The hydrolethalus syndrome is an autosomal recessive malformation syndrome which has been recently described in Finland. The name hydrolethalus refers to the main findings, namely polyhydramnios, hydrocephalus and lethality. The patients are either stillborn or die soon after birth. The typical roentgenologic findings are hypoplasia of the tibia associated with the anomalies of the respective bone ray, e.g. metatarsus primus varus atavisticus, hallux varus or hallux duplex varus and hydrocephalus with extreme micrognathia and a specific midline defect of the occipital bone.