Lavender foal syndrome

Overview

Lavender foal syndrome (LFS), also known as coat color dilution lethal (CCDL), is a fatal genetic disorder seen in Arabian horses, particularly those of Egyptian lineage. It is named for the distinctive diluted, silvery or lavender-gray coat color observed in affected foals. LFS is a neurological condition characterized by severe central nervous system dysfunction that becomes evident at birth. Affected foals are typically unable to stand or nurse and often exhibit abnormal movements or seizures. Due to the severity of the symptoms, LFS is invariably fatal shortly after birth.

Causes

Lavender foal syndrome is caused by a mutation in the MYO5A gene, which plays a critical role in intracellular transport and neurological function. The condition follows an autosomal recessive inheritance pattern, meaning a foal must inherit two copies of the mutated gene—one from each parent—to be affected. Horses that carry only one copy of the gene are known as carriers and do not show any symptoms but can pass the mutation to their offspring.

Symptoms

Clinical signs of LFS are apparent at birth and are neurological in origin. Common symptoms include:

• Unusual coat color – diluted or lavender-gray coat, often metallic or silvery in appearance

• Inability to stand or nurse – foals are typically weak, recumbent, and non-ambulatory

• Seizures – including paddling, muscle rigidity, or opisthotonos (arching of the back and neck)

• Abnormal eye movements – such as nystagmus (rapid involuntary eye movement)

• Hyperextension or stiffness of limbs

• Lack of coordination and reflexes

The combination of neurological deficits and inability to perform basic survival functions leads to rapid deterioration.

Diagnosis

Diagnosis of Lavender foal syndrome is primarily based on clinical presentation and genetic testing. Diagnostic steps include:

• Clinical observation – recognizing hallmark symptoms in a newborn foal, particularly if both parents are of Egyptian Arabian descent

• Genetic testing – a definitive diagnosis can be made via DNA testing to detect the MYO5A gene mutation

• Carrier screening – recommended for breeding stock to prevent transmission of the defective gene

• Necropsy (post-mortem) – may confirm neurological abnormalities if the foal has died

Treatment

There is no effective treatment or cure for Lavender foal syndrome. Due to the severity and irreversibility of the neurological impairments, supportive care is typically not successful. Management steps include:

• Humane euthanasia – recommended shortly after birth to prevent prolonged suffering

• Genetic counseling – to educate breeders about carrier status and inheritance patterns

• Breeding management – avoid mating two carriers to prevent producing affected foals

Prognosis

The prognosis for foals born with Lavender foal syndrome is uniformly poor. All known cases result in death within a few hours or days of birth, despite any supportive measures. However, through widespread use of genetic testing, carriers can be identified, and breeding programs can be adjusted to prevent future cases. With responsible breeding and awareness, LFS is a preventable condition in the Arabian horse population.