Polymyositis in the Nederlandse Kooikerhondje
By Yvet Opmeer, (DVM and PhD student), and Paul Mandigers
One of the many ongoing research projects in the neurology group focuses on the Kooikerhondje. The Nederlandse Kooikerhondje is traditionally a working dog for the duck hunt. When the endenkoois started to disappear at the beginning of the 20thcentury, the breed was endangered to go extinct. After the second world war, a lot was done to safe the breed. A small genetic foundation of 40 ancestors was formed. Since then, the population has grown a lot. In the meantime, more than 28.000 Kooikerhondjes were bred of whom currently about 7000 are alive.
Today, the Kooikerhondje is an internationally recognized breed with registrations in Europe, Japan and the United States of America. The Kooikerhondje has, like other breeds, many health issues. For two breed specific diseases, the responsible mutation was found (von Willebrand disease/vWD and the hereditary necrotizing myelopathy/ENM). We are currently working at full speed to research and better understand polymyositis since this illness is limiting the breed quite a bit.
The most distinguishing symptoms of this illness are movement and swallowing problems. Dogs with movement problems suffer from a muscle weakness and have a staggered gait. Kooikers with eating problems often drool and have issues swallowing. A combination of both presentations is possible. The diagnosis is made by a combination of symptoms, blood tests, electromyography (EMG) and a muscle biopsy. Usually, the CK (creatinine kinase level) is elevated.
A muscle biopsy is necessary for the diagnosis. Additional functional tests can help in finding the best options for management, prognosis and phenotyping. We find two forms of polymyositis in the Kooiker: a granulomatous myositis and a more lympho-histiocytic myositis.
The biggest focus of our research is, of course, the identification of the underlying genotype (the mutation). With help of a genome-wide association study (GWAS) and the complete genome sequencing (WGS), we have found a mutation. HOWEVER, not all homozygous (having two identical alleles of the particular gene) Kooiker get sick, and on the contrary, some heterozygous (having two different alleles of the particular gene) animals get sick as well. We hope that we can improve the phenotyping with a better pathological description and immunotyping in order to understand which Kooikers get sick and which don’t. The goal is, of course, to eliminate the disease in the population.
Our team consists of Dr. Peter Leegwater, Dr. Hille Fieten (genetics), Prof. Femke Broere (immunology), Prof. Kaspar Matiasek (neuro pathology), Dr. Paul Mandigers (neurology and project manager), Yvet Opmeer (DVM and PhD student) as well as breeder and breed clubs. As you can see, the research is in full speed. If you find in your practice a Kooikerhondje with these clinical symptoms or if you are treating a Kooikerhondje with the diagnosis of Myositis/Polymyositis, please do not hesitate and contact us:
Translation of the German translation (by Claudia Jurasek) by Susanne Martin, MD