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. 2025 May 30:12:1559040.
doi: 10.3389/fvets.2025.1559040. eCollection 2025.

Age of onset, treatment response, and survival rates in Dutch Kooiker dogs diagnosed with hereditary polymyositis

Yvet Opmeer  1   2 , Vanessa Alf  3 , Peter A J Leegwater  1 , Hille Fieten  1 , Paul J J Mandigers  1   2
Affiliations

Age of onset, treatment response, and survival rates in Dutch Kooiker dogs diagnosed with hereditary polymyositis

Yvet Opmeer et al. Front Vet Sci. .

Abstract

Introduction: Hereditary polymyositis in Kooiker dogs is genetically linked to the deletion of a 39 kb DNA fragment located 10 kb upstream of the interleukin IL21/IL2 locus, exhibiting low penetrance. This study aims to identify prognostic factors for Kooiker dogs that are affected and evaluate three treatments: (1) glucocorticoid monotherapy, (2) glucocorticoids combined with supplements (vitamin B, L-carnitine, and coenzyme Q10), and (3) glucocorticoids combined with supplements and oclacitinib.

Method: This study incorporates both retrospective and prospective designs. A total of 97 Kooiker dogs diagnosed with histopathologically confirmed polymyositis, or those showing clinical signs consistent with polymyositis and homozygous or heterozygous for a 39-kb deletion, were included. Dogs seen before the end of 2006 received only Treatment 1, those identified between 2007 and 2015 received Treatment 2, and those seen after 2015 received Treatment 3. A dataset was created that included sex, neuter status, age of onset (AoO), the 39 kb deletion, clinical signs, treatment, creatinine kinase (CK) activity at diagnosis and during follow-up visits, owner-reported improvement during treatment, cause of death, and date of death. Descriptive statistics and Cox proportional hazards survival analysis were conducted to examine factors influencing age of onset, treatment response, and survival.

Results: The 39 kb deletion showed no association with clinical signs or creatine kinase (CK) activity at diagnosis. However, homozygous Kooiker dogs with the 39 kb deletion had a lower AoO. A significant decrease in CK activity was observed in 18 dogs during the first recheck after treatment, and most owners reported clinical improvement following the start of treatment. The type of treatment influenced survival time, with dogs treated with glucocorticoids, supplements, and oclacitinib having the longest survival.

Discussion: A treatment regimen that included glucocorticoids, supplements, and oclacitinib was the most effective in this study, although it was not statistically significant.

Keywords: L-carnitine; apoquel; coenzyme Q10; myopathy; oclacitinib; prednisolone; treatment; vitamin B.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

Figures

Figure 1
Figure 1
Box plot illustrating AoO for the two genotypes: homozygous (Del/Del) and heterozygous (Del/WT). The difference is statistically significant (p = 0.011).
Figure 2
Figure 2
illustrates the cumulative hazard probability curves for death due to polymyositis across different therapy groups, adjusted for the mean age of onset. TG1 represents glucocorticoids only, TG2 indicates a glucocorticoid combined with supplements, and TG3 includes TG2 plus oclacitinib.
See this image and copyright information in PMC

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