GM3 Synthase Deficiency

Background and History: 

This condition was described in 2004 as a disorder resulting from an inherited enzyme deficiency.  As a result patients are unable to metabolize a dietary ingredient necessary for the synthesis of essential components of cells, especially those of the brain.

Clinical Correlations: 

Infants usually appear normal for the first weeks of life but soon develop signs of developmental stagnation.  Seizures (epilepsy) are also evident in the first months of life.  Many babies are ‘floppy’ and lack muscle tone.  They never achieve the usual childhood developmental milestones such as sitting, head holding, walking, and talking.  They do not respond to lights or other visual stimuli in their environment and the optic nerves are damaged.  In fact, these children are generally unresponsive to any environmental stimuli.  They display irritability, failure to thrive, vomiting, and poor feeding.  Virtually all children require gastric tube feeding for nutrition.


This is an autosomal recessive disorder that requires mutations in both copies of a gene.  Parents who are carriers have no symptoms but can expect that each of their children will have a 1 in 4 chance of developing GM3 synthase deficiency.

Diagnosis and Prognosis: 

A pediatrician can suspect the diagnosis and a neurologist usually is the one to confirm it.  Treatment is supportive as there is none for the enzyme deficiency.  Anti-epileptic medications are often prescribed but are usually of little benefit in treating the epilepsy.  Lifespan is unknown but at least some patients have lived until late in the 2nd decade of life.

Additional Information
Autosomal recessive