Other names: Lion Jaw
Affected genes: SLC37A2
Inheritance: Autosomal dominant, incomplete penetrance
Mutation: CanFam3.1 5g.9387327G>A c.1332C>T XM_005619600.3:c.1332C>T (Letko et al., 2020)
OMIA link: 002244-9615

Appropriate breeds for testing: Cairn Terrier, Scottish Terrier, West Highland White Terrier

Symptoms:
Craniomandibular Osteopathy (CMO), also known as "Lion Jaw", is characterized by excessive bone growth in the lower jaw, which eventually recedes. Although the disease may eventually regress or disappear completely, it can sometimes be very painful. Signs of CMO are usually noticed around four to seven months of age. Signs include difficulty or pain in opening the mouth, difficulty in eating or chewing, often associated with loss of appetite, fever, bulging eyes due to swelling of the skull and jaw and excessive salivation.
Hytonen et al. (2016) reported that "determination of the exact mode of inheritance of the disease (in West Highland White Terriers, Cairn Terriers and Scottish Terriers) is not straightforward due to a leaky splice variant contributing to the phenotypic variation. Dogs homozygous for the mutation had no clinical signs as well as heterozygous dogs that had developed CMO suggesting dominant disease with incomplete penetrance which may help explain the reported difference in severity and duration of CMO in affected dogs, although alternative models of transmission cannot yet be completely ruled out.

References:
Letko, A., Leuthard, F., Jagannathan, V., Corlazzoli, D., Matiasek, K., Schweizer, D., Hytönen, M.K., Lohi, H., Leeb, T., Drögemüller, C. Whole genome sequencing indicates heterogeneity of hyperostotic disorders in dogs. Genes (Basel) 11:163, 2020. Pubmed reference: 32033218. DOI: 10.3390/genes11020163.
Hytönen, M.K., Arumilli, M., Lappalainen, A.K., Owczarek-Lipska, M., Jagannathan, V., Hundi, S., Salmela, E., Venta, P., Sarkiala, E., Jokinen, T., Gorgas, D., Kere, J., Nieminen, P., Drögemüller, C., Lohi, H. Molecular characterization of three canine models of human rare bone diseases: Caffey, van den Ende-Gupta, and Raine syndromes. PLoS Genet 12:e1006037, 2016. Pubmed reference: 27187611. DOI: 10.1371/journal.pgen.1006037.