Retrospective diagnosis of feline GM2 gangliosidosis variant 0 (Sandhoff-like disease) in Japan: possible spread of the mutant allele in the Japanese domestic cat population.

GM2 gangliosidosis variant 0 (human Sandhoff disease) is a lysosomal storage disease caused by simultaneous deficiencies of acid beta-hexosaminidase (Hex) A and Hex B due to an abnormality of beta-subunit, a common component in these enzyme molecules, which is coded by the HEXB gene. In the present study, a retrospective diagnosis was performed in 2 previous suspected cases of feline Sandhoff-like disease using a DNA test to detect the causative mutation identified previously in 4 cats in 2 other families of Japanese domestic cats. Enzymic analysis was also performed using stored leukocytes and plasma collected from the subject families in order to investigate the usefulness of enzymic diagnosis and genotyping of carriers. The DNA test suggested that the 2 cases were homozygous recessive for the mutation. Consequently, 6 cats homozygous for the same mutation have been found in 4 separate locations of Japan, suggesting that this mutant allele may be spread widely in the Japanese domestic cat populations. In enzymic analysis, Hex A and Hex B activities in leukocytes and plasma measured using 4-methylumbelliferyl N-acetyl-beta-D-glucosaminide as a substrate were negligible in affected cats, compared with those in normal and carrier cats. However, there was a wide overlap in enzyme activity between normal and carrier cats. Therefore, it was concluded that enzymic analysis is useful for diagnosis of affected cats, but is not acceptable for genotyping of carriers.

Immunohistochemical features of proliferative marker and basement membrane components of two feline inductive odontogenic tumours.

Feline inductive odontogenic tumour (FIOT) is a rare and interesting odontogenic neoplasm in which the odontogenic epithelium has inductive potential to form aggregated foci of dental pulp-like mesenchymal cells. Two male cats aged 11 and 10 months presented with nasal swelling and a left maxillary mass. Histopathologically, the masses consisted of non-encapsulated invasive neoplasms exhibiting proliferation of epithelial and mesenchymal components with local infiltration into the maxillary bone in both cases. The epithelial component formed islands, anastomosing strands, and solid sheets of polygonal epithelial cells. Occasionally, these cells formed circular aggregates, resembling the cap stage of odontogenesis. Type IV collagen and laminin were constantly positive around the foci of epithelial cells, and Ki-67 positive indices were extremely low; therefore, these findings consistent with the benign clinical presentation of FIOT.