Reconciling genotype with phenotype: Lessons learned on the Arabian Peninsula.

On the Arabian Peninsula, where consanguineous/endogamous marriages are customary, hereditary eye disease is often autosomal recessive and genotype-phenotype correlation is typically straightforward. However, this is not always the case. Lessons I have learned in the course of reconciling genotype with phenotype in the region include the following: (1) although autosomal recessive disease is common, autosomal dominant disease still occurs; (2) an individual or family can be affected by more than one genetic eye disease; and (3) phenotype trumps genotype.