Daniel Doyle

HRAS mutation analysis in Costello syndrome: Genotype and phenotype correlation

Costello syndrome is a rare condition comprising mental retardation, distinctive facial appearance, cardiovascular abnormalities (typically pulmonic stenosis, hypertrophic cardiomyopathy, and/or atrial tachycardia), tumor predisposition, and skin and musculoskeletal abnormalities. Recently mutations in HRAS were identified in 12 Japanese and Italian patients with clinical information available on 7 of the Japanese patients. To expand the molecular delineation of Costello syndrome, we performed mutation analysis in 34 North American and 6 European (total 40) patients with Costello syndrome, and detected missense mutations in HRAS in 33 (82.5%) patients. All mutations affected either codon 12 or 13 of the protein product, with G12S occurring in 30 (90.9%) patients of the mutation‐positive cases. In two patients, we found a mutation resulting in an alanine substitution in position 12 (G12A), and in one patient, we detected a novel mutation (G13C). Five different HRAS mutations have now been reported in Costello syndrome, however genotype–phenotype correlation remains incomplete.

High incidence of progressive postnatal cerebellar enlargement in Costello syndrome: Brain overgrowth associated with HRAS mutations as the likely cause of structural brain and spinal cord abnormalities†

Costello syndrome is a rasopathy caused by germline mutations in the proto‐oncogene HRAS. Its presentation includes failure‐to‐thrive with macrocephaly, characteristic facial features, hypertrophic cardiomyopathy, papillomata, malignant tumors, and cognitive impairment. In a systematic review we found absolute or relative macrocephaly (100%), ventriculomegaly (50%), and other abnormalities on brain and spinal cord imaging studies in 27/28 individuals. Posterior fossa crowding with cerebellar tonsillar herniation (CBTH) was noted in 27/28 (96%), and in 10/17 (59%) with serial studies posterior fossa crowding progressed. Sequelae of posterior fossa crowding and CBTH included hydrocephalus requiring shunt or ventriculostomy (25%), Chiari 1 malformation (32%), and syrinx formation (25%). Our data reveal macrocephaly with progressive frontal bossing and CBTH, documenting an ongoing process rather than a static congenital anomaly. Comparison of images obtained in young infants to subsequent studies demonstrated postnatal development of posterior fossa crowding. This process of evolving megalencephaly and cerebellar enlargement is in keeping with mouse model data, delineating abnormal genesis of neurons and glia, resulting in an increased number of astrocytes and enlarged brain volume. In Costello syndrome and macrocephaly‐capillary malformation syndrome disproportionate brain growth is the main factor resulting in postnatal CBTH and Chiari 1 malformation.

Costello syndrome associated with novel germline HRAS mutations: An attenuated phenotype?

Costello syndrome is a rare congenital disorder typically characterized by severe failure‐to‐thrive, cardiac abnormalities including tachyarrhythmia and hypertrophic cardiomyopathy, distinctive facial features, a predisposition to papillomata and malignant tumors, neurologic abnormalities, developmental delay, and mental retardation. Its underlying cause is de novo germline mutations in the oncogene HRAS. Almost all Costello syndrome mutations affect one of the glycine residues in position 12 or 13 of the protein product. More than 80% of patients with Costello syndrome share the same underlying mutation, resulting in a G12S amino acid change. We report on two patients with novel HRAS mutations affecting amino acids 58 (T58I) and 146 (A146V), respectively. Despite facial features that appear less coarse than those typically seen in Costello patients, both patients show many of the physical and developmental problems characteristic for Costello syndrome. These novel HRAS mutations may be less common than the frequently reported G12S change, or patients with these changes may be undiagnosed due to their less coarse facial features. In addition to the findings previously known to occur in Costello syndrome, one of our patients had hypertrophic pyloric stenosis. 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. Thus we add hypertrophic pyloric stenosis to the abnormalities seen with increased frequency in Costello syndrome.

Phenotypic analysis of individuals with Costello syndrome due to HRAS p.G13C

Costello syndrome is characterized by severe failure‐to‐thrive, short stature, cardiac abnormalities (heart defects, tachyarrhythmia, and hypertrophic cardiomyopathy (HCM)), distinctive facial features, a predisposition to papillomata and malignant tumors, postnatal cerebellar overgrowth resulting in Chiari 1 malformation, and cognitive disabilities. De novo germline mutations in the proto‐oncogene HRAS cause Costello syndrome. Most mutations affect the glycine residues in position 12 or 13, and more than 80% of patients share p.G12S. To test the hypothesis that subtle genotype–phenotype differences exist, we report the first cohort comparison between 12 Costello syndrome individuals with p.G13C and individuals with p.G12S. The individuals with p.G13C had many typical findings including polyhydramnios, failure‐to‐thrive, HCM, macrocephaly with posterior fossa crowding, and developmental delay. Subjectively, their facial features were less coarse. Statistically significant differences included the absence of multifocal atrial tachycardia (P‐value = 0.033), ulnar deviation of the wrist (P < 0.001) and papillomata (P = 0.003), and fewer neurosurgical procedures (P = 0.024). Fewer individuals with p.G13C had short stature (height below −2 SD) without use of growth hormone (P < 0.001). The noteworthy absence of malignant tumors did not reach statistical significance. Novel ectodermal findings were noted in individuals with p.G13C, including loose anagen hair resulting in easily pluckable hair with a matted appearance, different from the tight curls typical for most Costello syndrome individuals. Unusually long eye lashes requiring trimming are a novel finding we termed dolichocilia. These distinctive ectodermal findings suggest a cell type specific effect of this particular mutation. Additional patients are needed to validate these findings.

