Because the cause of facial clefts still is unclear, it is difficult to say what may prevent children being born with facial clefts. It seems that folic acid contributes to lowering the risk of a child being born with a facial cleft.

The prevalence has been estimated at 1 in 10,000 births, but exact values are hard to know because some that have the symptoms rarely have Pierre-Robin sequence (without any other associated malformation).

Macroglossia is uncommon, and usually occurs in children. Macroglossia has been reported to have a positive family history in 6% of cases. The National Organization of Rare Disorders lists macroglossia as a rare disease (less than 200 000 individuals in the US).

Tongue lesions are very common. For example, in the United States one estimated point prevalence was 15.5% in adults. Tongue lesions are more common in persons who wear dentures and tobacco users. The most common tongue conditions are geographic tongue, followed by fissured tongue and hairy tongue.

It is a relatively common condition, with an estimated prevalence of 6.8%–11% amongst children. Males are more commonly affected. The condition may be seen at any age, but generally affects older people more frequently. The condition also generally becomes more accentuated with age. The prevalence of the condition increases significantly with age, occurring in 40% of the population after the age of 40.

The cause is unknown, but it may be partly a genetic trait. Aging and environmental factors may also contribute to the appearance.

In traditional Chinese medicine, scalloping of the tongue is said to indicate qi vacuity. In some homeopathic sources, scalloping of the tongue is said to be indicative of high blood pressure.

Hypoglossia is a short, incompletely developed tongue. It can occur either as an isolated malformation or in association with other deformities, particularly limb defects in a syndrome known as "oromandibular limb hypogenesis syndrome".

Macroglossia may be caused by a wide variety of congenital and acquired conditions. Isolated macroglossia has no determinable cause. The most common causes of tongue enlargement are vascular malformations (e.g. lymphangioma or hemangioma) and muscular hypertrophy (e.g. Beckwith–Wiedemann syndrome or hemihyperplasia). Enlargement due to lymphangioma gives the tongue a pebbly appearance with multiple superficial dilated lymphatic channels. Enlargement due to hemihyperplasia is unilateral. In edentulous persons, a lack of teeth leaves more room for the tongue to expand into laterally, which can create problems with wearing dentures and may cause pseudomacroglossia.

Amyloidosis is an accumulation of insoluble proteins in tissues that impedes normal function. This can be a cause of macroglossia if amyloid is deposited in the tissues of the tongue, which gives it a nodular appearance. Beckwith–Wiedemann syndrome is a rare hereditary condition, which may include other defects such as omphalocele, visceromegaly, gigantism or neonatal hypoglycemia.

The tongue may show a diffuse, smooth generalized enlargement. The face may show maxillary hypoplasia causing relative mandibular prognathism. Apparent macroglossia can also occur in Down syndrome. The tongue has a papillary, fissured surface. Macroglossia may be a sign of hypothyroid disorders.

Other causes include mucopolysaccharidosis, neurofibromatosis, multiple endocrine neoplasia type 2B, myxedema, acromegaly, angioedema, tumors (e.g. carcinoma), Glycogen storage disease type 2, Simpson-Golabi-Behmel syndrome, Triploid Syndrome, trisomy 4p, fucosidosis, alpha-mannosidosis, Klippel-Trenaunay-Weber syndrome, cardiofaciocutaneous syndrome, Ras pathway disorders, transient neonatal diabetes, and lingual thyroid.

The nose anomalies found in facial clefts vary. The main goal of the treatment is to reconstruct the nose to get a functional and esthetic acceptable result. A few possible treatment options are to reconstruct the nose with a forehead flap or reconstruct the nasal dorsum with a bone graft, for example a rib graft. The nasal reconstruction with a forehead flap is based on the repositioning of a skin flap from the forehead to the nose. A possible downside of this reconstruction is that once you performed it at a younger age, you can’t lengthen the flap at a later stage. A second operation is often needed if the operation is done on early age, because the nose has a restricted growth in the cleft area. Repair of the ala (wing of the nose) often requires the inset of cartilage graft, commonly taken from the ear.

