Noonan and Ras/Mapk Pathway Syndromes
Short Description or Definition
Noonan syndrome (NS) is a multiple malformation genetic disorder characterized by dysmorphic facies including hypertelorism, ptosis, low-set posteriorly rotated ears, short neck, and relative macrocephaly. Associated features include short stature, chest deformity, undescended testes, muscle hypotonia, frequent learning difficulties, and congenital heart disease most commonly valvular pulmonary stenosis. In 2001 (Tartaglia et al., 2001), a germline mutation in the PTPN11 gene in the Ras/MAPK (mitogen-activated protein kinase) signal transduction pathway was found to be a cause of nearly 50% of the cases of NS. Since then a number of other genes in the same pathway have been identified but in about 25% the causative gene for NS has yet to be identified.
Before NS was recognized as a distinct syndrome some females were misdiagnosed as having Turner syndrome and many males, given the diagnosis of male...
References and Readings
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