Rare Primary Care News

Disease Profile

Tricho-dento-osseous syndrome

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

<1 / 1 000 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

TDO syndrome; Enamel hypoplasia and hypocalcification with associated strikingly curly hair


Congenital and Genetic Diseases; Mouth Diseases; Musculoskeletal Diseases;


The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 3352

Tricho-dento-osseous dysplasia (TDO) belongs to the ectodermal dysplasias and is characterised by curly/kinky hair at birth, enamel hypoplasia with discolouration and molar taurodontism, increased overall bone mineral density (BMD) and increased thickness of the cortical bones of the skull.

The prevalence is unknown but the disease has been described in at least 8 families with over 30 affected members in some large kindreds.

Clinical description
The disease shows significant inter and intrafamilial clinical variation, with enamel hypoplasia and taurodontism being the most consistent features, however, the extent of the enamel defects may also vary between affected family members. The hair and bone manifestations are more variable and age dependent. Curly/kinky hair is present at birth in around 80% of patients, but around half of these patients loose the hair phenotype by adolescence. The BMD measurements show increasing variability with age, particularly in the radius and ulna. In addition, spinal BMD shows an increase with age. Other reported features include flat/brittle fingernails, increased susceptibility for caries and abscesses, delayed dental eruption, tubular sclerosis of the long bones, dolichocephaly (as a result of craniosynostosis), and an absence of mastoid pneumatisation, the frontal sinus and calvarial diploe.

The syndrome is caused by mutations in the distal-less homeobox gene (DLX3), located on the long arm of chromosome 17 (17q21.3-q22).

Diagnostic methods
Diagnosis can be made by clinical and radiological examination and confirmed by detection of DLX3 mutations.

Differential diagnosis
The differential diagnosis should include amelogenesis imperfecta, hypomaturation-hypoplastic type, with taurodontism (AIHHT), oculodentoosseous dysplasia (see this term) and the autosomal dominant form of osteopetrosis (see this term).

Genetic counseling
The disease is transmitted as a highly penetrant autosomal dominant trait.

Management and treatment
Treatment is symptomatic and patients require frequent dental follow-up.

The prognosis is good and there appearsto be no predisposition for developing fractures.

Visit the Orphanet disease page for more resources.


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
30%-79% of people have these symptoms
Abnormal hair quantity
Abnormality of the mastoid
Dental enamel pits
Pitting of tooth enamel
Tooth enamel pits

[ more ]

Long, narrow head
Tall and narrow skull

[ more ]

Fragile nails
Brittle nails
Frontal bossing
Hypomineralization of enamel
Poorly mineralized tooth enamel
Increased bone mineral density
Increased bone density
Decreased width of tooth
Obliteration of the calvarial diploe
Periapical tooth abscess
Widely spaced teeth
Wide-spaced teeth
Widely-spaced teeth

[ more ]

5%-29% of people have these symptoms
Agenesis of incisor
Finger clinodactyly
Percent of people who have these symptoms is not available through HPO
Abnormal hair morphology
Abnormality of the hair
Hair abnormality

[ more ]

Autosomal dominant inheritance


Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Tricho-dento-osseous syndrome. Click on the link to view a sample search on this topic.