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).

Macroglossia is the medical term for an unusually large tongue. Severe enlargement of the tongue can cause cosmetic and functional difficulties in speaking, eating, swallowing and sleeping. Macroglossia is uncommon, and usually occurs in children. There are many causes. Treatment is dependent upon the exact cause.

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.

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.

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.

Assisted reproductive technology (ART) is a general term referring to methods used to achieve pregnancy by artificial or partially artificial means. According to the CDC, in general, ART procedures involve surgically removing eggs from a woman's ovaries, combining them with sperm in the laboratory, and returning them to the woman's body or donating them to another woman. ART has been associated with epigenetic syndromes, specifically BWS and Angelman syndrome. Three groups have shown an increased rate of ART conception in children with BWS. A retrospective case control study from Australia found a 1 in 4000 risk of BWS in their in-vitro population, several times higher than the general population. Another study found that children conceived by in vitro fertilisation (IVF) are three to four times more likely to develop the condition. No specific type of ART has been more closely associated with BWS. The mechanism by which ART produces this effect is still under investigation.

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.

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.

Beckwith–Wiedemann syndrome has an estimated incidence of one in 13,700; about 300 children with BWS are born each year in the United States. The exact incidence of BWS is unknown because of the marked variability in the syndrome's presentation and difficulties with diagnosis. The number of reported infants born with BWS is most likely low because many are born with BWS, but have clinical features that are less prominent and therefore missed. BWS has been documented in a variety of ethnic groups and occurs equally in males and females.

Children conceived through In vitro fertilization have a three to fourfold increased chance of developing Beckwith–Wiedemann syndrome. It is thought that this is due to genes being turned on or off by the IVF procedures.

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.

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).

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.

Neonatal thyroid screening programs from all over the world have revealed that congenital hypothyroidism (CH) occurs with an incidence of 1:3000 to 1:4000. The differences in CH-incidence are more likely due to iodine deficiency thyroid disorders or to the type of screening method than to ethnic affiliation. CH is caused by an absent or defective thyroid gland classified into agenesis (22-42%), ectopy (35-42%) and gland in place defects (24-36%). It is also found to be of increased association with female sex and gestational age >40 weeks.

Most children born with congenital hypothyroidism and correctly treated with thyroxine grow and develop normally in all respects. Even most of those with athyreosis and undetectable T levels at birth develop with normal intelligence, although as a population academic performance tends to be below that of siblings and mild learning problems occur in some.

Congenital hypothyroidism is the most common preventable cause of intellectual disability. Few treatments in the practice of medicine provide as large a benefit for as small an effort.

The developmental quotient (DQ, as per Gesell Developmental Schedules) of children with hypothyroidism at age 24 months that have received treatment within the first 3 weeks of birth is summarised below:

Several different nutritional deficiency states of vitamins or minerals have been linked to AC. It is thought that in about 25% of people with AC, iron deficiency or deficiency of B vitamins are involved. Nutritional deficiencies may be a more common cause of AC in Third World countries. Chronic iron deficiency may also cause koilonychia (spoon shaped deformity of the fingernails) and glossitis (inflammation of the tongue). It is not completely understood how iron deficiency causes AC, but it is known that it causes a degree of immunocompromise (decreased efficiency of the immune system) which may in turn allow an opportunistic infection of candida. Vitamin B2 deficiency (ariboflavinosis) may also cause AC, and other conditions such as redness of mucous membranes, magenta colored glossitis (pink inflammation of the tongue). Vitamin B5 deficiency may also cause AC, along with glossitis, and skin changes similar to seborrhoeic dermatitis around the eyes, nose and mouth. Vitamin B12 deficiency is sometimes responsible for AC, and commonly occurs together with folate deficiency (a lack of folic acid), which also causes glossitis and megaloblastic anemia. Vitamin B3 deficiency (pellagra) is another possible cause, and in which other association conditions such as dermatitis, diarrhea, dementia and glossitis can occur. Biotin (vitamin B7) deficiency has also been reported to cause AC, along with hair loss (alopecia) and dry eyes. Zinc deficiency is known to cause AC. Other symptoms may include diarrhea, alopecia and dermatitis. Acrodermatitis enteropathica is an autosomal recessive genetic disorder causing impaired absorption of zinc, and is associated with AC.

In general, these nutritional disorders may be caused by malnutrition, such as may occur in alcoholism or in poorly considered diets, or by malabsorption secondary to gastrointestinal disorders (e.g. Coeliac disease or chronic pancreatitis) or gastrointestinal surgeries (e.g. pernicious anemia caused by ileal resection in Crohn's disease).

Some systemic disorders are involved in angular cheilitis by virtue of their association with malabsorption and the creation of nutritional deficiencies described above. Such examples include people with anorexia nervosa. Other disorders may cause lip enlargement (e.g. orofacial granulomatosis), which alters the local anatomy and extenuates the skin folds at the corners of the mouth. More still may be involved because they affect the immune system, allowing normally harmless organisms like Candida to become pathogenic and cause an infection. Xerostomia (dry mouth) is thought to account for about 5% of cases of AC. Xerostomia itself has many possible causes, but commonly the cause may be side effects of medications, or conditions such as Sjögren's syndrome. Conversely, conditions which cause drooling or sialorrhoea (excessive salivation) can cause angular cheilitis by creating a constant wet environment in the corners of the mouth. About 25% of people with Down syndrome appear to have AC. This is due to relative macroglossia, an apparently large tongue in a small mouth, which may constantly stick out of the mouth causing maceration of the corners of the mouth with saliva. Inflammatory bowel diseases (such as Crohn's disease or ulcerative colitis) can be associated with angular cheilitis. In Crohn's, it is likely the result of malabsorption and immunosuppressive therapy which gives rise to the sores at the corner of the mouth. Glucagonomas are rare pancreatic endocrine tumors which secrete glucagon, and cause a syndrome of dermatitis, glucose intolerance, weight loss and anemia. AC is a common feature of glucagonoma syndrome. Infrequently, angular cheilitis may be one of the manifestations of chronic mucocutaneous candidiasis, and sometimes cases of oropharyngeal or esophageal candidiasis may accompany angular cheilitis. Angular cheilitis may be present in human immunodeficiency virus infection, neutropenia, or diabetes. Angular cheilitis is more common in people with eczema because their skin is more sensitive to irritants. Other conditions possibly associated include plasma cell gingivitis, Melkersson-Rosenthal syndrome, or sideropenic dysphagia (also called Plummer-Vinson syndrome or Paterson-Brown-Kelly syndrome).

