At the present time three types of amaurotic family idiocy are generally recognized: the infantile, with onset of the disease under 1 year; the juvenile, with onset between 6 and 14 years, and the late form, occurring in adult life. In addition, a few cases have been reported with age incidence between 1 and 5 years and termed, accordingly, "late infantile" cases. Features such as the protracted course, the absence of macular changes and the occurrence of cerebellar atrophy have been considered characteristic of this type.
The present study reports a new case of "late infantile" amaurotic idiocy. The clinical report may be of interest because of the extreme enlargement of the head. The pathologic examination showed certain unusual features that bring to the fore the question of the relationship of amaurotic idiocy to familial diffuse sclerosis. Moreover, special attention was directed to the investigation of the chemical nature of