Children affected with PRS usually reach full development and size. However, it has been found internationally that children with PRS are often slightly below average size, raising concerns of incomplete development due to chronic hypoxia related to upper airway obstruction as well as lack of nutrition due to early feeding difficulties or the development of an oral aversion. However, the general prognosis is quite good once the initial breathing and feeding difficulties are overcome in infancy. Most PRS babies grow to lead a healthy and normal adult life.

The most important medical problems are difficulties in breathing and feeding. Affected infants very often need assistance with feeding, for example needing to stay in a lateral(on the side) or prone(on the tummy) position which helps bring the tongue forward and opens up the airway. Babies with a cleft palate will need a special cleft feeding device (such as the Haberman Feeder). Infants who are unable to take in enough calories by mouth to ensure growth may need supplementation with a nasogastric tube. This is related to the difficulty in forming a vacuum in the oral cavity related to the cleft palate, as well as to breathing difficulty related to the posterior position of the tongue. Given the breathing difficulties that some babies with PRS face, they may require more calories to grow (as working of breathing is somewhat like exercising for an infant). Infants, when moderately to severely affected, may occasionally need nasopharyngeal cannulation, or placement of a nasopharyngeal tube to bypass the airway obstruction at the base of the tongue. in some places, children are discharged home with a nasopharyngeal tube for a period of time, and parents are taught how to maintain the tube. Sometimes endotracheal intubation or tracheostomy may be indicated to overcome upper respiratory obstruction. In some centers, a tongue lip adhesion is performed to bring the tongue forward, effectively opening up the airway. Mandibular distraction can be effective by moving the jaw forward to overcome the upper airway obstruction caused by the posterior positioning of the tongue.

Given that a proportion of children with Robin sequence will have Stickler syndrome, it is important that a child with PRS have an evaluation by an optometrist or ophthalmologist in the first year of life looking for myopia that can be seen in Stickler syndrome. Because retinal detachment that can occur in Stickler syndrome is a leading cause of blindness in children, it is very important to recognize and be thoughtful of this diagnosis.

Behavior therapy is important especially when the kids are in their primary dentition in the pre-adolescent age. Improving habits at this time may lead to self-correction of open bite in many cases. Sometimes presence of infantile swallowing into early childhood may lead to an anterior open bite in patients. Habit control through appliances such as Tongue crib or Tongue spurs may be used in adolescent ages if the behavior modification fails to stop the habit.

Glossoptosis is a medical condition and abnormality which involves the downward displacement or retraction of the tongue. It may cause non-fusion of the hard palate causing cleft palate.

It is one of the features of Pierre Robin sequence and Down syndrome.

Examples of congenital disorders which affect the tongue include:

- Aglossia - complete absence of the tongue at birth

- Ankyloglossia (tongue tie) - where the lingual frenum tethers the tongue to the floor of the mouth. If it interferes with oral hygiene and feeding, frenectomy may be indicated.

- Hypoglossia - congenitally short tongue

- Microglossia

- Macroglossia - an abnormally large tongue, seen in some disorders such as Down syndrome (although macroglossia can be an acquired condition as well).

- Hamartomata - for example Leiomyomatous hamartoma

- Glossoptosis

- Choristomata - For example, osseous choristoma of the tongue, a very rare condition characterized by a nodule on the dorsum of the tongue containing mature lamellar bone without osteoblastic or osteoclastic activity. Cartilagenous (chondroid), and glial choristomas may also very rarely occur on the tongue.

- Lingual thyroid

- Cleft tongue (bifid tongue) - completely cleft tongue is a rare condition caused by a failure of the lateral lingual swellings to merge. More common is an incompletely cleft tongue, appearing as midline fissure. This is normally classed as fissured tongue.

