Organ growth in Rett syndrome: A postmortem examination analysis

Rett syndrome is a disorder of unknown etiology in females that manifests a s severe mental and motor retardation during the first years of life. A pos tnatal pattern of altered growth is its earliest clinical expression. Head growth decelerates during the first year of age and is followed by a declin e in somatic (height/ weight) growth. The decreased occipitofrontal circumf erence (OFC) is reflected in decreased brain size, and measurements of the dendrites of cortical neurons suggest that a developmental and growth arres t have occurred. To further document growth in Rett syndrome, measurements of organ weights, as recorded in 39 postmortem examination studies were com pared with normal organ weights for females of comparable age and height. T hese organ weights suggest that the pattern of growth failure in Rett syndr ome, as compared with other forms of mental handicap, such as Down syndrome and Turner's syndrome, may be unique. In Rett syndrome the rate of brain g rowth, as derived from OFC, decelerates after birth, The increment in norma l brain weight after 4 years of age, the age of the first postmortem examin ations, is not observed in the Rett brain, The heart, kidneys, liver, and s pleen grow at the normally defined rate until 8-12 years of age, when their growth rate decelerates, but their growth continues achieving organ weight s that are appropriate for the height of the female. Adrenal weights are no rmal. These observations suggest that despite a generalized decreased growt h in Rett syndrome the brain may be preferentially affected in this syndrom e. (C) 1999 by Elsevier Science Inc. All rights reserved.