Polymyositis (and HNM) in “Het Nederlandse Kooikerhondje”
Summary of a lecture given by Dr Paul Mandigers during a symposium of the VHNK
Dr. Paul Mandigers discussed the relevance of HMN ( hereditary necrotizing myelopathy) and polymyositis (PMN) to breed health. His colleagues of ECGC (Expertise Centre Genetics Companion Animals) conceptualize development of a breeding app. This app would utilize various resources such as pedigree, molecular markers, health data, show results etc to support estimated breeding values.
Contrasting the differences in research cost and details between HMN and PMN, funding is needed to continue the more elusive search for PMN carrier testing.
Clinically dogs with PMN may present with problems swallowing ( eating, drinking, salivation) and/ or locomotion. Presentation is varied from mild to severe with progression ranging from resolution to reoccurrence to demise. Relying on reported data from the Dutch club registration, approximately 2% of dogs are affected with a carrier rate of 20-30%. Roughly 17% present under 1 year of age; 25% between 1-2 years or age; 11% between 2-3 years of age; 11% between 3-4 years of age and 36% are greater than 4 years of age at time of presentation.
In muscle biopsies (the current goldstandard to diagnose), variants of lymphocytic polymyositis, eosinophilic (lymphocytic) polymyositis and granulomatous histiocytic polymyositis and various combinations exist with mild to severe symptoms. Recognition of mild cases can be difficult with elevation of CK (creatine kinase) suggestive but not diagnostic of disease. Due to differing presenting phenotype so, treatment has ranged from supplements to corticosteroids to spontaneous resolution with varying responses.
No genetic test has been developed yet.
Research has identified a region with 4 important genes. Use of genetic sequencing has shown 2 of the genes to be abnormally up-regulated in PMN. However, it is complex, as heterozygous dogs can get sick while a few homozygous dogs remain healthy. Ideally, research would allow for identification of either phenotypic mutations or variance by expanding the genetic sequencing or affected homozygous dogs, heterozygous dogs and controls.
The anticipated cost is 10,000 to 20,000 Euros with already 50,000 Euros expended. Continued funding and support is needed to solve this complex genetic issue.
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