TDO syndrome

TDO Syndrome is a Rare Genetic Condition That Most Often Affects

  • Hair (tricho),
  • Teeth (dento) and
  • Bone (osseous).

The severity is variable and the following features may be present or not.

Head and Neck

  • Head may be elongated front to back.
  • Facial frontal bossing (may have a prominent, protruding forehead that’s also often associated with a heavy brow ridge)


  • Thin and/or pitted enamel (common feature)
  • Small, widely spaced teeth
  • Enlarged pulp chambers and taurodontism. Taurodontism is a condition found of molar teeth whereby the body of the tooth and pulp chamber is elongated vertically at the expense of the roots.
  • Periapical abscesses (A collection of pus, usually caused by an infection that has spread from a tooth to the surrounding tissues.)

Skin, Nails, Hair

  • Brittle nails
  • Kinky hair in most newborns that becomes straight in about 50% of cases during childhood


  • Increased bone density, mild-moderate (skull, spine, long bones)
  • Skull: abnormal shape of the calvaria (skullcap), that part of the skull that is made up of the superior portions of the frontal bone, occipital bone, and parietal bones and covers the cranial cavity that contains the brain.
  • Poorly pneumatized mastoids (associated with eustachian tube dysfunction)

Diagnosing TDO Syndrome

A physician can diagnose tricho-dento-osseous syndrome on the basis of physical features. Symptoms to look for in children:

  • Abnormal teeth
  • Abnormal nails
  • Abnormal hair
  • Skeletal manifestations 

Causes of TDO Syndrome

TDO is caused by a change in the DLX3 gene on chromosome 17q21. A parent may pass the gene to a child. Or, the gene can change in a child without either parent having the changed TDO gene themselves.

Genetic Testing

Testing is available for TDO syndrome.

TDO Inheritance

Tricho-dento-osseous syndrome is inherited as an autosomal dominant disorder. An affected individual has a 50% chance of passing the gene to a son or daughter.

Learn more about TDO syndrome at Online Mendelian Inheritance in Man.