This rare genetic disorder is characterized by the webbing of the skin, vertebral defects, facial anomalies and lack of muscle movement. There are two types of this syndrome based on the severity of the symptoms that includes Escobar type which is the milder version and the lethal multiple pterygium syndrome that is considered to be fatal before or very soon after the birth of the infant.
Causes
The mutation identified in the gene known as CHRNG causes most of the multiple pterygium syndrome. This gene produces the gamma (Y) protein component of the acetylcholine receptor protein (AChR) which is detected in the membranes of the skeletal muscle cells. AChr is essential for the normal signaling between the nerves and the muscle cells that is important for the movements. Around the 33rd week of pregnancy, the Y subunit becomes replaced by another subunit so the fetal AChR is replaced by the adult AChR. When the genetic mutation occurs, the Y subunit is either impaired or is missing. The mutation that prevents the production of Y subunit causes the lethal type while its deficit causes the Escobar type. The lacking of the signaling between the nerve and the muscle cells causes this condition. Multiple pterygium syndrome is inherited in an autosomal recessive pattern meaning both the copies of the gene in each cell from the parents are defective.
Symptoms
The symptoms of multiple pterygium syndrome include a short stature, joints that are bent in a fixed position (contractures), webbing of the skin between the fingers (syndactyly), permanently bent fingers, club feet and webbing of the neck, back of the knees and the armpits. The movements of the affected individuals become affected because of the webbing of the skin and contractures of the joints. The facial features include down-slanting eyes, drooping eyelids, low-set ears, a small jaw and cleft palate. The skeletal anomalies include lateral curvature of the spine, rib fusion, abnormal ear bones, malformed kneecaps and spinal fusion abnormalities.
Diagnosis
The diagnosis is possible with the complete physical examination, involving a thorough clinical history and with various tests. To determine the extent of the congenital abnormalities, various imaging tests may be required such as MRI, X-rays and CT scans. Additional tests may also be required to rule out other conditions presenting similar features. The genetic tests can confirm the diagnosis by detecting the genetic mutation responsible for developing this syndrome.
Treatment
The treatment is based on the complexity of the condition and the severity of the organs involved. The affected individuals are at increased risk of developing pneumonia hence respiratory infections should be treated promptly. In the case of webbing, plastic surgery may be required that can improve the fused fingers. An orthopedic specialist should be consulted with as these children can develop scoliosis before the age of five in most cases. Periodic medical follow-up may be required from a multidisciplinary team of specialists as part of the ongoing treatment plan to prevent the development of complications and to monitor the condition. Genetic counseling may be beneficial for the affected individual and their family members.
References
https://ghr.nlm.nih.gov/condition/multiple-pterygium-syndrome#inheritance
https://rarediseases.info.nih.gov/diseases/7111/multiple-pterygium-syndrome-escobar-type
https://rarediseases.org/rare-diseases/pterygium-syndrome-multiple/
