MED13L syndrome is a developmental disorder characterized by developmental delay, intellectual disability, and minor differences in facial features. Additionally, some people with this condition have recurrent seizures (epilepsy) or heart abnormalities that are present from birth (congenital heart defects).

Intellectual disability and developmental delay are usually moderate to severe in people with MED13L syndrome. Weak muscle tone (hypotonia) and delayed development of motor skills, such as sitting, standing, and walking, are early symptoms of the condition. After learning to walk, some affected individuals continue to have difficulty with coordination and balance (ataxia). Speech is also delayed, and most people with this condition develop only a few words or never learn to talk. People with MED13L syndrome may exhibit characteristics typical of autism spectrum disorder, including repetitive actions and difficulty with social interactions.

Most people with MED13L syndrome have unusual facial features that consist of a depressed nasal bridge, a bulbous nasal tip, straight eyebrows, outside corners of the eyes that point upward (upslanting palpebral fissures), full cheeks, and an open mouth. Other facial features that sometimes occur are a pronounced double curve of the upper lip (Cupid's bow), and a deep space between the nose and upper lip (philtrum).

Different congenital heart defects can occur in MED13L syndrome. Affected individuals may have transposition of the great arteries, which is abnormal positioning of the large blood vessel that distributes blood from the heart to the rest of the body (aorta) and the artery that carries blood from the heart to the lungs (the pulmonary artery). Other congenital heart defects in MED13L syndrome include a hole between the two lower chambers of the heart (ventricular septal defect), a hole between the two upper chambers of the heart (patent foramen ovale), or a particular combination of heart defects known as tetralogy of Fallot.

MED13L syndrome is a rare disorder that occurs in an estimated 1.6 per 100,000 newborns. More than 65 affected individuals have been reported in the scientific literature.

As its name suggests, MED13L syndrome is caused by mutations in a gene known as MED13L. This gene provides instructions for making a protein that helps regulate gene activity; it is thought to play an essential role in development both before and after birth. The MED13L gene mutations that cause this condition alter the function of the MED13L protein or reduce the amount of protein present, impairing normal control of gene activity. It is unclear how these changes lead to the particular developmental and physical features of MED13L syndrome.

Genetic Testing Information

• Genetic Testing Registry: Cardiac anomalies - developmental delay - facial dysmorphism syndrome

Genetic and Rare Diseases Information Center

• Developmental delay-facial dysmorphism syndrome due to MED13L deficiency

Patient Support and Advocacy Resources

• National Organization for Rare Disorders (NORD)

Catalog of Genes and Diseases from OMIM

• IMPAIRED INTELLECTUAL DEVELOPMENT AND DISTINCTIVE FACIAL FEATURES WITH OR WITHOUT CARDIAC DEFECTS; MRFACD

Scientific Articles on PubMed

• PubMed

• Asadollahi R, Oneda B, Sheth F, Azzarello-Burri S, Baldinger R, Joset P, Latal B, Knirsch W, Desai S, Baumer A, Houge G, Andrieux J, Rauch A. Dosage changes of MED13L further delineate its role in congenital heart defects and intellectual disability. Eur J Hum Genet. 2013 Oct;21(10):1100-4. doi: 10.1038/ejhg.2013.17. Epub 2013 Feb 13. Citation on PubMed or Free article on PubMed Central
• Asadollahi R, Zweier M, Gogoll L, Schiffmann R, Sticht H, Steindl K, Rauch A. Genotype-phenotype evaluation of MED13L defects in the light of a novel truncating and a recurrent missense mutation. Eur J Med Genet. 2017 Sep;60(9):451-464. doi: 10.1016/j.ejmg.2017.06.004. Epub 2017 Jun 21. Citation on PubMed
• Cafiero C, Marangi G, Orteschi D, Ali M, Asaro A, Ponzi E, Moncada A, Ricciardi S, Murdolo M, Mancano G, Contaldo I, Leuzzi V, Battaglia D, Mercuri E, Slavotinek AM, Zollino M. Novel de novo heterozygous loss-of-function variants in MED13L and further delineation of the MED13L haploinsufficiency syndrome. Eur J Hum Genet. 2015 Nov;23(11):1499-504. doi: 10.1038/ejhg.2015.19. Epub 2015 Feb 25. Citation on PubMed or Free article on PubMed Central
• Smol T, Petit F, Piton A, Keren B, Sanlaville D, Afenjar A, Baker S, Bedoukian EC, Bhoj EJ, Bonneau D, Boudry-Labis E, Bouquillon S, Boute-Benejean O, Caumes R, Chatron N, Colson C, Coubes C, Coutton C, Devillard F, Dieux-Coeslier A, Doco-Fenzy M, Ewans LJ, Faivre L, Fassi E, Field M, Fournier C, Francannet C, Genevieve D, Giurgea I, Goldenberg A, Green AK, Guerrot AM, Heron D, Isidor B, Keena BA, Krock BL, Kuentz P, Lapi E, Le Meur N, Lesca G, Li D, Marey I, Mignot C, Nava C, Nesbitt A, Nicolas G, Roche-Lestienne C, Roscioli T, Satre V, Santani A, Stefanova M, Steinwall Larsen S, Saugier-Veber P, Picker-Minh S, Thuillier C, Verloes A, Vieville G, Wenzel M, Willems M, Whalen S, Zarate YA, Ziegler A, Manouvrier-Hanu S, Kalscheuer VM, Gerard B, Ghoumid J. MED13L-related intellectual disability: involvement of missense variants and delineation of the phenotype. Neurogenetics. 2018 May;19(2):93-103. doi: 10.1007/s10048-018-0541-0. Epub 2018 Mar 6. Citation on PubMed
• van Haelst MM, Monroe GR, Duran K, van Binsbergen E, Breur JM, Giltay JC, van Haaften G. Further confirmation of the MED13L haploinsufficiency syndrome. Eur J Hum Genet. 2015 Jan;23(1):135-8. doi: 10.1038/ejhg.2014.69. Epub 2014 Apr 30. Citation on PubMed or Free article on PubMed Central
• Yamamoto T, Shimojima K, Ondo Y, Shimakawa S, Okamoto N. MED13L haploinsufficiency syndrome: A de novo frameshift and recurrent intragenic deletions due to parental mosaicism. Am J Med Genet A. 2017 May;173(5):1264-1269. doi: 10.1002/ajmg.a.38168. Epub 2017 Mar 29. Citation on PubMed