Diastrophic Dysplasia

Diastrophic dysplasia, an autosomal recessive disorder related to a mutation in the DTDST gene, is characterized by micromelia, clubfoot hand deformities, multiple joint flexion contractures, and scoliosis. DNA analysis for prenatal diagnosis is possible.

Incidence: Rare.

Sonographic findings:

Fig 1, Fig 2, Fig 3, Fig 4

• Micromelia, typically severe rhizomelic-type limb shortening and bowing of all long bones but a wide spectrum of severity.
• Hand deformities with abducted positions of the thumbs or toes called hitchhiker thumbs and toes which are relatively unique for diastrophic dysplasia; 3D ultrasound may provide better details.
• Long bones are not bowed, unlike most other lethal syndromes.
• Micrognathia, facial clefts and cardiac defects are occasionally seen.
• Differential diagnoses include thanatophoric dysplasia, achondroplasia, arthrogryposis multiple congenita, atelosteosgenesis type II and pseudodiastrophic dysplasia.
• Usually diagnosable in the second trimester, but diagnosis in the late first trimester has been reported.

Fig 1:  Hitchhiker thumbs  Abnormal posture and wide separation of the thumb (arrow) in the fetus with diastrophic dysplasia (25 weeks)

Fig 2:  Shortenings of long bones   Short humerus, ulna and radius but normal bone density in the fetus with diastrophic dysplasia

Fig 3:  Scoliosis  Coronal scan of the spine: scoliosis of thoracic spine in the fetus with diastrophic dysplasia

Fig 4:  Hitchhiker toe  Abnormal posture and wide separation of the toe (arrow) in the fetus with diastrophic dysplasia (26 weeks)

Associations: Rare.

Management: Termination of pregnancy may be an option when diagnosed before viability. For the continuing pregnancy, diastrophic dysplasia should not alter the standard obstetric management.

Recurrence risk: Because it is an autosomal recessive disorder, the theoretical risk of recurrence is 25%.

Prognosis: Non-lethal, normal intellectual development, but a wide spectrum of morbidity.