Germline heterozygous pathogenic variations of the nuclear receptor-binding SET domain-containing protein 1 (NSD1, also known as KMT3B), notably the gene truncation and missense mutations, are detected in more than 90% of patients with Sotos syndrome and thus nominated as the main causal lesion of this disease (4, 5, 6, 7). This evidence concerns the gene NSD1 and Sotos syndrome.