Microcephaly with chorioretinopathy (OMIM 156590) is an autosomal dominant syndrome, characterized primarily by chorioretinal lesions and microcephaly. The phenotype is variable, and has been described in association with retinal dysplasia that can be stable or show progressive degeneration, retinal folds, lymphedema, and mental retardation. We describe two siblings with microcephaly, mental retardation, and variable retinal and choroidal abnormalities. Patient 1 has multiple atrophic and dysplastic‐appearing lesions of the retina and choroid in each eye. An ERG at 5 months of age disclosed markedly subnormal scotopic and photopic responses with delayed flicker timing. Patient 2 has bilateral macular folds with vitreoretinopathy, serous retinal detachments, glaucoma, and cataracts OU. Both have mental retardation with hypotonia and severe microcephaly. Chorioretinopathy and retinal folds have been described independently in microcephaly with chorioretinopathy. The present sibs are the first in whom these features are observed while the parents are normal. Our findings support an expansion of the ocular phenotype and suggest the existence of germ line mosaicism. © 2007 Wiley‐Liss, Inc.