Any hypotonia, infantile, with psychomotor retardation and characteristic facies in which the cause of the disease is a mutation in the NALCN gene. The disease is hypotonia, infantile, with psychomotor retardation and characteristic facies 1 (Monarch Disease Ontology id MONDO_0024567). Also known as: NALCN hypotonia, infantile, with psychomotor retardation and characteristic facies, hypotonia, infantile, with psychomotor retardation and characteristic facies caused by mutation in NALCN.