Aspartylglucosaminuria (McKusick 208400) is a lysosomopathy associated with aspartylglucosaminidase (L-aspartamido-beta-N-acetylglucosamine amidohydrolase, EC 3.5.1.26) deficiency. It has been most frequently encountered in Finland, where the regional incidence may be as high as 1 in 3600 births. In