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TNXB gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

TNXB gene

The TNXB gene provides instructions for creating the tenascin-X protein, which is vital for maintaining the structure and elasticity of connective tissues throughout the body.

Normal Function

The TNXB gene provides instructions for making a protein called tenascin-X. This protein plays a critical role in organizing and maintaining connective tissues that support muscles, joints, organs, and skin. Tenascin-X helps regulate the production and assembly of collagens, which strengthen connective tissues, and it also regulates the structure and stability of elastic fibers that provide flexibility and stretchiness.

Health Conditions Related to Genetic Changes

Ehlers-Danlos syndrome

Mutations in the TNXB gene are associated with specific forms of Ehlers-Danlos syndrome, a group of disorders affecting connective tissues. These include:

  • Hypermobile type: Mutations in one copy of the TNXB gene reduce the amount of functional tenascin-X, weakening connective tissues and leading to an unusually large range of joint movement (hypermobility).
  • Classical-like type: Mutations in both copies of the TNXB gene prevent the production of any tenascin-X protein. This leads to severe disruption of collagen and elastic fibers, resulting in hypermobility and skin that is soft, highly stretchy, and fragile.

Additionally, some individuals with benign joint hypermobility syndrome (BJHS)—a condition characterized by chronic joint pain and hypermobility—also show reduced levels of tenascin-X, though no specific TNXB mutations have been identified in these cases. Research suggests BJHS and the hypermobile type of Ehlers-Danlos syndrome may be forms of the same condition.

Other Names for This Gene

  • hexabrachion-like
  • HXBL
  • tenascin XB1
  • tenascin XB2
  • TENX
  • TENX_HUMAN
  • TNX
  • TNXB1
  • TNXB2
  • TNXBS
  • XB
  • XBS

Frequently Asked Questions

Yes. A tailored program emphasizing low‑impact strengthening, proprioceptive training, and controlled stretching can improve joint stability and decrease pain. Core stabilization and scapular‑control exercises are especially beneficial. It’s important to avoid high‑velocity or extreme‑range movements that may overstretch lax ligaments. Working with a therapist experienced in hypermobility‑type EDS yields the best outcomes.
Pregnancy is generally possible, but increased ligamentous laxity can exacerbate joint pain and predispose to pelvic instability. Close monitoring by a multidisciplinary team (maternal‑fetal medicine, genetics, physiotherapy) is advised. For delivery, many clinicians recommend a planned vaginal birth with pelvic support or, if significant instability exists, a cesarean section to reduce the risk of perineal trauma. Post‑partum physiotherapy helps restore core strength and manage lingering hypermobility symptoms.
heterozygous mutation usually reduces tenascin‑X levels, leading to milder hypermobility, joint pain, and occasional skin laxity (often classified as hypermobile Ehlers‑Danlos or benign joint hypermobility syndrome). Homozygous or compound‑heterozygous loss‑of‑function mutations eliminate functional tenascin‑X, producing the classical‑like EDS phenotype with pronounced skin extensibility, easy bruising, severe joint instability, and a higher risk of chronic musculoskeletal complications.
Diagnosis combines a detailed physical exam (Beighton score for joint hypermobility, skin extensibility assessment) with molecular testing. Sequencing of the TNXB gene (including copy‑number analysis) confirms pathogenic variants. In some centers, serum tenascin‑X levels are measured as a supportive biomarker, but genetic confirmation remains the gold standard.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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