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American Maltese Association

A National Breed and Member club of the American Kennel Club

Glycogen Storage Disease (GSD)

Written by: 
Vicki Fierheller

GSD is an inherited metabolic disorder involving the conversion of glucose (the body's sugar energy) to or from the storage form, which is glycogen. Various enzymes (catalysts) are required to activate the change from one state to the other. Any deficiency or absence of one of the enzymes results in GSD.

GSD is seen in humans as well as dogs. In people, it can be treated, but never cured and long-term complications are common. GSD in Maltese was discovered incidentally when a Georgia Maltese breeder lost two 6-week-old puppies. When the puppies were necropsied, it was discovered that their livers and kidneys showed increased levels of glycogen. The pathologist contacted Duke University and brought the attention of these puppies to Dr. Y.T. Chen,  a world expert for the various forms of GSD in humans.

Of the roughly 11 known types of GSD, it was discovered that these puppies had GSD Type Ia. This is the absence or lack of the enzyme glucose-6-phosphatase, which is involved in the final step in the production of glucose by the liver. 'The affected puppies showed a general failure to thrive, hypoglycemia (low blood sugar), mental depression, poor body condition and failure to nurse (symptoms of fading puppy syndrome)'.

Other signs may include puppies that do nurse, but with very poor growth, i.e., possibly never gaining much beyond birth weight; and puppies that seem thin and yet have distended bellies due to enlarged livers.

Blood taken from affected puppies would show that the glucose level is very low and cholesterol is very high.  Sadly, affected puppies will not survive.

As a side note, some Maltese puppies can have juvenile hypoglycemia, which should not be confused with GSD.  GSD puppies will have a general overall sickly appearance, while puppies with hypoglycemia will look and act healthy.  GSD puppies will have chronic low glucose levels, while hypoglycemic puppies will have normal glucose levels except when they have a hypoglycemic attack.

As hard as it may be for a breeder, any puppy that does not survive should be necropsied to try to determine the cause.

Fortunately, there is a genetic test available for GSD-Ia through Paw Print Genetics.  The test simply requires a cheek swab for DNA analysis.  Because GSD is an autosomal recessive disorder, the test will determine if a dog is clear (does not have the mutation gene) or a carrier (carries the mutation gene, but does not have GSD).  For more information about the test, visit

GSD is assumed to be a very rare disorder in Maltese.  However, it is still a good idea to test breeding pairs, particularly if there is unusual puppy loss occurring.  Carriers need not be removed from a breeding program as long as they are only bred to a clear partner.

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