Thus, RecQ helicases are important for maintaining DNA stability, and loss of function of these helicases has important implications in the development of Werner syndrome. In addition to the central domain, there are three exonuclease domains at the N-terminus and a Helicase and Ribonuclease D C-terminal (HRDC) domain at the C-terminus.When functioning normally, the WRN gene and its associated protein (WRNp) are important for maintaining genome stability. WRNp is active in unwinding DNA, a step necessary in DNA repair and DNA replication. Specifically, it has an important role in responding to replication malfunctions, particularly double-stranded breaks, and stalled replication machinery. WRNp may reactivate replication by preventing unwanted recombination processes from occurring or by promoting recombination, depending on the type of DNA damage. In addition, WRNp physically interacts with or binds to several other proteins that are involved in processing DNA. For example, when WRNp binds to RPA, its helicase activity is stimulated. WRNp also physically interacts with p53, a tumor suppressor gene that stops the formation of tumors and the progression of cancers, which inhibits the exonuclease activity of the WRNp. Since WRNps function depends on DNA, it is only functional when localized to the nucleus.Surprisingly, complete loss of WRN helicase activity does not cause clinical Werner syndrome.
Differential diagnosis are ectopic thyroid, enlarged lymph nodes, dermoid cysts and goiter.Thyroglossal cyst usually presents as a midline neck lump (in the region of the hyoid bone) that is usually painless, smooth and cystic, though if infected, pain can occur. There may be difficulty breathing, dysphagia (difficulty swallowing), or dyspepsia (discomfort in the upper abdomen), especially if the cyst becomes large.The most common location for a thyroglossal cyst is midline or slightly off midline, between the isthmus of the thyroid and the hyoid bone or just above the hyoid bone. A thyroglossal cyst can develop anywhere along a thyroglossal duct, though cysts within the tongue or in the floor of the mouth are rare.A thyroglossal cyst will move upwards with protrusion of the tongue.Thyroglossal cysts are associated with an increased incidence of ectopic thyroid tissue. Occasionally, a lingual thyroid can be seen as a flattened strawberry-like lump at the base of the tongue. Complications
Infection
An infected thyroglossal duct cyst can occur when it is left untreated for a certain amount of time or simply when a thyroglossal duct cyst hasnt been suspected. The degree of infection can be examined as major rim enhancement has occurred, located inferior to the hyoid bone. Soft tissue swelling occurs, along with airway obstruction and trouble swallowing, due to the rapid enlargement of the cyst. With infections, there can be rare cases where an expression of fluid is projected into the pharynx causing other problems within the neck.