RAPSN-related disorders are conditions that interrupt the usual communication between nerve cells and muscles. When there are changes (mutations) in the RAPSN, it can lead to two main problems: Congenital Myasthenic Syndrome 11 (CMS 11) and Fetal Akinesia Deformation Sequence (FADS).
CMS 11 is the more common one. Kids with this often get diagnosed at birth or when they’re really young. They might have stiff joints, a weak cry, and problems with breathing. The muscles can be weak, making the baby feel floppy. Feeding can be hard because of weak sucking and low muscle tone. Breathing might be tough, especially when the child is sick. Facial muscles can be weak too, making it hard to keep the eyes open or use them normally. Motor development, like crawling and walking, could be delayed. The symptoms can be different for each person and might get worse with illness or activity. Medication can help manage the symptoms, and machines may be used for breathing difficulties.
FADS is rarer. It causes serious issues before birth, like limited movement, poor growth, lung problems, and facial abnormalities. Many pregnancies with FADS end early or result in stillbirth. Unfortunately, there’s no cure for RAPSN-related disorders. For CMS 11, medicines can sometimes make things better, and machines might help with breathing problems. Physical therapy can be useful for stiff joints. For those with FADS, the treatment focuses on support.
This group of conditions is caused by pathogenic (disease-causing) variants in the RAPSN gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background.