• Disease Overview
  • Synonyms
  • Signs & Symptoms
  • Causes
  • Affected Populations
  • Disorders with Similar Symptoms
  • Diagnosis
  • Standard Therapies
  • Clinical Trials and Studies
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  • Complete Report

Trismus-Pseudocamptodactyly Syndrome


Last updated: August 07, 2019
Years published: 1992, 1996, 1997, 1998, 1999, 2003, 2019


NORD gratefully acknowledges Roa Sadat, MMSc, NORD Editorial Intern from the Emory University Genetic Counseling Training Program and Cecelia A. Bellcross, PhD, MS, CGC, Associate Professor, Director, Genetic Counseling Training Program, Emory University School of Medicine, for assistance in the preparation of this report.

Disease Overview


Trismus-pseudocamptodactyly syndrome (TPS) is a rare inherited disorder characterized by short muscles and tendons that result in limited mobility of the hands, legs, and mouth. The most serious complication of this condition is the inability to completely open the mouth (trismus), which causes difficulty with chewing. Short muscles and tendons in the fingers cause the fingers to bend or curve (camptodactyly) when the hand is bent back at the wrist. However, the fingers are not permanently bent or curved, so this particular finding is called “pseudocamptodactyly” (pseudo meaning false). This condition can also result in limited movement and various malformations of the feet. Many of the symptoms of TPS manifest during infancy. As an affected child ages, abnormalities associated with shortened muscle-tendons units (e.g., difficulty with coordinated hand movements) may become apparent. There is currently no cure for this condition, however, a team of specialist can help treat and manage the symptoms. The severity of these physical findings varies from individual to individual.

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  • TPS
  • camptodactyly-limited jaw excursion
  • Dutch-Kennedy syndrome
  • Hecht syndrome
  • distal arthrogryposis type 7
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Signs & Symptoms

TPS is a rare genetic disorder of muscle development and function. It is characterized by the inability to fully open the mouth (trismus), often resulting in problems with chewing. Although this is one of the most significant findings, it may not be as severe in some affected individuals. In those whom this abnormality is severe, limited and/or impaired chewing may cause difficulties with eating and proper digestion.

Other major physical findings associated with TPS involve the fibrous cords that connect muscles to bones (tendons). Tendons work together with nearby muscles (muscle-tendon unit) and bones to produce movement of various parts of the body. If tendons are unusually short, this may result in certain physical abnormalities. In TPS, the muscle-tendon units in the fingers are unusually short, resulting in curved or bent fingers (camptodactyly) when the hand is bent backward at the wrist. However, if the hand is bent forward at the wrist, the fingers can then be completely extended. The fingers are not permanently fixed in the bent or curved position, therefore this finding is called “pseudocamptodactyly”.

In addition, individuals with this syndrome have shortened muscle-tendon units in the forearms and legs. Short muscle-tendon units in the leg may cause various foot problems. These may include a permanent flexing of the toe or toes (hammer or claw toes), abnormal inward bending of the foot (clubfoot), flatfoot, and/or pigeon-toe. In some cases, shortened muscles and tendons may result in an unusual tilt of the pelvis, which can lead to hip dislocation. Abnormal positioning or slight twist of the head is also seen in some individuals. Many people with TPS often have difficulty with fine motor skills of the hands (i.e. holding small objects) and walking.

Some individuals with TPS may be slightly shorter than would otherwise be expected. Those with TPS have a normal life expectancy and normal intelligence. It is important to note that the severity of the physical findings associated with this disorder may vary from individual to individual.

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TPS is an autosomal dominant disorder caused by changes in the MYH8 gene. All cases of TPS studied to date were found to have the same change in the MYH8 gene. This gene is involved in making the instructions for the development of the limb skeletal muscles and the muscles in the face.

Most genetic diseases are determined by the status of the two copies of a gene, one received from the father and one from the mother. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary to cause a particular disease. The abnormal gene can be inherited from either parent or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from an affected parent to an offspring is 50% for each pregnancy. The risk is the same for males and females.

In some individuals, the disorder is due to a spontaneous (de novo) genetic mutation that occurs in the egg or sperm cell. In such situations, the disorder is not inherited from the parents.

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Affected populations

TPS affects females and males equally. However, twice as many affected females have been reported. The current prevalence rate of TPS is unknown. Approximately 11 families and over 300 individual cases have been reported since the disorder was first described in 1969. Of those cases, some have been traced to a Dutch female who came to the United States and settled in Tennessee during the eighteenth century. In addition, other reported cases have included five affected individuals in three generations of one Japanese family, six affected members of a German family. Affected individuals of families from the Netherlands, Canada, United Kingdom, Belgium, and Taiwan have also been reported.

