the lips.
- Chronic hyperplastic candidiasis. This is a type of oral leukoplakia (white patch) inside the cheeks or on the tongue with persistent nodules or lumps. It usually affects smokers and is pre-malignant. Red patches (erythroplakia) as well as white patches may indicate malignant change.
- Chronic mucocutaneous candidiasis presents as a chronic pseudomembranous infection. The skin and nails are also affected.
- Median rhomboid glossitis - there is diamond-shaped inflammation at the back of the tongue.
- Candida can cause secondary infection of other skin conditions such as lichen planus or geographic tongue.
Severe infections may extend down the throat (oesophageal infection).
How is the diagnosis of oral candidiasis made?
Microscopy and culture of skin swabs and scrapings aid in the diagnosis of candidal infections. However, candida can live on a mucosal surface quite harmlessly. It may also secondarily infect an underlying disorder.