What is the definition of Fetal Akinesia Sequence?
Fetal akinesia deformation sequence (FADS) is a condition characterized by decreased fetal movement (fetal akinesia) as well as intra-uterine growth restriction (IUGR), multiple joint contractures (arthrogryposis), facial anomalies, underdevelopment of the lungs (pulmonary hypoplasia) and other developmental abnormalities. It is generally accepted that this condition is not a true diagnosis or a specific syndrome, but rather a description of a group of abnormalities resulting from fetal akinesia. About 30% of affected individuals are stillborn; many liveborn infants survive only a short time due to complications of pulmonary hypoplasia. FADS may be inherited in an autosomal recessive manner in some cases and may sometimes be caused by mutations in the RAPSN or DOK7 genes.
What are the alternative names for Fetal Akinesia Sequence?
- Fetal akinesia sequence
- Pena-Shokeir syndrome, type 1
- Arthrogryposis multiplex congenita with pulmonary hypoplasia
What are the causes for Fetal Akinesia Sequence?
Many underlying causes of fetal akinesia deformation sequence (FADS) have been recognized including genetic, environmental and maternal factors. The features of the condition are largely due to decreased fetal activity/movement. Failure of normal swallowing results in polyhydramnios (too much amniotic fluid), and lack of movement of the diaphragm and intercostal muscles leads to pulmonary hypoplasia (underdevelopment of the lungs). Lack of normal fetal movement also results in a short umbilical cord and multiple joint contractures.
Possible causes for decreased fetal movement which may contribute to the features of FADS may include:
- Neurologic abnormalities such as cerebral and cerebellar dysgenesis (abnormal development); spinal tract, myelin, and end plate disturbances; and ischemia (deficient blood supply) with secondary loss of neuron function
- Myopathic (muscle-related) abnormalities such as dystrophies and dyplasias
- Connective tissue abnormalities including chondrodysplasias, restrictive skin, and joint limitation or laxity
- Fetal edema for a variety of reasons (storage, metabolic, heart failure, lymphatic dysplasia, etc.)
- Maternal illness, drugs, and antibodies (including maternal myasthenia gravis)
- Ischemic changes during embryonic/fetal development, which may be due to developmental vascular abnormalities, trauma, hypotension, drugs, infections, and maternal illness or thrombophilia
Autosomal recessive inheritance of FADS has been implied in several published cases. Genes in which mutations have been detected in affected individuals include the RAPSN and DOK7 genes. According to current literature, the recurrence risk is estimated to be 10–25%.
How is Fetal Akinesia Sequence diagnosed?
There are quite a few potential underlying causes of fetal akinesia deformation sequence (FADS). Sometimes the cause is unknown, sometimes the cause is known and is not genetic, and other times although a genetic cause may be suspected, genetic testing may not be available. Currently, genetic testing is available for two genes in which mutations have reportedly caused the condition in specific cases.
GeneTests lists the names of the laboratories that are performing genetic testing for FADS. To view the contact information for these laboratories, click on the following links:
DOK7-Related Fetal Akinesia Deformation Sequence
RAPSN-Related Fetal Akinesia Deformation Sequence
Please note that most of the laboratories listed through GeneTests do not accept direct contact from patients and their families; therefore, if you are interested in learning more, you will need to work with a health care provider or a genetics professional.