We report a male infant with adenylosuccinase deficiency who developed epileptic seizures on the second day of life. Growth was normal and seizures were well controlled with anti-epileptic drugs. Despite axial hypotonia associated with peripheral hypertonicity he presented some development until seven months of age, when he developed high fever and died within a few hours. Although clinical heterogeneity in this disorder of purine synthesis and interconversion is well-known, in 14 out of 17 cases who experienced epilepsy seizures started after the first year of life. The early presentation in our index patient followed by his sudden death at the age of 7 months has not been described before. A search for disorders of purine metabolism should be included in the screening programme for every child with severe neonatal convulsions.