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Canine Mendelian disease record

Muscular Hypertrophy (Double Muscling)

Muscular Hypertrophy (Double Muscling). Autosomal recessive. Observed in 1 of 266 breeds tested in the Sniff Atlas, with measured carrier frequencies drawn from 242,664 dogs (Donner 2023). Per-dog phenotype outcome depends on penetrance, modifiers, and environment; the carrier frequencies below describe variant prevalence, not disease incidence.

OMIA identifier
OMIA:000683-9615
Autosomal recessive
Source dataset
Sniff Atlas v1.0.1 / DOI
The human connection

A model of human myostatin-related muscle hypertrophy

Dogs with this condition carry a change in DyakGE28501. In people, changes in the same gene cause myostatin-related muscle hypertrophy. That makes affected dogs a naturally-occurring model of the human disease, and it is part of why studying dogs moves medicine forward for everyone. It does not mean your dog has the human disease. It means the two share an underlying biology.

In people, the disease is described as: Myostatin-related muscle hypertrophy is a rare condition characterized by reduced body fat and increased muscle size. Affected individuals have up to twice the usual amount of muscle mass in their bodies. They also tend to have increased muscle strength. This condition is not known to cause any medical problems, and affected individuals are intellectually normal. Myostatin-related muscle hypertrophy is caused by mutations in the MSTN gene. It follows an incomplete autosomal dominant pattern of inheritance.

In humans it is also called: MSLHP, muscle hypertrophy.

MONDO:0013598 OMIM 614160

Mapped from OMIA via the human disease's OMIM entry to the Mondo Disease Ontology (Monarch Initiative, CC-BY 4.0). Sniff renders this as a model-of link; the canine disease remains the subject of this page.

About this disease

From OMIA's curated record

Documented in OMIA (Online Mendelian Inheritance in Animals). This describes the disease as recorded in the published literature, not a prediction for any individual dog. As of 2026-06-03.

Summary

In addition to the occurrence of natural variants for this trait, variants have been created artificially (e.g. Zou et al., 2015): Genetically-modifed organism; GMO.

Clinical features

Affected dogs show an unusual amount of muscularity, especially in the neck and legs. They are broad chested and typically don’t conform to the breed standard (slim, long neck, pointed snout) (Mosher et al., 2007). Dogs with a single copy of the mutation show a smaller degree of hypermuscularity are significantly faster than homozygous wild-type whippets (Mosher et al., 2007). Hence, being heterozygous for the mutation is considered performance enhancing. For whippets with a double copy of the mutation, there is little evidence about potential associated health risks. It has been anecdotally reported amongst breeders that affected whippets are otherwise generally healthy and only suffer from occasional muscle cramps and a distinctive overbite (Mosher et al., 2007). IT thanks DVM student Lucas Anderson, who provided the basis of this contribution in May 2023.

Human analog

OMIA links this condition to its human counterpart in OMIM (Mendelian Inheritance in Man), the place to read across to the deeper human literature for the same biology.

Disease · OMIM 614160 Gene · OMIM 601788

Source: OMIA (Nicholas, Tammen & the Sydney Informatics Hub), entry OMIA:000683-9615, doi:10.25910/2AMR-PV70 (CC-BY 4.0).

Signs & cross-references

How it presents

Catalogued in the Mondo disease ontology (the cross-species disease identity used by the Monarch Initiative) as myostatin-related muscle hypertrophy (MONDO:0013598).

Phenotype terms: Human Phenotype Ontology + Mammalian Phenotype Ontology; disease terms: Mondo (Monarch Initiative). Cross-references curated by OMIA (doi:10.25910/2AMR-PV70, CC-BY 4.0).

The evidence

Published references

The peer-reviewed papers behind this disease, curated by OMIA. Starred entries are OMIA-designated landmark papers. Showing 6 of 8.

  4. Generation of gene-target dogs using CRISPR/Cas9 system. · J Mol Cell Biol · 2015 · PMID 26459633

References curated by OMIA (Nicholas, Tammen & the Sydney Informatics Hub), doi:10.25910/2AMR-PV70 (CC-BY 4.0). Full list at the OMIA entry.

Predict a litter

Set each parent's status for Muscular Hypertrophy (Double Muscling) and see the odds for their puppies. Single recessive variant, exact Mendelian math.

Parent A
Parent B
NNClear
NmCarrier
NmCarrier
mmAffected
Clear25%
Carrier50%
Affected25%

These are the genetic odds for one known variant, not a promise: a real litter varies around them, and penetrance or other genes can change whether the condition ever appears. Use it to avoid pairing two carriers and to keep a line healthy, not to engineer a dog. Inheritance mode per OMIA.
Your breed

See what Muscular Hypertrophy (Double Muscling) looks like in your dog's breed.
Carrier frequency by breed

Top 1 well-sampled breeds (n ≥ 50)

Maximum per breed across variants in the Donner 2023 cohort, with . The list below is split into well-sampled breeds (n ≥ 50 tested) and small-sample breeds (n < 50, where the Wilson CI typically spans more than 20 percentage points and frequencies should not be compared directly to the well-sampled entries). Frequencies are population-level, not per-litter or per-line.

0%3%5%
Greyhound0.48% · n 105
n = 105 dogs · Donner et al. 2023 carrier-screening cohort · Sniff Atlas
Each bar is one well-sampled breed; the whisker is its Wilson 95% CI, and fainter bars have wider intervals. Frequencies are population-level, not per-litter. Carrier status for Muscular Hypertrophy (Double Muscling) is measured; phenotype outcome depends on penetrance and modifiers.
▸ Full table with Wilson 95% confidence intervals
Breed Carrier frequency n tested
Greyhound 0.48% 105

265 additional breeds in the Donner 2023 cohort were tested but showed no carriers.

Scope of this record

Scope

This record carries the breed-level carrier frequencies from the Donner 2023 cohort. Penetrance data (the fraction of at-risk dogs that develop the phenotype) is not yet quantified for this disease in the Sniff Atlas v1.0.1. The OMIA entry is the authoritative reference for the clinical phenotype, inheritance pattern, and gene assignment.

Predicted disease relevance at the per-dog level is UNPROVEN. The carrier frequency is measured; phenotype outcome depends on penetrance, environment, and modifier loci. Consult a veterinarian for clinical interpretation.

How to cite this record

Citations

If you use this record in published work, cite the Sniff Atlas (the published dataset that carries the breed-level carrier frequencies) and the upstream sources:

  • Sniff Atlas v1.0.1 for the per-breed carrier frequencies:

    Gehring, M. (2026). Sniff Atlas v1.0.1. Zenodo. https://doi.org/10.5281/zenodo.20566358. CC-BY 4.0.

  • OMIA for the disease definition, inheritance, and gene assignment:

    Nicholas, F. W., & Tammen, I. (2024). OMIA. Sydney Informatics Hub, The University of Sydney. https://doi.org/10.25910/2AMR-PV70. Entry: OMIA:000683-9615.

  • Donner et al. 2023 for the breed × variant carrier-frequency cohort:

    Donner, J., Freyer, J., Davison, S., Anderson, H., Blades, M., Honkanen, L., et al. (2023). Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs. PLOS Genetics, 19(2), e1010651. https://doi.org/10.1371/journal.pgen.1010651.

Full citation formats (BibTeX, RIS, CITATION.cff) at sniff.world/cite.

Related

Related

Last updated
Sources: Sniff Atlas v1.0.1 · OMIA OMIA:000683-9615 · Donner et al. 2023