Fil: Priolo, Manuela. Grande Ospedale Metropolitano Bianchi-Melacrino-Morelli. Unità Operativa di Genetica Medica; Italia.Fil: Schanze, Denny. University Hospital Magdeburg. Institute of Human Genetics; Alemania.Fil: Tatton-Brown, Katrin. St. George's University Hospitals NHS Foundation Trust. London and South West Thames Regional Genetics Service. Institute of Cancer Research. Division of Genetics and Epidemiology; Reino Unido.Fil: Mulder, Paul A. Lentis Psychiatric Institute. Jonx Department of Youth Mental Health. Autism Team Northern-Netherlands; Países Bajos.Fil: Tenorio, Jair. Institute of Medical and Molecular Genetics; España.Fil: Kooblall, Kreepa. University of Oxford. Radcliffe Department of Medicine. Academic Endocrine Unit; Reino Unido.Fil: Hernández Acero, Inés. Hospital Universitario Central de Asturias. Genetics Unit; España.Fil: Alkuraya, Fowzan S. King Faisal Specialist Hospital and Research Center. King Abdulaziz City for Science and Technology. Saudi Human Genome Project. Department of Genetics; Arabia Saudita.Fil: Arias, Pedro. Institute of Medical and Molecular Genetics; España.Fil: Bernardini, Laura. Casa Sollievo della Sofferenza Foundation. Cytogenetics Unit; Italia.Fil: Bijlsma, Emilia K. Leiden University Medical Centre. Department of Clinical Genetics; Países Bajos.Fil: Cole, Trevor. Birmingham Women's and Children's NHS Foundation Trust. Department of Clinical Genetics; Reino Unido.Fil: Coubes, Christine. Hôpital Arnaud de Villeneuve. Hospital Center University De Montpellier. Département de Génétique Médicale; Francia.Fil: Dapia, Irene. Institute of Medical and Molecular Genetics; España.Fil: Davies, Sally. University Hospital of Wales. Institute of Medical Genetics; Reino Unido.Fil: Di Donato, Nataliya. Technical University Dresden. Institute for Clinical Genetics; Alemania.Fil: Elcioglu, Nursel H. Marmara University Medical School. Department of Pediatric Genetics; Turquía.Fil: Fahrner, Jill A. Johns Hopkins University School of Medicine. McKusick-Nathans Institute of Genetic Medicine. Department of Pediatrics; Estados Unidos.Fil: Foster, Alison. University of Birmingham. College of Medical and Dental Sciences. Institute of Cancer and Genomic Sciences; Reino Unido.Fil: García González, Noelia. Unit Hospital Universitario Central de Asturias; España.Fil: Huber, Ilka. Sørland Hospital; Noruega.Fil: Iascone, Maria. Azienda Socio Sanitaria Territoriale Papa Giovanni XXIII. Laboratorio di Genetica Medica; Italia.Fil: Kaiser, Ann-Sophie. Heidelberg University. Institute of Human Genetics; Alemania.Fil: Kamath, Arveen. University Hospital of Wales. Institute of Medical Genetics; Reino Unido.Fil: Liebelt, Jan. SA Pathology. South Australian Clinical Genetics Services; Australia.Fil: Lynch, Sally Ann. University College Dublin. School of Medicine and Medical Sciences. Academic Centre on Rare Diseases; Irlanda.Fil: Maas, Saskia M. Academic Medical Center. Department of Clinical Genetics; Países Bajos.Fil: Mammì, Corrado. Grande Ospedale Metropolitano Bianchi-Melacrino-Morelli. Unità Operativa di Genetica Medica; Italia.Fil: Mathijssen, Inge B. Academic Medical Center. Department of Clinical Genetics; Países Bajos.Fil: McKee, Shane. Belfast Health and Social Care Trust. Northern Ireland Regional Genetics Service; Irlanda del Norte.Fil: Menke, Leonie A. University of Amsterdam. Academic Medical Center. Department of Pediatrics; Países Bajos.Fil: Mirzaa, Ghayda M. Seattle Children's Research Institute. Center for Integrative Brain Research; Estados Unidos.Fil: Montgomery, Tara. Newcastle