Hydrolethalus syndrome

Last revised by David Luong on 24 Jun 2021

Hydrolethalus syndrome is a rare lethal genetic syndrome characterized by multiple developmental defects of the fetus which include:


The estimated incidence is at approximately 1 in 20000 births. There is often ancestral links to an area in eastern Finland where the syndrome was described, for the first time, in 1981. Outside of this subgroup, the incidence is even much more rarer.



An autosomal recessive inheritance pattern is often suspected and it is thought to be caused by a missense mutation in a novel gene HYLS1.


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