Muscles
A muscle condition whose signs can differ widely between horses.
Dominant inheritance
Genetic health · inherited conditions
Inherited diseases in horses
Inherited conditions can affect muscles, skin, immune defenses or a foal’s development. Their effects and inheritance patterns differ. These guides explain each condition and show what a genetic test can help establish.
This collection covers inherited conditions and genetic susceptibility for which DNA testing is available. It will grow over time and does not cover every equine genetic disorder.
What the guides explain about inherited diseases in horses
Symptoms of inherited diseases in horses
Each guide starts with what the condition can change in the body. Similar signs can have different causes: a description helps explain a condition but cannot provide a diagnosis.
How inherited diseases can pass from parents to a foal
For a dominant condition, one copy of a variant may be enough to produce an effect. For the recessive conditions described here, a horse with one copy can pass it on without having that condition. The effects of two copies depend on the condition.
What a DNA test can reveal about an inherited disease
A test covers a particular variant or set of variants. Its result helps explain a situation, but cannot describe a horse’s entire health or always predict the severity of signs.
Find a guide to an inherited disease in horses
Each entry opens a full article about the condition. Search by name or choose the main function affected; some conditions affect more than one part of the body.
Search names, abbreviations and the populations mentioned in the guides. For example: HERDA, Arabian or Connemara.
19 guides shown
- Muscles
Episodes of muscle tremors or weakness that can sometimes be severe.
Dominant inheritance
- Skin and supporting tissues
Fragile skin, with signs that may not become apparent until well after birth.
Recessive inheritance
- Skin and supporting tissues
A very severe condition affecting supporting tissues, also known as WFFS.
Recessive inheritance
- Immune defenses
Severely impaired immune defenses against infection.
Recessive inheritance
- Nervous system
A condition of the cerebellum that can impair balance and coordination.
Recessive inheritance
- Digestion
A specific link between the frame overo variant and a severe intestinal disorder.
Recessive inheritance
- Hooves
Weakness of the outer hoof wall, with variable signs.
Recessive inheritance
- Metabolism
A fatal recessive disorder affecting the energy reserve of a fetus or young foal.
Recessive inheritance
- Muscles
Susceptibility to severe muscle and metabolic episodes, particularly with certain triggering anaesthetic agents.
Dominant inheritance
- Muscles
Susceptibility to muscle wasting or nonexertional muscle injury that does not develop in every positive horse.
Codominant inheritance
- Nervous system
Fatal neurological disease from birth, often accompanied by a diluted coat. Coat color alone cannot establish the diagnosis.
Recessive inheritance
- Immune defenses
Progressive anemia and inadequate immune defenses in a young foal. FIS differs from SCID and requires its own test.
Recessive inheritance
- Skin and supporting tissues
Severe fragility of a newborn foal’s skin and mucous membranes. The tested forms, JEB1 and JEB2, involve different genes and need separate interpretation.
Recessive inheritance
- Eyes and vision
Very limited vision in dim light, present from birth. The form linked to the LP allele in TRPM1 and the CSNB2 form linked to GRM6 each require a different DNA test.
Recessive inheritance
- Eyes and vision
A horse with one copy of the Silver variant in PMEL can have developmental eye abnormalities. These are generally more extensive with two copies of the variant. Silver can remain hidden in a chestnut coat.
- Bones and skeletal development
Disproportionate growth with short limbs and unusually loose joints. This form can allow a good quality of life and should not be confused with every equine dwarfism disorder.
Recessive inheritance
- Nervous system
Abnormal fluid accumulation in the developing brain, investigated particularly in Friesian horses.
Recessive inheritance
- Bones and skeletal development
A disorder of limb bone development that can cause deformity and impaired movement.
Recessive inheritance
Research and scientific resources about inherited diseases in horses
Each article brings together research and resources from universities and laboratories. Visit the condition’s page for its bibliography and the references supporting each explanation.
- Polysaccharide storage myopathy type 1 (PSSM1)
- Hyperkalemic periodic paralysis (HYPP)
- Hereditary equine regional dermal asthenia (HERDA)
- Fragile foal syndrome type 1 (WFFS / FFS)
- Severe combined immunodeficiency (SCID)
- Cerebellar abiotrophy (CA)
- Lethal white overo syndrome (LWO)
- Hoof wall separation disease (HWSD)
- Glycogen branching enzyme deficiency (GBED)
- Malignant hyperthermia (MH)
- MYH1-associated myopathy (MYHM)
- Lavender foal syndrome (LFS)
- Foal immunodeficiency syndrome (FIS)
- Junctional epidermolysis bullosa (JEB)
- Congenital stationary night blindness (CSNB)
- Multiple congenital ocular anomalies (MCOA)
- B4GALT7-associated Friesian dwarfism (B4GALT7)
- Inherited hydrocephalus (B3GALNT2)
- Skeletal atavism (SA)