Trismus-Pseudocamptodactyly Syndrome

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Trismus-pseudocamptodactyly syndrome


Trismus-pseudocamptodactyly syndrome is a rare genetic condition characterized by the inability to completely open the mouth (trismus), difficulty chewing, short stature, and abnormally short muscle-tendon units in the fingers that cause the fingers to curve or bend when the hand is bent back at the wrist (pseudocamptodactyly).


Trismus-pseudocamptodactyly syndrome was first described by the pediatrician/geneticist Frederick Hecht and the orthopedist Rodney K. Beals of the Oregon Health Sciences University in 1969 as inability-to-open-the-mouth-fully syndrome. Explaining the first descriptive name for the syndrome, individuals affected by trismus-pseudocamptodactyly syndrome cannot fully open the mouth (trismus). In addition, affected individuals are unable to bend their fingers when their wrist is extended (pseudocamptodactyly). The muscles and tendons in the forearms and/or the legs may also be abnormally short, resulting in limited movements and various deformities of the feet, including clubfoot , hammer and claw toes, and tightening of the muscles of the posterior part of the leg, producing other multiple foot abnormalities. The severity of the physical findings in trismus-pseudocamptodactyly syndrome varies from individual to individual.

Trismus-pseudocamptodactyly syndrome is also known as inability-to-open-the-mouth-fully syndrome, Dutch-Kennedy syndrome, camptodactyly-limited jaw excursion, Hecht syndrome, inability to open mouth completely and short finger-flexor, Hecht-Beals-Wilson syndrome, distal arthrogryposis, and Hecht-Beals syndrome.

Genetic profile

Trismus-pseudocamptodactyly syndrome is a rare condition inherited in an autosomal dominant pattern. In an autosomal dominant condition, only one copy of the mutated, or nonworking, gene for a particular condition is necessary for a person to experience the symptoms associated with the condition. Accordingly, most individuals with an autosomal dominant condition have one working copy and one nonworking copy of the gene for the disorder. Individuals contribute only half of their genetic information to their children and pass on only one copy of each gene. As a result, there is a 50% chance for a person with trismus-pseudocamptodactyly syndrome to pass on the nonworking gene for that condition and have a child affected with trismus-pseudocamptodactyly syndrome. There is also a 50% chance that a person with trismus-pseudocamptodactyly syndrome will pass on the working gene and have a child unaffected by trismus-pseudocamptodactyly syndrome. Individuals in the same family who inherit a copy of the nonworking copy of the gene causing trismus-pseudocamptodactyly syndrome can be affected in different manners and with different symptoms. Symptoms of trismus-pseudocamptodactyly syndrome present in a variety of mild to severe features (variable expressivity). However, in trismus-pseudocamptodactyly syndrome, a high percentage of individuals who inherit the abnormal gene will have some sign of the disorder (high penetrance).

The genetic cause of trismus-pseudocamptodactyly syndrome is not yet fully understood. In 2004, several families with members affected by complex variant conditions associated with trismus pseudocamptodactyly were examined, and it was determined that affected members of two families had a mutation in the MYH8 gene (perinatal myosin heavy-chain gene) on the short arm of chromosome 17 (17q13.1). The same mutation was also identified in affected members of a large Caucasian Belgian family affected by trismus-pseudocamptodactyly syndrome alone. Based on these studies, it appears that many cases of trismus-pseudocamptodactyly syndrome are caused by a mutation in MYH8; however, it is still unclear if trismus-pseudocamptodactyly syndrome is caused by mutations in other genes as well.


Trismus-pseudocamptodactyly syndrome is a rare condition affecting both men and women equally. It was originally described in a Dutch family and believed to only occur in Dutch families or the descendants of Dutch families in West Virginia. Since the original families were identified, families of other ethnic backgrounds, including Canadians, Taiwanese, and Japanese, have been found to be affected. Accordingly, it is believed that trismus-pseudocamptodactyly syndrome can occur in any race or ethnic background.

