What are the other Names for this Condition? (Also known as/Synonyms)

• DD (Diastrophic Dysplasia)
• Diastrophic Dwarfism
• Diastrophic Nanism Syndrome

What is Diastrophic Dysplasia? (Definition/Background Information)

• Diastrophic Dysplasia is an autosomal recessive genetic disorder characterized by decreased limb length and several bone abnormalities. Most of the presentations are apparent at birth (congenital) or observed pre-parturition with imaging scans (i.e., during the final pregnancy stages)
• Having a positive family history for Diastrophic Dysplasia is a risk factor for the same. It is believed to be caused by an abnormality in a gene known as DTDST on chromosome 5. The most prominent signs and symptoms noted are shortened limbs and malformation of hands, feet, and head bones
• The treatment may involve managing the signs and symptoms via physical therapy, use of prosthetic aids, and surgery, as needed. The prognosis for Diastrophic Dysplasia is generally favorable for cases that do not present severe complications

Who gets Diastrophic Dysplasia? (Age and Sex Distribution)

• The signs and symptoms of Diastrophic Dysplasia have a congenital manifestation (apparent at birth) and affect individuals throughout their lives
• Both males and females can be affected
• All races and ethnic groups are affected, though it is slightly higher among Caucasians (especially in the country of Finland)

What are the Risk Factors for Diastrophic Dysplasia? (Predisposing Factors)

Predisposing factors for Diastrophic Dysplasia include:

• Having a parent or both parents with Diastrophic Dysplasia, as it is inherited as an autosomal recessive trait
• Having parents that are closely blood-related (consanguineous)

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others. 

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Diastrophic Dysplasia? (Etiology)

Diastrophic Dysplasia is an inherited genetic disorder.

• It is believed to be an autosomal recessive disorder caused by an abnormality in a gene known as DTDST (diastrophic dysplasia sulphate transporter gene) located on the long arm of chromosome 5
• This causes abnormalities in the formation of cartilage and therefore affecting the development of the skeletal structure of the fetus
  • During the development of the embryo, the skeleton consists primarily of cartilage which will later become bone
  • The resulting skeletal structure will have a distribution of cartilage cells that is abnormal

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Diastrophic Dysplasia?

The signs and symptoms of Diastrophic Dysplasia may vary from one individual to another and can be mild or severe. It may include:

• Delayed growth of the long bones (arms and legs) known as epiphyses
• Thumbs may be small, oval-shaped, and stick away from the body (hitchhiker’s thumb)
• Fingers may be short (brachydactyly) and the joints may fuse (symphalangism)
• Wrist bones may be deformed
• Foot deformities (talipes) including:
  • Heels point outward (talipes valgus) or inward (talipes equinovarus)
  • Front of foot points inward (metatarsus adductus)
  • Flexed soles of the feet (talipes equinus)
  • Big toe may point away from the body
• Partial or complete dislocation of joints such as the knee. These dislocations can also occur in the lower vertebrae
• Abnormally loose or stiff elbows or knees
• Degenerative changes in joints that can lead to severe pain
• Incomplete vertebral closure or narrowing of portions of the vertebrae in the lower back
• Cysts in the ears of newborn
• Hearing problems due to abnormal formation of the three bones (auditory ossicles) of the middle ear which project sound to the inner ear
• Cranial deformations such as:
  • Bulging forehead
  • Small jaw
  • Cleft palate which can lead to difficulties eating and breathing
  • Narrowing or collapse of trachea (windpipe), larynx (voice box), or bronchi (passage to lungs)
• Nasal voice
• Dental malformations such as:
  • Small teeth
  • Dental crowding
• Red/purple growths on midline of face; abnormal blood vessel formation

How is Diastrophic Dysplasia Diagnosed?

A diagnosis of Diastrophic Dysplasia is made by the following observations and tests:

• A careful physical examination and evaluation of a patient’s medical history
• Assessment of the presenting signs and symptoms
• Following birth, X-rays, CT, or MRI scan studies may be used to study the bone abnormalities (i.e., short fingers, arms, or legs etc.)
• Genetic testing can be performed to diagnose Diastrophic Dysplasia as early as the first trimester of pregnancy
• Diastrophic Dysplasia may be diagnosed by fetal ultrasound as early as the second trimester

Many clinical conditions can have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Diastrophic Dysplasia?

The possible complications of Diastrophic Dysplasia include:

• Decreased mobility due to bone development abnormalities
• Abnormal sideways spinal curvature (scoliosis) or front back curvature (kyphosis). These may lead to:
  • Respiratory problems
  • Spinal compression
  • Muscular weakness due to nerve damage (paresis)
  • Paralysis
• Reduced hearing
• Dental abnormalities which can make eating difficult
• Emotional stress and decreased quality of life
• Treatment complications

How is Diastrophic Dysplasia Treated?

The treatments for Diastrophic Dysplasia are directed towards managing the signs and symptoms and may include:

• Use of hearing aids, if required
• Physical therapy to improve mobility
• Development of motor skills via daily exercises,
• Use of walking aids including foot orthotics and special footwear
• Surgeries to repair developmental abnormalities such as cleft palate or spinal malformations which result in respiratory difficulties
• Ongoing monitoring of abnormal front-back spinal curvature (kyphosis) that may worsen over time
• Use of braces
• Occupational therapy and rehabilitation

Regular medical screening at periodic intervals with tests and physical examinations are necessary and highly recommended.

How can Diastrophic Dysplasia be Prevented?

Diastrophic Dysplasia may not be preventable since many of these genetic disorders are diagnosed at or following the birth of the child.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

What is the Prognosis of Diastrophic Dysplasia? (Outcomes/Resolutions)

The prognosis for Diastrophic Dysplasia is generally positive, and most affected individuals can lead healthy fulfilling lives.

• Diastrophic Dysplasia, however, increases perinatal mortality by about 5%, due to respiratory problems or cervical myelopathy
• A lethal form of Diastrophic Dysplasia exists and may cause death soon after birth from cardiorespiratory insufficiency

Additional and Relevant Useful Information for Diastrophic Dysplasia:

Physical therapy has been found to have a beneficial effect on walking despite conditions such as talipes or “clubfeet.”