Hydrolethalus syndrome 1 is a genetic disorder that is caused by a mutation in the HYLS1 gene. A change (mutation) in the gene causes it to not work properly. Each person has two copies of every gene, one from the mother and one from the father. Hydrolethalus syndrome 1 is passed down from parent to child in an autosomal recessive manner, meaning one mutation from each parent is inherited by a child in order to cause symptoms.
Symptoms of hydrolethalus syndrome 1 include extra fingers and toes as well as birth defects such as brain defects, spine defects, spinal cord defects, heart defects, buildup of cerebrospinal fluid in the brain, large or small head size, and premature birth. Diagnosis often occurs during pregnancy with an ultrasound, physical examinations, brain imaging, autopsy, or genetic tests. Hydrolethalus syndrome 1 is more common in people of Finnish descent.
There is currently no definitive treatment, and stillbirth or neonatal death is common. If your baby or a family member has been diagnosed with hydrolethalus syndrome 1, talk with your doctor about the most current treatment options as well as signs that you may need immediate medical attention.