Clinical variability of genetic isolates of Cohen syndrome.

Cohen syndrome (CS) (OMIM#216550) is an uncommon autosomal recessive developmental disorder that has been attributed to mutations in the COH1 gene in at least 200 patients of diverse ethnic background so far. The clinical heterogeneity of CS is evident when comparing patients of different ethnic backgrounds, especially when evaluating specific system phenotypes separately, such as the ophthalmic and central nervous systems. We reviewed the available clinical data on CS cohorts of patients who share a founder effect and demonstrated that most features associated so far with CS are less than those always present in the patients who share a founder mutation thus representing clinical heterogeneity. Furthermore, there is a wide clinical variability of CS in the distinct founder mutation cohorts, the Finnish, Greek/Mediterranean, Amish and Irish travelers. The Greek/Mediterranean founder mutation is correlated to a CS phenotype characterized by specific and persistent skeletal features, corneal changes, periodontal disease, a distinct neurocognitive phenotype for the high recurrence of autism and non-verbal communication and inconstant microcephaly.