In this paper we report a 7-month-old boy with lobar holoprosencephaly in whom midline interhemispheric fusion occurred between thickened gyri cinguli of both hemispheres at the middle frontal region. This anomaly appears to be a variation of a recently recognized type of holoprosencephaly associated with midline interhemispheric fusion and atypical callosal dysgenesis. In contrast to the previously reported a few cases, in our patient the corpus callosum was thinned but intact. In addition, the condition was associated with diffuse cortical dysplasia. The malformations in this patient is of interest because it contributes to our understanding of variations of holoprosencephaly.