upon Tyne National Health Service Foundation Trust; Reino Unido.Fil: Neubauer, Dorothee. University Hospital Magdeburg. Institute of Human Genetics; Alemania.Fil: Neumann, Thomas E. Mitteldeutscher Praxisverbund Humangenetik; Alemania.Fil: Pintomalli, Letizia. Grande Ospedale Metropolitano Bianchi-Melacrino-Morelli. Unità Operativa di Genetica Medica; Italia.Fil: Pisanti, Maria Antonietta. Antonio Cardarelli Hospital. Medical Genetic and Laboratory Unit; Italia.Fil: Plomp, Astrid S. Academic Medical Center. Department of Clinical Genetics; Países Bajos.Fil: Price, Sue. Northampton General Hospital National Health Service Trust. Department of Clinical Genetics; Reino Unido.Fil: Salter, Claire. Princess Ann Hospital. Wessex Clinical Genetics Service; Reino Unido.Fil: Santos-Simarro, Fernando. Institute of Medical and Molecular Genetics; España.Fil: Sarda, Pierre. Hôpital Arnaud de Villeneuve. Hospital Center University De Montpellier. Département de Génétique Médicale; Francia.Fil: Segovia, Mabel. ANLIS Dr.C.G.Malbrán. Centro Nacional de Genética Médica; Argentina.Fil: Shaw-Smith, Charles. Royal Devon and Exeter National Health Service Foundation Trust; Reino Unido.Fil: Smithson, Sarah. University Hospitals Bristol National Health Service Trust; Reino Unido.Fil: Suri, Mohnish. Nottingham University Hospitals National Health Service Trust. Nottingham Clinical Genetics Service; Reino Unido.Fil: Valdez, Rita Maria. Hospital Militar Central Cirujano Mayor Dr. Cosme Argerich. Genetics Unit; Argentina.Fil: Van Haeringen, Arie. Leiden University Medical Centre. Department of Clinical Genetics; Países Bajos.Fil: Van Hagen, Johanna M. Vrije Universiteit Medical Centre. Department of Clinical Genetics; Países Bajos.Fil: Zollino, Marcela. Catholic University. Institute of Medical Genetics. Department of Laboratory Medicine; Italia.Fil: Lapunzina, Pablo. Institute of Medical and Molecular Genetics; España.Fil: Thakker, Rajesh V. University of Oxford. Radcliffe Department of Medicine. Academic Endocrine Unit; Reino Unido.Fil: Zenker, Martin. University Hospital Magdeburg. Institute of Human Genetics; Alemania.Fil: Hennekam, Raoul C. University of Amsterdam. Academic Medical Center. Department of Pediatrics; Países Bajos.Malan syndrome is an overgrowth disorder described in a limited number of individuals. We aim to delineate the entity by studying a large group of affected individuals. We gathered data on 45 affected individuals with a molecularly confirmed diagnosis through an international collaboration and compared data to the 35 previously reported individuals. Results indicate that height is > 2 SDS in infancy and childhood but in only half of affected adults. Cardinal facial characteristics include long, triangular face, macrocephaly, prominent forehead, everted lower lip, and prominent chin. Intellectual disability is universally present, behaviorally anxiety is characteristic. Malan syndrome is caused by deletions or point mutations of NFIX clustered mostly in exon 2. There is no genotype-phenotype correlation except for an increased risk for epilepsy with 19p13.2 microdeletions. Variants arose de novo, except in one family in which mother was mosaic. Variants causing Malan and Marshall-Smith syndrome can be discerned by differences in the site of stop codon formation. We conclude that Malan syndrome has a well recognizable phenotype that usually can be discerned easily from Marshall-Smith syndrome but rarely there is some overlap. Differentiation from Sotos and Weaver syndrome can be made by clinical evaluation only.