Disease Information for Lissencephaly/Norman Roberts (7q22)Miller-Dieker (17p13.3)

under construction gene locus 7q22;LISSENCEPHALY SYNDROME : Clinical Synopsis; Neuro : Lissencephaly, type I ; Thick cerebral cortex ;HEENT :Microcephaly ; Low, sloping forehead; Prominent nasal bridge; Lab : Normal chromosomes ; Inheritance : Autosomal recessive;the disorder can be caused by mutations in the gene encoding reelin.;Type I lissencephaly is characterized by microcephaly and a thickened cortex with 4 rather than 6 layers.; This disorder has forehead and a prominent nasal bridge, features not seen in the Miller-Dieker syndrome (type II) Furthermore, chromosomes are normal whereas in the latter syndrome an abnormality of 17p13 has been found. (Norman-Roberts type)

Multiple affected sibs and parental consanguinity have been observed.; Described a 7-year-old boy with microcephaly, bitemporal hollowing, low sloping forehead, slightly prominent occiput, widely set eyes, broad and prominent nasal bridge, and severe postnatal growth deficiency. Neurologic features included hypertonia, hyperreflexia, seizures, and profound mental retardation. Brain MRI showed changes consistent with lissencephaly type I, grade 2. Molecular studies did not demonstrate deletion in the Miller-Dieker/isolated lissencephaly critical region on 17p; an autosomal recessive form of lissencephaly associated with severe abnormalities of the cerebellum, hippocampus, and brainstem. The disorder mapped to 7q22, and mutations were identified in the RELN gene. Two consanguineous pedigrees were studied. The first consisted head normal head size, congenital lymphedema, and hypotonia. Brain magnetic resonance imaging showed moderate lissencephaly and profound cerebellar hypoplasia. Cognitive development was delayed, with little or no language and no ability to sit or stand unsupported. There was also myopia, nystagmus, and generalized seizures; Also severe delay in neurologic and cognitive development, hypotonia, and epilepsy; With Norman-Roberts syndrome [SubSet]. Both patients had typical craniofacial abnormalities and abnormal magnetic resonance imaging findings, but no deletion in 17p13.3, typical of Miller-Dieker syndrome ;[OMIM Nov 2004]

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