Which are the causes of Arthrogryposis?

TL;DR: Arthrogryposis, or Arthrogryposis Multiplex Congenita (AMC), is not a single disease but a clinical finding characterized by multiple joint contractures present at birth, caused by any condition that limits fetal movement in the womb. Its causes are diverse and complex, ranging from genetic mutations affecting muscle or nerve development to physical constraints in the uterus that prevent normal fetal positioning.

What are the primary causes of Arthrogryposis?

At its core, Arthrogryposis occurs because of fetal akinesia—a decrease or total lack of movement during development. In a healthy pregnancy, fetal movement is essential for the proper formation of joints and the surrounding soft tissues. If the fetus cannot move, the tissues around the joints shorten and harden, leading to the permanent contractures seen in Arthrogryposis. Think of it like a hinge that becomes stuck because it has not been opened or closed for a long time; the body essentially "locks" the joint in place due to lack of use during critical growth windows.

Is Arthrogryposis hereditary or genetic?

The genetic landscape of Arthrogryposis is highly heterogeneous. While many cases occur sporadically (meaning they are not inherited from parents), others are linked to specific genetic mutations. Researchers have identified over 400 different conditions that can present with Arthrogryposis symptoms. These genetic factors often fall into the following categories:

• Neuropathic causes: Mutations affecting the development of motor neurons, which prevent the brain from sending the necessary signals to muscles to move.


• Myopathic causes: Genetic defects directly within the muscle tissue that prevent the muscles from responding to nerve signals.


• Connective tissue disorders: Genetic abnormalities that affect the structural integrity of tendons, ligaments, and joint capsules.

Are there environmental or physical risk factors?

Beyond genetics, external factors can contribute to the development of Arthrogryposis. Physical constraints within the uterus are a significant cause. If there is not enough room for the fetus to move, the joints can become fixed. Examples include:

• Oligohydramnios: A condition where there is an insufficient amount of amniotic fluid, which acts as a cushion and allows for movement.


• Uterine malformations: Abnormal shapes of the uterus that physically crowd the fetus.


• Maternal illness: Certain infections or metabolic conditions in the mother can indirectly impact fetal development, though these are less common than structural causes.

Is the cause of Arthrogryposis fully understood?

While we understand the mechanism of fetal akinesia, the underlying etiology for every individual remains a subject of intense research. For many patients, especially those in the DiseaseMaps.org community, identifying the exact "cause" can be a long diagnostic journey. Currently, researchers are utilizing advanced genomic sequencing, such as Whole Exome Sequencing (WES), to identify rare mutations that were previously undetectable. This research is vital because understanding whether the cause is primarily neurological, muscular, or environmental helps clinicians provide more targeted physical therapy and surgical interventions for Arthrogryposis patients.

Next steps

• Consult with a clinical geneticist to discuss potential underlying causes through genetic testing.


• Schedule an evaluation with a pediatric orthopedist or a physical medicine and rehabilitation (physiatrist) specialist.


• Connect with the 383 members of the DiseaseMaps.org community to share experiences and coping strategies for managing joint and limb health.


• Keep a detailed medical diary of joint range-of-motion changes to assist your care team in tracking disease progression.

Medical disclaimer: This information is for educational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Arthrogryposis Multiplex Congenita.


• Orphanet: Arthrogryposis multiplex congenita (ORPHA:93245).


• OMIM (Online Mendelian Inheritance in Man): Database entries for various forms of Arthrogryposis.


• Arthrogryposis Group (Patient Advocacy Foundation).