The inclusion of craniosynostosis as a possible phenotype in KRAS-associated Noonan Syndrome has implications in the differential diagnosis and surgical management of individuals with craniosynostosis.
Metopic suture involvement has not been described before, expanding the main different cranial sutures which can be affected in NS and KRAS gene mutations.
Germline KRAS mutations were shown recently to be associated with developmental disorders, including Noonan syndrome (NS), cardio-facio-cutaneous syndrome (CFCS), and Costello syndrome (CS).
Noonan syndrome-associated mutations V14I and T58IK-Ras activate Ras but have milder biochemical effects than somatic mutations encountered in cancers, offering an explanation why these K-Ras lesions are tolerated during embryonic development.
We further defined the phenotypic spectrum associated with KRAS missense mutations and provided the first evidence of clinical differences in patients with KRAS mutations compared with Noonan syndrome affected individuals with heterozygous PTPN11 mutations and CFC patients carrying a BRAF, MEK1 or MEK1 alteration, respectively.
Somatic KRAS mutations are often detected in patients with solid and non-solid tumors, whereas germline KRAS mutations are implicated in patients with the Noonan syndrome, cardio-facio-cutaneous (CFC) syndrome and Costello syndrome.
The etiology of Noonan syndrome (NS) has been greatly elucidated with the discovery of the disease causative genes PTPN11, KRAS, SOS1, and RAF1, all involved in the RAS/MAPK-signaling cascade.
Anthropometric measurements (mean of 4.3 measurements per patient) were obtained in a mixed cross-sectional and longitudinal mode from 127 NS and 10 NLS patients with mutations identified in PTPN11 (n = 90), SOS1 (n = 14), RAF1 (n = 10), KRAS (n = 8), BRAF (n = 11), and SHOC2 (n = 4) genes.
We report on a novel KRAS gene mutation in a patient presenting the clinical features typical of Costello syndrome and the additional findings seen in Noonan syndrome.
Recently, six patients with craniosynostosis and Noonan syndrome involving KRAS mutations were described in a review, and a patient with craniosynostosis and Noonan syndrome involving a SHOC2 mutation has also been reported.
Germline mutations in genes encoding small GTPases of the RAS family (KRAS and NRAS), modulators of RAS function (PTPN11, SOS1 and SHOC2) or downstream signal transducers (RAF1) are causative for NS.
We have observed unusual transverse distal phalangeal creases in two patients, one with Costello syndrome (G12S mutation in the HRAS gene) and one with cardio-facio-cutaneous (CFC) syndrome or possibly Noonan syndrome (Q22E mutation in the KRAS gene).
PTPN11 (39.0%), SOS1 (20.3%), RAF1 (6.8%), KRAS (5.1%), and BRAF (1.7%) mutations were identified in NS; BRAF (41.2%), SHOC2 (23.5%), and MEK1 (5.9%) mutations in cardiofaciocutaneous syndrome; and HRAS and PTPN11 mutations in Costello syndrome and LEOPARD syndrome, respectively.
In conclusion, this investigation demonstrates that KRAS mutations are the cause in a minority of cases of Chinese patients with Noonan syndrome in Taiwan.
Here, we report a crystal structure of GDP-bound KRAS<sup>V14I</sup>, a mutated KRAS variant associated with the developmental RASopathy disorder Noonan syndrome (NS), at 1.5-1.6 Å resolution.
Gene-related Chinese NS facial features were described using artificial intelligence (AI).NGS identified pathogenic variants in 103 Chinese patients in eight NS-related genes: PTPN11 (48.5%), SOS1 (12.6%), SHOC2 (11.7%), KRAS (9.71%), RAF1 (7.77%), RIT1 (6.8%), CBL (0.97%), NRAS (0.97%), and LZTR1 (0.97%).