Paula and Bobby
Parents of Lillie
Arthrogryposis, Distal, Type 8 (DA8)
What is Arthrogryposis, Distal, Type 8 (DA8)?
Also known as Arthrogryposis, Distal, Type 8, this very rare genetic condition has been identified in just 50 people to date.
The syndrome is part of a group of disorders that present with multiple congenital contractures, which make it difficult for individuals to move specific parts of their body.
This syndrome is also known as:
Multiple Pterygium Syndrome; Autosomal Dominant Pterygium Syndrome; Multiple, Autosomal Dominant
What gene changes cause Arthrogryposis, Distal, Type 8 (DA8)?
Mutations to the CHRNG gene are responsible for causing the syndrome. It is mainly inherited in an autosomal recessive pattern, but there have been cases of it being passed in an autosomal dominant pattern.
Autosomal recessive inheritance means an affected individual receives one copy of a mutated gene from each of their parents, giving them two copies of a mutated gene. Parents, who carry only one copy of the gene mutation will not generally show any symptoms, but have a 25% chance of passing the copies of the gene mutations onto each of their children.
In the case of autosomal dominant inheritance just one parent is the carrier of the gene mutation, and they have a 50% chance of passing it onto each of their children. Syndromes inherited in an autosomal dominant inheritance are caused by just one copy of the gene mutation.
What are the main symptoms of Arthrogryposis, Distal, Type 8 (DA8)?
Two major symptoms usually present before birth: webbing of the skin between the joints, and a lack of muscle movement.
Unique facial features of the syndrome include a small jaw, long philtrum, downward slanting eyes, epicanthal folds, drooping eyelids, low set ears and a cleft palate.
The condition also presents with a small stature, defects in the vertebrae, contractures of the joints, webbing of the neck, permanently bent fingers, webbing between the fingers and club feet.
Curvature of the spine and skeletal anomalies are also common. All of these physical features may also affect movement.
Possible clinical traits/features:
Cleft palate, Short stature, Hemivertebrae, Hip contracture, Elbow flexion contracture, Craniosynostosis, Arthrogryposis multiplex congenita, Downslanted palpebral fissures, Autosomal dominant inheritance, Short neck, Low-set, posteriorly rotated ears, Knee flexion contracture, Multiple pterygia, Camptodactyly, Scoliosis, Spondylolisthesis, Vertebral fusion, Ptosis
How does someone get tested for Arthrogryposis, Distal, Type 8 (DA8)?
The initial testing for Multiple Pterygium syndrome can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow.
Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.
Medical information on Arthrogryposis, Distal, Type 8 (DA8)
Frias et al., (1973) described a family with an autosomal dominant form of multiple pterygium syndrome. The family described by Kawira et al., (1985) may be similar. The features are ptosis, an antimongoloid eye slant, pterygia of the neck, knees and elbows, camptodactyly and scoliosis. Radiographs may reveal vertebral anomalies such as vertebral fusion or hemivertebrae, fusion of carpals and tarsals and pelvic dysplasia.
McKeown and Harris (1988) reported a similar family where a mother and three children were affected. The most severely affected member had features of classical multiple pterygium syndrome, but other family members had milder features of the condition including ptosis, posteriorly rotated ears, webbing of the neck, axilla, elbow, or knees, and vertebral anomalies. Short stature and mental retardation appeared to be a feature of the condition in this family. A mildly affected father and his daughter were reported by Prontera et al., (2006). It was uncertain whether this was dominant or whether he was an expressing heterozygote of recessive disease.
Members from 3 families with dominant multiple ptrygium syndrome were found to have mutations in MYH3 (Chong et al., 2015). Mutations were in the tail domain whereas MYH3 mutations known to cause DA1, 2A and 2B occur in the head and neck domain
* This information is courtesy of the L M D.
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