Opinion varies regarding how frequently ankyloglossia truly causes problems. Some professionals believe it is rarely symptomatic, whereas others believe it is associated with a variety of problems. The disagreement among professionals was documented in a study by Messner and Lalakea (2000). The authors sent a survey to a total of 1598 otolaryngologists, pediatricians, speech-language pathologists and lactation consultants with questions to ascertain their beliefs on ankyloglossia. 797 of the surveys were fully completed and used in the study. It was found that 69% of lactation consultants, but only a minority of pediatricians answered that ankyloglossia is frequently associated with feeding difficulties; 60% of otolaryngologists and 50% of speech pathologists answered that ankyloglossia is sometimes associated with speech difficulties compared to only 23% of pediatricians; 67% of otolaryngologists compared with 21% of pediatricians answered that ankyloglossia is sometimes associated with social and mechanical difficulties. Limitations of this study include a reduced sample size due to unreturned or incomplete surveys.

Ankyloglossia can affect eating, speech, and oral hygiene as well as have mechanical/social effects. Ankyloglossia can also prevent the tongue from contacting the anterior palate. This can then promote an infantile swallow and hamper the progression to an adult-like swallow which can result in an open bite deformity. It can also result in mandibular prognathism; this happens when the tongue contacts the anterior portion of the mandible with exaggerated anterior thrusts.

Crenated tongue (also called scalloped tongue, pie crust tongue, lingua indentata, or crenulated tongue) is a descriptive term for the appearance of the tongue when there are indentations along the lateral borders (the sides), as the result of compression of the tongue against the adjacent teeth.

The oral mucosa in the area of crenation is usually of normal color, but there may be erythema (redness) if exposed to a high degree of friction or pressure. Crenated tongue is usually asymptomatic and harmless.

It is not a disease as such, but usually results from habits where the tongue is pressed against the lingual surfaces (the side facing the tongue) of the dental arches, or from any cause of macroglossia (enlarged tongue), which in itself has many causes such as Down syndrome.

Where crenation is caused by parafunctional habits, there may also be associated bruxism, linea alba, or morsicatio buccarum.

Factors that can contribute to tongue thrusting include macroglossia (enlarged tongue), thumb sucking, large tonsils, hereditary factors, ankyloglossia (tongue tie), and certain types of artificial nipples used in feeding infants, also allergies or nasal congestion can cause the tongue to lie low in the mouth because of breathing obstruction and finally contributing to tongue thrusting. In addition, it is also seen after prolonged therapy by levodopa in Parkinsonism, also it occurs as extra pyramidal side effect (Acute muscular dystonia) after use of Neuroleptics (Anti-Psychotics).

An anterior open bite occurs in humans when the front teeth fail to touch and there is no overlap between upper incisors and lower incisors. Anterior open can be caused by functional habits such as digit sucking, tongue thrust or long-term pacifier use. When digit sucking habit is present in the late primary to early mixed dentition stages, it can lead to different side-effects such as upper teeth flaring out, lower teeth flaring in, increase in the open bite and the overjet. A posterior crossbite in these children along with decrease in intercanine and intermolar width is also found. The more intense (longer) the habit, the worse the malocclusion may be.

Pacifier use has also shown to cause anterior open bites in children. Pacifier use which lasts longer than 18 months, may cause this malocclusion. It is shown that as long as the sucking habit stops before the eruption of permanent teeth, the open bite self-corrects. In some cases, behavior modification may be necessary to eliminate the dental habits. If all else fails, then a tongue crib can be used.

Tongue thrust is normal in infants until approximately the age of six months. The loss of this normal infant behavior is one of the signs that the baby is ready to begin eating baby food.

