GM-1 and GM-2 Gangliosidosis in Cats

Gangliosidosis is a hereditary disorder that is also known as lysosomal storage disease. Cats with the disorder don't have an essential enzyme that they need to metabolise specific fats known as lipids and as such, these fats build up in cells that make up a cat's body which in turn means they cannot function as they should causing all the problems. Any cat known to suffer from gangliosidosis should never be used in a breeding programme and should be spayed or neutered when the time is right for them to undergo the procedures.

The Two Forms of Gangliosidosis in Cats

There are two forms of the disorder which are as follows:

• GM1 - this form of the disorder is caused by a lack of a specific enzyme known as acid β galactosidase
• GM2 - this form of the disoder is caused by a lack of enzymes known as hexosaminidase A and B

As previously mentioned, the disorder results in an accumulation of fats which are known as gangliosides in a cat's neuronal cells which are found in their central nervous system.

Symptoms to Watch Out For

When a cat inherits the disorder, they develop neurological symptoms of there being something wrong which as time passes get progressively worse. Typical symptoms of a cat suffering from the condition could include the following:

• Ataxia - a condition that affects a cat's movement which becomes more uncoordinated
• Dysmetria - a condition that sees cats develop a high-stepping gait
• Tremours
• Nystagmus - this is a condition where cats develop a strang eye movement that goes side to side

Diagnosing the Condition

A vet would need to know a cat's full medical history and ideally their ancestry too which would help when establishing a correct diagnosis. They would thoroughly examine a cat and would carry out several tests to confirm the following:

• Whether a cat's white blood cells contain cytoplasmic granules
• Whether a cat's liver is enlarged
• Whether a cat has a small skull and flat broad head
• Whether there is any clouding of a cat's cornea which has impaired their vision
• Whether a kitten’s growth is stunted

The signs of there being something wrong typically manifest themselves when kittens are anything from one to five months old and their symptoms get progressively worse as time passes. Cats show weakness in their back legs followed by weakness in their front ones. Other signs to watch out for include the following:

• Depression
• Seizures

Sadly, kittens with the condition usually succumb to the disorder when they anything between 8 to 10 months old.

The Causes

It has been established that the cause of gangliosidosis GM1 is a defect in a cat's GLB1 gene. However, with GM2, the cause is in a defect in a cat's HEXB gene and that it is a hereditary disorder that affects certain breeds more than others.

Testing for Gangliosidosis

Both types of gangliosidosis are known to be caused by a simple autosomal recessive gene with affected cats being known as being homozygous which in short means they have two copies of the damaging gene. Cats that only have one copy of the gene are referred to as being asymptomatic carriers. Thankfully, there are DNA tests for both carriers and cats that have both types of gangliosidosis. All cats known to be carriers or to be affected by the condition should never be used in a breeding programme and all cats more predisposed to suffering from the condition should be screened.

Breeds Most at Risk

The breeds known to be predisposed to suffering from GM1 gangliosidosis are as follows:

• Korat
• Siamese
• Serengeti
• Thai
• Domestic cats (mixed breeds)

The breeds known to be predisposed to suffering from GM2 gangliosidosis include the following:

• Korat
• Burmese
• Domestic cats (mixed breeds)

Dealing with Carriers

Both females and males can be carriers"" of the condition if they only inherit one copy of the defective gene. As such, a cat would not develop the condition themselves, but if bred, they would pass the disorder on to their offspring. As such, all cats known to be predisposed to inheriting the disorder whether they are ""affected"" or ""carriers"" should never be used in a breeding programme as this is the only way of ensuring the condition is not pass on to their offspring. Cats should therefore be spayed or neutered when the time is right for them to undergo the procedures to prevent them from mating.

Responsible Breeding is Essential

All responsible breeders routinely have their stud cats screened for gangliosidosis and would never use a cat known to have inherited the condition in a breeding programme which is why responsible breeding is so essential in breeds known to suffer from GM1 and GM2 gangliosidosis.

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