Fraser syndrome 1 is caused by homozygous or heterozygous mutations in the FRAS1 gene (4q21.21).
Fraser syndrome 2 (617666) results from homozygous mutations in the FREM2 gene (13q13.3). Parental consanguinity is common (25%) and familial patterns are consistent with autosomal recessive inheritance.
Fraser syndrome 3 (617667) results from homozygous mutations in the GRIP1 gene (12q14.3). Three consanguineous families have been reported.
Mutations in GRIP1 (PAD14) (12q14.3) have also been found in 3 families in which the parents were consanguineous.
Isolated cryptophthalmos (123570) also occurs in autosomal dominant pedigrees as well as sporadically. It is rarely found as an incidental feature of other syndromes.