Pallister-Killian does not appear to be hereditary. Some research has suggested that the presence of the extra chromosome may be linked to premeiotic mitotic errors, both maternally and paternally. Several theories regarding the mechanism of this formation have been introduced.

ICF syndrome (or Immunodeficiency, Centromere instability and Facial anomalies syndrome) is a very rare autosomal recessive immune disorder.

It is characterized by variable reductions in serum immunoglobulin levels which cause most ICF patients to succumb to infectious diseases before adulthood. ICF syndrome patients exhibit facial anomalies which include hypertelorism, low-set ears, epicanthal folds and macroglossia.

Pallister–Killian syndrome (also tetrasomy 12p mosaicism or Pallister mosaic aneuploidy syndrome) is an extremely rare genetic disorder occurring in humans. Pallister-Killian occurs due to the presence of the anomalous extra isochromosome 12p, the short arm of the twelfth chromosome. This leads to the development of tetrasomy 12p. Because not all cells have the extra isochromosome, Pallister-Killian is a mosaic condition (more readily detected in skin fibroblasts).

It was first described by Philip Pallister in 1977 and further researched by Maria Teschler-Nicola and Wolfgang Killian in 1981.

Oral ulceration is a common reason for people to seek medical or dental advice. A breach of the oral mucosa probably affects most people at various times during life. For a discussion of the epidemiology of aphthous stomatitis, see Aphthous stomatitis#Epidemiology.

Many infections can cause oral ulceration (see table). The most common are herpes simplex virus (herpes labialis, primary herpetic gingivostomatitis), varicella zoster (chicken pox, shingles), and coxsackie A virus (hand, foot and mouth disease). Human immunodeficiency virus (HIV) creates immunodeficiencies which allow opportunistic infections or neoplasms to proliferate. Bacterial processes leading to ulceration can be caused by "Mycobacterium tuberculosis" (tuberculosis) and "Treponema pallidum" (syphilis).

Opportunistic activity by combinations of otherwise normal bacterial flora, such as aerobic streptococci, "Neisseria", "Actinomyces", spirochetes, and "Bacteroides" species can prolong the ulcerative process. Fungal causes include "Coccidioides immitis" (valley fever), "Cryptococcus neoformans" (cryptococcosis), and "Blastomyces dermatitidis" ("North American Blastomycosis"). Entamoeba histolytica, a parasitic protozoan, is sometimes known to cause mouth ulcers through formation of cysts.

The GM1 gangliosidoses (or GM1 gangliosidos"i"s) are caused by a deficiency of beta-galactosidase, with resulting abnormal storage of acidic lipid materials in cells of the central and peripheral nervous systems, but particularly in the nerve cells.

GM1 Gangliosidoses are inherited, autosomal recessive sphingolipidoses, resulting from marked deficiency of Acid Beta Galactosidase.

Acromegaly is a disorder that results from excess growth hormone (GH) after the growth plates have closed. The initial symptom is typically enlargement of the hands and feet. There may also be enlargement of the forehead, jaw, and nose. Other symptoms may include joint pain, thicker skin, deepening of the voice, headaches, and problems with vision. Complications of the disease may include type 2 diabetes, sleep apnea, and high blood pressure.

Acromegaly is typically due to the pituitary gland producing too much growth hormone. In more than 95% of cases the excess production is due to a benign tumor, known as a pituitary adenoma. The condition is not inherited from a person's parents. Rarely acromegaly is due to tumors in other parts of the body. Diagnosis is by measuring growth hormone after a person has drunk glucose or by measuring insulin-like growth factor I in the blood. After diagnosis, medical imaging of the pituitary is carried out to look for an adenoma. If excess growth hormone is produced during childhood the result is gigantism.

Treatment options include surgery to remove the tumor, medications, and radiation therapy. Surgery is usually the preferred treatment and is most effective when the tumor is smaller. In those in whom surgery is not effective, medications of the somatostatin analogue or GH receptor antagonist type may be used. The effects of radiation therapy are more gradual than that of surgery or medication. Without treatment those affected live on average 10 years less; however, with treatment life expectancy is typically normal.

Acromegaly affects about 6 per 100,000 people. It is most commonly diagnosed in middle age. Males and females are affected with equal frequency. The first medical description of the disorder occurred in 1772 by Nicolas Saucerotte. The term is from Greek "akron" meaning "extremity" and "mega" meaning "large".

Radiation therapy has been used both as a primary treatment and combined with surgery or drugs. It is usually reserved for patients who have tumor remaining after surgery. These patients often also receive medication to lower GH levels. Radiation therapy is given in divided doses over four to six weeks. This treatment lowers GH levels by about 50 percent over 2 to 5 years. Patients monitored for more than 5 years show significant further improvement. Radiation therapy causes a gradual loss of production of other pituitary hormones with time. Loss of vision and brain injury, which have been reported, are very rare complications of radiation treatments.