This report describes general characteristics of the group of diseases classified as primary microcephaly (MCPH). Primary microcephaly is a genetically heterogeneous disorder, with multiple genes and mapped loci. A listing of MCPH subtypes, as defined by OMIM, can be found in the table below, with links to more detailed reports for subtypes that have been investigated using fly models.
[updated June 2016 by FlyBase; FBrf0222196]
Primary microcephaly (MCPH) refers to the clinical finding of a head circumference less than 3 standard deviations below the age- and sex-related mean, present at birth. Primary microcephaly is a static developmental anomaly, distinguished from secondary microcephaly, which refers to a progressive neurodegenerative condition. Microcephaly is a disorder of fetal brain growth; individuals with microcephaly have small brains and almost always have mental retardation; additional clinical features may include short stature or mild seizures (review by Woods et al., 2005; pubmed:15806441). [from MIM:251200; 2016.06.16]
Genetically heterogenous; most cases of primary microcephaly show an autosomal recessive mode of inheritance.
MCPH is associated with a simplification of the cerebral cortical gyral pattern and a slight reduction in the volume of the white matter, consistent with the small size of the brain, but the architecture of the brain in general is normal, with no evidence of a neuronal migration defect (review by Woods et al., 2005; pubmed:15806441). [from MIM:251200; 2016.06.16]
