All the teeth are smaller than the normal size. True generalized microdontia is very rare, and occurs in pituitary dwarfism. Due to decreased levels of growth hormone the teeth fail to develop to a normal size.

Males tend to have larger teeth than females, and tooth size also varies according race. Abnormal tooth size is defined by some as when the dimensions are more than 2 standard deviations from the average. Microdontia is when the teeth are abnormally small, and macrodontia is when the teeth are abnormally large.

All teeth, although the same size, grow in larger than normal. This is seen in cases of growth hormone excess called pituitary gigantism. It is the rarest of the types.

A single tooth is larger than the rest. This is unusual and could be the result of fusion and germination that cause enlarged crowns.

Abnormal development of the skeletal portions of the second arch

1. Nondifferentiation of the stapes, with resultant absence of round and oval window.

2. Abnormal course of the facial nerve.

Skull base abnormalities

1. Hypoplasia of the petrous temporal bone.

2. Hypoplastic and sclerotic petrous apex may mimic labyrinthitis ossificans.

3. Platybasia.

4. Aberrant course of jugular veins.

Michel aplasia, also known as complete labyrinthine aplasia (CLA), is a congenital abnormality of the inner ear. It is characterized by the bilateral absence of differentiated inner ear structures and results in complete deafness (anacusis).

Michel aplasia should not be confused with michel dysplasia. It may affect one or both ears.

"Aplasia" is the medical term for body parts that are absent or do not develop properly. In Michel aplasia, the undeveloped (anaplastic) body part is the bony labyrinth of the inner ear. Other nearby structures may be underdeveloped as well.

These symptoms were found in rare cases of Larsen syndrome.

- Cataracts

- Cleft palate

- Extra bones of wrist

- Malocclusion

- Microdontia and hypodontia

- Complete agenesis of anus

- uterus

- Bifid tongue

Symptoms are related to defects in connective tissue.

- Congenital anterior dislocation of the knees

- Dislocation of hips and shoulders

- Flattened facial appearance

- Prominent forehead

- Depressed nasal bridge

- Club foot

- Cervical kyphosis

These are pleomorphic and include

- dolichocephaly (with or without sagittal suture synostosis)

- microcephaly

- pre- and postnatal growth retardation

- brachydactyly

- narrow thorax

- rhizomelic dwarfism

- epicanthal folds

- hypodontia and/or microdontia

- sparse, slow-growing, hyperpigmented, fine hair

- nail dysplasia

- hypohydrosis

- chronic renal failure

- heart defects

- liver fibrosis

- visual deficits

- photophobia

- hypoplasia of the posterior corpus callosum

- aberrant calcium homeostasis

Electroretinography shows gross abnormalities.

Two fetuses of 19 and 23 weeks gestation have also been reported. They showed acromesomelic shortening, craniofacial characteristics with absence of craniosynostosis, small kidneys with tubular and glomerular microscopic cysts, persistent ductal plate with portal fibrosis in the liver, small adrenals, an enlarged cisterna magna and a posterior fossa cyst.

Sensenbrenner syndrome (OMIM #218330) is a rare (less than 20 cases reported by 2010) multisystem disease first described in 1975. It is inherited in an autosomal recessive fashion, and a number of genes appear to be responsible. Three genes responsible have been identified: intraflagellar transport (IFT)122 (WDR10), IFT43 — a subunit of the IFT complex A machinery of primary cilia, and WDR35 (IFT121: TULP4)

It is also known as Sensenbrenner–Dorst–Owens syndrome, Levin Syndrome I and cranioectodermal dysplasia (CED)

The symptoms of CANDLE syndrome can manifest themselves in a variety of different ways and combinations related to skin disorders, internal inflammatory responses, and fever-based conditions. The types of outwardly visible conditions involve facies not matching other known disorders, contracture of the joints, and skin lesions appearing across any part of the body. The multiple inflammatory developments include nonspecific lymphadenopathy, hepatosplenomegaly, and autoimmune hemolytic anemia. Other possible conditions are hypertriglyceridemia and lipodystrophy.

Other novel mutations resulting in the syndrome have also involved the manifestation of other conditions, such as Sweet's syndrome and pericarditis. Another case in 2015 showcased previously undescribed dental symptoms, such as microdontia and osteopenia of the jaw, along with a general case of diabetes mellitus.

Chronic Atypical Neutrophilic Dermatosis with Lipodystrophy and Elevated Temperature (CANDLE) syndrome is an autosomal recessive disorder that presents itself via various autoinflammatory responses throughout the body, multiple types of skin lesions, and recurrent long-term fever symptoms. The current known cause for the disorder is a mutation in the PSMB8 gene or mutations in other closely related genes. The syndrome was first named and classified in March 2010 after four patients were reviewed with similar symptoms. There have been approximately 30 cases ever reported in the scientific literature, as of 2015.