Signs and symptoms

Individuals affected by trismus-pseudocamptodactyly syndrome classically present with two main features: limited excursion of the mandible (trismus) and flexion deformity of the fingers that occurs with wrist extension (pseudocamptodactyly). At birth, trismus-pseudocamptodactyly syndrome may be diagnosed based on the infant's clenched fists and inability to fully open its mouth. Additional features include short stature and foot malformations caused by short muscle-tendon units, which prevent normal growth and development. The forms of foot abnormalities caused by short muscle-tendons in the hamstrings, calves, and feet include malformations that occur when the foot is turned inward and downward (equinovarus or talipes equinovarus), inward bending for the front half of the foot (metatarsus varus), and angling foot at the heel with the toes pointing upward and outward (calcaneovalgus deformity). Different family members who have inherited the same mutated, or nonworking, gene can have symptoms that range from very mild to very severe.


Diagnosis of trismus-pseudocamptodactyly syndrome is made through a detailed physical exam, medical history, and family history most often performed by a medical genetics team. Clinical genetic testing is not available at this time; however, research testing for MYH8 at 17p13.1 may be available through a genetic clinic.

Treatment and management

The treatment and management of trismus-pseudocamptodactyly syndrome depends on the severity of the symptoms. Most individuals are treated with a combination of physical therapy, speech therapy, occupational therapy, and surgery.

An infant's inability to fully open its mouth can cause severe difficulties with feeding, adequate calorie intake, speech development, and dental care. Speech and physical therapy are recommended to help address jaw issues. Jaw surgery may be necessary to open infants' jaws for nourishment. The clenched fists found in many infants affected by trismus-pseudocamptodactyly syndrome can cause difficulties in learning to crawl and grasp items. Often infants will learn to crawl on their knuckles. The clenched fists involved with pseudocamptodactyly may also impair manual dexterity and cause occupational disability that requires physical and occupational therapy or surgery. Contractures due to the short muscle-tendons may result in foot abnormalities that, like clenched fists, may delay milestones. Affected infants may require surgical correction of contractures and foot abnormalities in order to walk.

Adults affected by trismus-pseudocamptodactyly syndrome continue to have issues with inability to open their mouths fully, short muscle-tendons, and foot anomalies. Although many individuals pursue surgical options, there is no consensus on the optimal treatment. In one report, endoscopic surgery to release the jaw in one patient resulted in recurrence three months postoperatively. Another technique that had some success was a passive stretching of the mouth with tongue blades. Early treatment of trismus can prevent or minimize many of the conditions. Passive motion, applied several times per day, has been shown to be more effective than static stretching for keeping short muscle-tendons supple. Recent research has shown that passive motion provides significant reduction in inflammation and pain. Ongoing physical therapy and stretching of contractures caused by short muscle-tendons may help maintain optimal muscle length over time, allowing improved range of motion and preventing relapse after surgery.

General anesthesia and muscle relaxants do not relieve the trismus or increase the jaw's opening. Since an open mouth is necessary to intubate in the traditional manner, general anesthesia for any surgery can be difficult and hazardous. Several reports on intubation techniques are found in the anesthesia literature that recommend techniques, such as avoiding muscle relaxants and using fiberoptic-assisted nasotracheal intubation, blind nasotracheal intubation, or mask anesthesia with spontaneous ventilation to assess the delivery of anesthesia and surgery. During all surgical procedures, it is recommended that a surgeon experienced in obtaining an emergency surgical airway be available.


Most individuals with trismus-pseudocamptodactyly syndrome can achieve a mouth opening large enough for food and speech and a sufficient range of motion in their affected joints to live healthy, complete lives. In many individuals, physical therapy and stretching of contractures caused by short muscle-tendons may help maintain optimal muscle length, allowing improved range of motion and quality of life. However, the severe contractures and pseudocamptodactyly that appear in some individuals affected by trismus-pseudocamptodactyly syndrome may impair manual dexterity and cause occupational disability that places physical restrictions.



Lefaivre, J. F., and M. J. Aitchison. "Surgical Correction of Trismus in a Child with Hecht Syndrome." Ann Plast Surg. 2003 Mar; 50 (3): 310–4.


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Genetic Alliance. 4301 Connecticut Avenue NW, Washington, DC 20008-2304. (202) 966-5557, (800) 336-4363. E-mail: [email protected]

National Institute of Arthritis and Musculoskeletal and Skin Diseases. 1 AMS Circle, Bethesda, MD 20892-3675. (301) 496-8188, (877) 226-4267. E-mail: [email protected] (April 13, 2005.) <>.


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Dawn Jacob Laney