ARG1 and Spastic tetraplegia: ARG1 deficiency often manifest during preschool age with progressive loss of psychomotor functions, spastic tetraplegia, seizures, growth retardation, severe hepatic diseases, and hepatocellular carcinoma.4, 5, 6, 7 The incidence (birth prevalence) of ARG1 deficiency continues to be a subject of growing interest.8