What are the symptoms? Characteristics of Noonan syndrome include: heart defects – the most common being pulmonary valve stenosis, atrial septal defects (see entry Heart Defects) and hypertrophic cardiomyopathy (see entry Cardiomyopathies)characteristic facial features, including ptosis (drooping eyelids), hypertelorism (widely spaced eyes), large downward-slanting eyes, flat nasal bridge and short neck with neck webbing and anterior rotation (slanting forwards) of the earsshort stature. Additional features may include: excess oedema (fluid retention in the body) at birth and slow weight gainfeeding difficulties with poor sucking and weaning and frequent and/or forceful vomiting in babies which may be assessed as failure to thrivemild hearing lossdental delayelevated or depressed sternumhypotoniaundescended testes (meaning that the testicles stay within the abdomen)mild developmental delay in a small number of childrenspeech and behaviour problems. In addition, the characteristics of the syndrome, especially facial, appear to change as the individual ages. Overlapping syndromesLEOPARD syndrome, CFC syndrome (see entry cardiofaciocutaneous syndrome), Costello syndrome and neurofibromatosis are all due to defects in the same pathway and have different clinical features. However LEOPARD syndrome is the most similar and due to changes in the same gene PTPN11. The term LEOPARD syndrome stands for: Lentignes (freckles)Electrocardiogram (minor abnormalities in the electrical activity of the heart)Ocular hypertelorism (widely spaced eyes)Pulmonary stenosisAbnormalities of the male genitaliaRetardation of growthDeafness. Inheritance patterns and prenatal diagnosis Inheritance patternsAutosomal dominant. A gene PTPN11 on chromosome 12 has been found to account for half of all cases of Noonan syndrome. Other genes that may cause Noonan syndrome include SOS1, KRAS and SHOC2. Molecular testing is now available. Prenatal diagnosisPrenatal diagnosis is available by molecular testing if the mutation has been identified. Occasionally it may be diagnosed by the presence of cystic hygroma or fetal hydrops in the womb (where fluid accumulates in certain parts of the unborn baby). Is there support? Noonan Syndrome Association Email: firstname.lastname@example.orgWebsite: noonansyndrome.org.uk Noonan Syndrome Association (NSA) is a Registered Charity in England and Wales No. 1140671. The NSA supports patients and families affected by Noonan Syndrome through research, nurse services, national and regional events, publications and raising awareness of the condition. Group details last updated August 2021.