Monogenic dilated cardiomyopathy described in the Standard Schnauzer and the Giant Schnauzer, associated with a homozygous 22 bp deletion in the RBM20 gene (splicing regulator). It produces dilation and systolic dysfunction of the left ventricle, with congestive heart failure and premature death in homozygotes.

In Standard Schnauzers, ~21% carried at least one allele (19.7% heterozygotes; 1.5% homozygotes); in Giant Schnauzers, 9.8% (Leach et al. 2022). The variant was not detected in the other breeds analysed.

- Left ventricular dilation\n- Reduced ejection fraction\n- Ventricular arrhythmias\n- Exercise intolerance and lethargy\n- Congestive heart failure\n- Premature death in homozygotes

Leach et al. (2014, conference communication) described in the Standard Schnauzer a familial DCM associated with a homozygous 22 bp deletion in RBM20. Harmon et al. (2017) characterised the clinical picture in 15 cases and Leach et al. (2022) confirmed the association of the homozygous genotype with DCM and shorter life expectancy in Standard and Giant Schnauzers.

- Test Standard and Giant Schnauzer breeding dogs before mating\n- Autosomal recessive inheritance: do not use homozygotes as breeding dogs\n- Do not mate two carriers (25% homozygotes per litter)\n- A carrier can be mated to a clear dog; test the offspring intended for breeding\n- Cardiac assessment (echocardiography and Holter) of homozygotes\n- Record the status in the pedigree

Differential diagnosis with other DCMs (idiopathic, nutritional, taurine deficiency) and with arrhythmogenic cardiomyopathy. The RBM20 variant does not explain all cases of DCM in the breed. The primary causal source (Leach et al. 2014) is a conference presentation without a complete peer-reviewed publication; caution is advised.

Leach SB et al. 2014. Dilated cardiomyopathy in standard schnauzers with a homozygous 22 bp deletion in RBM20. Proceedings of the 32nd ACVIM Forum (ponencia, sin PMID); Harmon MW et al. 2017. Dilated Cardiomyopathy in Standard Schnauzers: Retrospective Study of 15 Cases. J Am Anim Hosp Assoc. PMID: 27841675; Leach SB et al. 2022. Prevalence, geographic distribution, and impact on lifespan of a dilated cardiomyopathy-associated RNA-binding motif protein 20 variant in genotyped dogs. J Vet Cardiol. PMID: 34144877