Black hairy tongue  syndrome (BHT) is a condition of the tongue in which the small bumps on the tongue elongate with black or brown discoloration, giving a black and hairy appearance. The appearance may be alarming, but it is a harmless condition. Predisposing factors include smoking, xerostomia (dry mouth), soft diet, poor oral hygiene and certain medications. Management is facilitated by improving oral hygiene, especially scraping or brushing the tongue. Signs and symptoms
Hairy tongue largely occurs in the central part of the dorsal tongue, just anterior (in front) of the circumvallate papillae, although sometimes the entire dorsal surface may be involved. Discoloration usually accompanies hairy tongue, and may be yellow, brown or black. Apart from the appearance, the condition is typically asymptomatic, but sometimes people may experience a gagging sensation or a bad taste. There may also be associated oral malodor (intra-oral halitosis).The term "melanoglossia is also used to refer to there being black discolorations on the tongue without "hairs", which are also harmless and unrelated to black hairy tongue. Causes
The cause is uncertain, but it is thought to be caused by accumulation of epithelial squames and proliferation of chromogenic (i.e., color-producing) microorganisms. There may be an increase in keratin production or a decrease in normal desquamation (shedding of surface epithelial cells). Many people with BHT are heavy smokers. Other possible associated factors are poor oral hygiene, general debilitation, hyposalivation (i.e., decreased salivary flow rate), radiotherapy, overgrowth of fungal or bacterial organisms, and a soft diet.
Socket expansion through the use of implants of increasing size is another effective strategy.After socket expansion is complete, a painted prosthetic eye can be worn for cosmetic reasons. If the microphthalmic eye has functional vision, an affected individual may opt against wearing a painted prothesis. Lenses are also sometimes used for cosmetic purposes, such as a plus lens to enlarge the microphthalmic eye. Epidemiology
Microphthalmia and anophthalmia combined are estimated to occur in about 1 in 10,000 births, though estimates have varied from 2 and 23 in 100,000 births. Approximately 3–11% of all blind children born globally have microphthalmia. See also
References
Further reading
GeneReviews/NCBI/NIH/UW entry on Anophthalmia / Microphthalmia Overview
GeneReviews/NCBI/NIH/UW entry on Microphthalmia with Linear Skin Defects Syndrome
OMIM-Online Mendelian Inheritance in Man


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