Tongue thrusting can adversely affect the teeth and mouth. A person swallows from 1,200 to 2,000 times every 24 hours with about four pounds (1.8 kg) of pressure each time. If a person suffers from tongue thrusting, this continuous pressure tends to force the teeth out of alignment. Many people who tongue thrust have open bites; the force of the tongue against the teeth is an important factor in contributing to "bad bite" (malocclusion). Many orthodontists have completed dental treatment with what appeared to be good results, only to discover that the case relapsed because of the patient's tongue thrust. If the tongue is allowed to continue its pushing action against the teeth, it will continue to push the teeth forward and reverse the orthodontic work.

Speech is not frequently affected by the tongue thrust swallowing pattern. The "S" sound (lisping) is the one most affected. The lateral lisp (air forced on the side of the tongue rather than forward) shows dramatic improvement when the tongue thrust is corrected. However, lisping and tongue thrust are not always associated.

The adaptation from nasal to mouth breathing takes pace when changes such as chronic middle ear infections, sinusitis, allergic rhinitis, upper airway infections, and sleep disturbances (e.g., snoring) take place. In addition, mouth breathing is often associated with a decrease in oxygen intake into the lungs. Mouth breathing can particularly affect the growing face, as the abnormal pull of these muscle groups on facial bones slowly deforms these bones, causing misalignment. The earlier in life these changes take place, the greater the alterations in facial growth, and ultimately an open mouth posture is created where the upper lip is raised and the lower jaw is maintained in an open posture. The tongue, which is normally tucked under the roof of the mouth, drops to the floor of the mouth and protrudes to allow a greater volume of air intake. Consequently, an open mouth posture can lead to malocclusions and problems in swallowing. Other causes of open-mouth posture are weakness of lip muscles, overall lack of tone in the body or hypotonia, and prolonged/chronic allergies of the respiratory tract. A.union

Orofacial myofunctional disorders (OMD) (sometimes called “oral myofunctional disorder", and “tongue thrust”) are muscle disorders of the face, mouth, lips, or jaw.

Recent studies on incidence and prevalence of tongue thrust behaviors are not available. However, according to the previous research, 38% of various populations have OMD. The incidence is as high as 81% in children exhibiting speech/articulation problems (Kellum, 1992).

This phenomenon is fairly common, with one in every 800 adults showing evidence of active lesions at any one time. It is more common in people who are experiencing stress or psychological conditions. The prevalence in females is double the prevalence in males, and it is two or three times more prevalent in people over the age of thirty-five.

Hanhart syndrome (also known as Aglossia adactylia; Hypoglossia-hypodactylia syndrome; Peromelia with micrognathia) is a congenital disorder that causes an undeveloped tongue and malformed extremities and fingers.

Minor physical anomalies (MPAs) are relatively minor (typically painless and, in themselves, harmless) congenital physical abnormalities consisting of features such as low-set ears, single transverse palmar crease, telecanthus, micrognathism, macrocephaly, hypotonia and furrowed tongue. While MPAs may have a genetic basis, they might also be caused by factors in the fetal environment: anoxia, bleeding, or infection. MPAs have been linked to disorders of pregnancy and are thought by some to be a marker for insults to the fetal neural development towards the end of the first trimester. Thus, in the neurodevelopmental literature, they are seen as indirect indications of inferferences with brain development.

MPAs have been studied in autism, Down syndrome, and in schizophrenia. A 2008 meta-analysis found that MPAs are significantly increased in the autistic population. A 1998 study found that 60% of its schizophrenic sample and 38% of their siblings had 6 or more MPAs (especially in the craniofacial area), while only 5% of the control group showed that many.

The most often cited MPA, high arched palate, is described in articles as a microform of a cleft palate. Cleft palates are partly attributable to hypoxia. The vaulted palate caused by nasal obstruction and consequent mouth breathing, without the lateralising effect of the tongue, can produce hypoxia at night.

Other MPAs are reported only sporadically. Capillary malformation is induced by RASA1 mutation and can be changed by hypoxia. A study in the American Journal of Psychiatry by Trixler et al.: found hemangiomas to be highly significant in schizophrenia. Exotropia is reported as having low correlation and high significance as well. It can be caused by perinatal hypoxia.