A neuropathological study of a case of the Prader-Willi syndrome with an interstitial deletion of the proximal long arm of chromosome 15.

An autopsy case, a 6-month-old girl, with an interstitial deletion of the long arm of chromosome 15;del(15)(q11.1q12) was reported. Muscle hypotonia, poor sucking and intermittent ocular deviation were noticed soon after birth. She also exhibited external features peculiar to the Prader-Willi syndrome (PWS). The muscle hypotonia persisted and head control was not achieved. She died at the age of 6 months due to bronchopneumonia. G-banding analysis of prometaphase chromosomes revealed a deletion of chromosome 15. Bronchopneumonia of the lungs and fatty metamorphosis of the liver were found. Neuropathological anomalies recognized were; disturbed undulating structures, resembling cortical micropolygyria and pachygyria, in the dentate nucleus and the inferior olivary nucleus, grumose degeneration of the nerve cells in the dentate nucleus, and heterotopia of middle-sized neurons in the cerebellar white matter. No abnormalities were observed in the hypothalamus-pituitary system. In some autopsy cases of PWS, cerebellar lesions have been reported. These might be related to the muscle hypotonia in PWS.