The customary classification of the amaurotic family idiocies according to the time of life at which neurological signs first appear has obvious limitations when consideration is given to cases occupying an intermediate position between the well-established infantile form of Tay-Sachs' and the juvenile form first described by Batten (1903). It was to this group of atypical cases that Bielschowsky (1913–14, 1920) gave the name “late infantile”. This term is convenient clinically but when more examples of the variant had been reported it became evident that the group of cases so designated was not homogeneous. Wyburn-Mason (1943) was able to show in a large clinical material that many of these intermediate forms belonged either to families affected by Tay-Sachs' or by Batten's disease and that in an individual case the ophthalmological findings were usually of decisive importance in classification. The existence of a precocious variant of the classical “juvenile” type of amaurotic idiocy was thus clearly established. Klenk's (1939) discovery that the nerve cells in Tay-Sachs' disease contain large amounts of a glycolipid subsequently called “ganglioside” has provided a further valuable criterion in distinguishing this form of lipidosis from other members of the group. The present case, an example of the precocious juvenile type of amaurotic idiocy or, as we prefer to name it, the subacute form of Batten's disease, is presented as a further contribution to this subject.
A "G" to "A" mutation at position -1 of a 5' splice site in a late infantile form of Tay-Sachs disease.