Hydrolethalus Syndrome (HYLS1)
Hydrolethalus syndrome is an autosomal recessive disorder caused by pathogenic variants in the gene HYLS1 and is most commonly found among those of Finnish descent. Affected individuals often present with polydactyly and central nervous system malformations, a small jaw, poorly formed nose and eyes, and cardiac and respiratory defects. The pregnancy itself can be characterized by an excess of amniotic fluid, intrauterine growth restriction, and preterm delivery. The majority of affected infants are stillborn or will die shortly after birth due to the many congenital malformations and organ defects. Early detection of the syndrome can be possible via ultrasound. To date, all patients identified have had the same pathogenic variant.
For information about carrier frequency and residual risk, please see the residual risk table.