GM3 synthase deficiency is characterized by recurrent seizures (epilepsy) and problems with brain development. Within the first few weeks after birth, affected infants become irritable and develop feeding difficulties and vomiting that prevent them from growing and gaining weight at the usual rate. Seizures begin within the first year of life and worsen over time. Multiple types of seizures are possible, including generalized tonic-clonic seizures (also known as grand mal seizures), which cause muscle rigidity, convulsions, and loss of consciousness. Some affected children also experience prolonged episodes of seizure activity called nonconvulsive status epilepticus. The seizures associated with GM3 synthase deficiency tend to be resistant (refractory) to treatment with antiseizure medications. The disease is Monarch Disease Ontology id MONDO_0018274 (GM3 synthase deficiency). Also known as: Amish infantile epilepsy syndrome, SPDRS, ST3GAL5-CDG, disorder of lactosylceramide alpha-2,3-sialyltransferase activity, epilepsy syndrome, infantile-onset symptomatic, infantile-onset symptomatic epilepsy syndrome - developmental stagnation - blindness, infantile-onset symptomatic epilepsy syndrome-developmental stagnation-blindness syndrome, lactosylceramide alpha-2,3-sialyltransferase activity disease.