[Alexander's disease in an adult].

A 34-year-old man developed cerebellar symptoms, palatal myoclonus and spastic paraparesis progressing over several months. During this period, acute respiratory failure occurred in two instances with evidence of central chronic hypoventilation. CT scan showed enlargement of the frontal horns and posterior fossa cisterns. Post mortem examination revealed the following features: 1) Rosenthal's fibers widespread throughout the CNS but especially in subependymal regions; 2) bilateral white matter cavitations involving the frontal lobes, hilum of dentate nuclei and bulbar pyramids; 3) microscopic pseudogliomatous foci present in several sites, especially in the fornix and midbrain tegmentum; 4) the medulla and high cervical spinal cord showed "peripheral type" myelin fibers along with Schwann cell proliferation in aberrant intra-parenchymal situation. The relationship of this case--as well as the few previous adult reports--to the well-defined infantile Alexander's disease is discussed. The possible hamartomatous nature of both glial changes and aberrant myelin production is emphasized. These various lesions, including Rosenthal fiber formation, are assumed to result from a similar--probably dysontogenetic--pathophysiological mechanism. It is suggested that Alexander's disease, in this case, should be classified among phakomatoses rather than enzymopathic leukodystrophies.