| Disease Association
|| Defects in MYH8 are a cause of trismus- pseudocamptodactyly syndrome (MIM:158300); also called Hecht-Beals or Dutch-Kentucky syndrome. The trismus-pseudocamptodactyly syndrome is a hereditary distal arthrogryposis characterized by an inability to open the mouth fully (trismus) and pseudocamptodactyly in which wrist dorsiflexion, but not volarflexion, produces involuntary flexion contracture of distal and proximal interphalangeal joints. Such hand and jaw contractures are caused by shortened flexor muscle-tendon units. Similar lower-limb contractures also produce foot deformity. The trismus-pseudocamptodactyly syndrome is a morbid autosomal dominant trait with variable expressivity but high penetrance. In these patients, trismus complicates dental care, feeding during infancy, and intubation for anesthesia, and the pseudocamptodactyly impairs manual dexterity, with consequent occupational and social disability. Many patients require surgical correction of contractures.