Morphologic and histoanatomic observations of the brain in untreated human phenylketonuria.

The cerebra of three profoundly retarded adult males with untreated phenylketonuria (PKU) were systematically studied in terms of developmental morphology and histoanatomy against normal age-matched material, technically comparable in preparation. These studies were made possible by the availability of two extensive reference collections of normative neuroanatomic material, the Yakovlev and the Conel collections. The developmental parameters of myelination, width of the cortical plate, cell packing density, neuronal cell size, development of Nissl granulation, dendritic arborization and synaptic spine populations were studied. Our results indicate that there is a marked curtailment of histoanatomical maturation of the brain in PKU by all developmental parameters studied.