Microcephalic osteodysplastic primordial dwarfism (MOPD) is defined as a syndrome presenting with intrauterine and postnatal growth retardation, typical facial appearance, skeletal dysplasia and brain abnormalities. Autosomal-recessive inheritance is suspected. Sharing clinical manifestations, the former type III has been accepted to be the same entity as type I. We present the case of a male infant with MOPD I and micrencephaly with simplified gyral pattern to a degree defining it as microlissencephaly (MLIS). The brain abnormalities in MOPD I have not yet been classified. Reviewing the literature, we conclude that microlissencephaly appears to be the distinct developmental brain abnormality in MOPD I. Conversely, osteodysplastic changes have to be taken into consideration in the differential diagnosis of microlissencephaly. In addition, our patient suffered from acute lymphatic leukaemia which has not previously been described in association with MOPD I.