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TPS may be diagnosed during infancy, based on a thorough clinical evaluation, characteristic physical findings, and/or a variety of specialized tests, including X-rays studies. Individuals with this condition may be born with their hands clenched, but the hands usually loosen shortly after birth.

Genetic testing can be performed to confirm a clinical suspicion of TPS. The identification of one abnormal copy of the MYH8 gene can help confirm a diagnosis of TPS.

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Standard Therapies

The treatment of this disorder is directed toward the specific symptoms seen in each individual. Treatment may require the efforts of a team of specialists who work together to plan a child’s care. Such specialists may include pediatricians, those who diagnose and treat skeletal disorders (orthopedists), orthopedic surgeons, dentists, anesthesiologists, physicians who specialize in disorders of the digestive tract (gastroenterologists), nutritionists, and physical and occupational therapists.

In some people, jaw surgery may be performed to help increase the opening of their mouth.

Genetic counseling is recommended for affected individuals and their families.

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Clinical Trials and Studies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Toll-free: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

Some current clinical trials also are posted on the following page on the NORD website:

For information about clinical trials sponsored by private sources, contact:

For more information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/

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(Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder [e.g., musculoskeletal abnormalities, etc.].)

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Jones KL, ed. Smith’s Recognizable Patterns of Human Malformation. 5th ed. Philadelphia, PA: W. B. Saunders Co: 1997:228.

Buyse ML, ed. Birth Defects Encyclopedia. Dover, MA: Blackwell Scientific Publications; For: The Center for Birth Defects Information Services Inc; 1990:257-58.

Dai, Z., et al. Caution in interpretation of disease causality for heterozygous loss-of-function variants in the MYH8 gene associated with autosomal dominant disorder. Eur J Med Genet. 2017:60(6):312-316.

Gasparini G, Boniello R, Moro A, Zampino G, Pelo S. Trismus-pseudocamptodactyly syndrome: case report ten years after. Eur J Paediatr Dent. 2008;9(4):199-203.

Minzer-conzetti K, Wu E, Vargervik K, Slavotinek A. Phenotypic variation in trismus-pseudocamptodactyly syndrome caused by a recurrent MYH8 mutation. Clin Dysmorphol. 2008;17(1):1-4.

Toydemir RM,Chen H, Proud VK, Martin R, van Bokhon H, Hamel BC, Tuerlings JH, Stratakis CA, Jorde LB, Bamshad MJ. “TPS is caused by a recurrent mutation of MYH8.” AM J Med Genet A. 2006 Oct 13; 140A(22):2387–2393.

Carlos R, Contreras E, Cabrera J. Trismus-pseudocamptodactyly syndrome (Hecht-Beals’ syndrome): case report and literature review. Oral Dis. 2005;11(3):186-9.

Pelo S, Boghi F, Moro A, Boniello R, Mosca R. Trismus-pseudocamptodactyly syndrome: a case report. Eur J Paediatr Dent. 2003 Mar;4(1):33-6.

Lefaivre JF, et al. Surgical correction of trismus in a child with Hecht syndrome. Ann Plast Surg. 2003;50:310-14.

Ishii T. Trismus-pseudocamptodactyly syndrome. Ryoikibetsu Shokogun Shirizu. 2001;(33):314-5.

Seavello J, Hammer GB. Tracheal intubation in a child with trismus pseudocamptodactyly (Hecht) syndrome. J Clin Anesth. 999;11:254-56.

Lano CF Jr, Werkhaven J. Airway management in a patient with Hecht’s syndrome. South Med J. 1997;90:1241-3.

Rombouts JJ, et al. Trismus-pseudocamptodactyly syndrome: presentation and genealogy of a new European case. Ann Chir Main Memb Super.1992;11:333-37.

Hertrich K, et al. Restricted mouth opening as a leading symptom of trismus-pseudocamptodactyly syndrome. Dtsch Zahnarztl Z .1991;46:416-19.

Vaghadia H, et al. Anaesthetic implications of the trismus pseudocamptodactyly (Dutch-Kentucky or Hecht Beals) syndrome. Can J Anaesth.1988;35:80-85.

O’Brien PJ, et al. Orthopaedic aspects of the trismus pseudocamptodactyly syndrome. J Pediatr Orthop.1984;4:469-71.

Robertson RD, et al. Linkage analysis with the trismus-pseudocamptodactyly syndrome. Am J Med Genet.1982;12:115-20.

Mercuri LG. The Hecht, Beals, and Wilson syndrome: report of case. J Oral Surg. 1981;39:53-56.

Yamashita DD, et al. Trismus-pseudocamptodactyly syndrome. J Oral Surg. 1980;38:625-30.

Mabry CC, et al. Trismus pseudocamptodactyly syndrome: Dutch-Kentucky syndrome. J Pediatr.1974;85:503-08.

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