Patients with the HRAS mutation c.173C>T (p.T58I) might go undiagnosed because of the milder phenotype compared with other mutations causing Costello syndrome.
Panel testing for rasopathies identified a novel HRAS mutation (c.179G>A; p.Gly60Asp) in three individuals with attenuated features of Costello syndrome.
Costello syndrome (CS) is a rare genetic disorder caused, in the majority of cases, by germline missense HRAS mutations affecting Gly(12) promoting enhanced signaling through the MAPK and PI3K-AKT signaling cascades.
One of these conditions, Costello syndrome (CS), is typically caused by an activating de novo germline mutation in HRAS and is characterized by a wide range of cardiac, musculoskeletal, dermatological and developmental abnormalities.
Here, we report on a novel heterozygous HRAS germline mutation (c.187_207dup, p.E63_D69dup) in a girl presenting with a phenotype at the milder end of the Costello syndrome spectrum.
Other less common lesions in HRAS can induce a milder phenotype on the one hand and a more severe phenotype on the other broadening the spectrum of clinical manifestations in CS-affected individuals.
Costello syndrome is caused by HRAS germline mutations affecting Gly(12) or Gly(13) in >90% of cases and these are associated with a relatively homogeneous phenotype.
Several studies have shown that CS-associated HRAS mutations are clustered in codons 12 and 13, and mutations in other codons have also been identified.
Duplication of Glu37 in the switch I region of HRAS impairs effector/GAP binding and underlies Costello syndrome by promoting enhanced growth factor-dependent MAPK and AKT activation.
Duplication of Glu37 in the switch I region of HRAS impairs effector/GAP binding and underlies Costello syndrome by promoting enhanced growth factor-dependent MAPK and AKT activation.
We report a patient with typical Costello syndrome and a novel heterozygous missense mutation in codon 117 (c.350A>G, p.Lys117Arg) of the HRAS gene, resulting in constitutive activation of the RAS/MAPK pathway similar to the typical p.Gly12Ser and p.Gly12Ala mutations.
This led us to review the medical histories on a cohort of proven HRAS mutation positive Costello syndrome patients, and we found a statistically significantly (P < 0.001) increased frequency of pyloric stenosis in Costello syndrome (5/58) compared to the general population frequency of 2-3/1,000.
However, some patients carrying HRAS mutations may exhibit prominent congenital muscular dysfunction, although features of CS may be less obvious, suggesting that germline HRAS mutations may underlie some cases of otherwise unclassified neonatal neuromuscular disorders.
However, some patients carrying HRAS mutations may exhibit prominent congenital muscular dysfunction, although features of CS may be less obvious, suggesting that germline HRAS mutations may underlie some cases of otherwise unclassified neonatal neuromuscular disorders.