Growth hormone treatment and pseudotumor cerebri: coincidence or close relationship?

Pseudotumor cerebri (PTC) is an uncommon disorder in the pediatric population. It is not a benign condition. It can cause permanent vision loss. The most recently recognized risk factor for this disorder is recombinant human growth hormone (GH) therapy. Data from Genentechs National Cooperative Growth Study (NCGS), a postmarketing surveillance program, are analyzed to examine the relationship between GH therapy and PTC. Several areas are addressed, including plausibility, probability, clinical and laboratory presentations, management, clinical outcome, present state of knowledge, and future recommendations.

Molecular aspects, clinical aspects and possible treatment modalities for Costello syndrome: Proceedings from the 1st International Costello Syndrome Research Symposium 2007.

Katherine A. Rauen,* Erin Hefner, Kristin Carrillo, Jill Taylor, Laure Messier, Yoko Aoki, Karen W. Gripp, Yoichi Matsubara, Virginia K. Proud, Peter Hammond, Judith E. Allanson, Marie-Ange Delrue, Marni E. Axelrad, Angela E. Lin, Daniel A. Doyle, Bronwyn Kerr, John C. Carey, Frank McCormick, Alcino J. Silva, Mark W. Kieran, Aleksander Hinek, Tan T. Nguyen, and Lisa Schoyer Department of Pediatrics, Division of Medical Genetics, University of California, San Francisco, California UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, California Costello Syndrome Family Network, Altadena, California Department of Medical Genetics, Tohoku University School of Medicine, Sendai, Japan Division of Medical Genetics, Alfred I. DuPont Hospital for Children, Wilmington, Delaware Children’s Hospital of the King’s Daughters, Norfolk, Virginia Molecular Medicine Unit, Institute of Child Health, UCL, London, UK Children’s Hospital of Eastern Ontario, Ontario, Canada Department of Medical Genetics, Centre Hospitalier Pellegrin Enfant, Bordeaux University, Bordeaux, France Learning Support Center for Child Psychology, Department of Pediatrics, Texas Children’s Hospital, Houston, Texas Genetics Unit, MassGeneral Hospital for Children, Boston, Massachusetts Division of Endocrinology, Alfred I. duPont Hospital for Children, Wilmington, Delaware Academic Unit of Medical Genetics, St. Mary’s Hospital, Manchester, UK Department of Pediatrics, Division of Medical Genetics, University of Utah Health Sciences Center, Salt Lake City, Utah Departments of Neurobiology, Psychology, and Psychiatry, Brain Research Institute, UCLA, Los Angeles, California Dana-Farber Cancer Institute, Department of Pediatric Oncology, Boston, Massachusetts Division of Cardiovascular Research, Hospital for Sick Children, Toronto, Canada Office of Orphan Products Development, Food and Drug Administration, Rockville, Maryland

A novel mutation in the GCM2 gene causing severe congenital isolated hypoparathyroidism.

Abstract Objective: To investigate the GCM2 gene in three siblings with congenital hypoparathyroidism and perform functional analysis. Materials and methods: We sequenced the GCM2 gene by PCR and analyzed the functional consequence of the mutation by transient transfection studies. Haplotype analysis was performed. Results: We identified a nucleotide change, c.408C>A, in exon 3 that is predicted to truncate the Gcm2 protein (p.Tyr136Ter). All three affected siblings were homozygous and both parents were heterozygous for the mutation. Transfection studies revealed the mutant mRNA but not expression of the Gcm2 protein. Haplotype analysis revealed that the two mutant GCM2 alleles shared genotypes on chromosome 6p24.2. Conclusions: We describe the first GCM2 mutation in exon 3 in patients with severe congenital hypoparathyroidism. Informative genetic markers could not exclude identity by descent for the mutant alleles. Gcm2 protein was not detected after transfection, suggesting that complete lack of Gcm2 action accounts for severe hypoparathyroidism.

Idiopathic infantile hypercalcemia: case report and review of the literature.

Abstract The widespread use of supplemental vitamin D has dramatically reduced the incidence of rickets. While generally considered a safe practice, there is potential for toxicity in patients with idiopathic infantile hypercalcemia (IIH). Inadequate 24-hydroxylase-enzyme activity renders these individuals unable to degrade active vitamin D, resulting in hypercalcemia due to increased intestinal calcium absorption, decreased renal calcium excretion, and increased osteoclastic bone activity. Clinicians should be aware that even therapeutic doses of vitamin D can prove harmful for patients with CYP24A1 mutations. Studies have also demonstrated a link between inadequate 24-hydroxylase activity and nephrocalcinosis, renal insufficiency, and calcium containing kidney stones, further emphasizing the importance of early recognition of this disease and judicious use of vitamin D. We present a case with an interesting diagnostic algorithm used to diagnose IIH when given an incomplete history and subsequently review the existing literature on the subject.

Phenotypic spectrum of Costello syndrome individuals harboring the rare HRAS mutation p.Gly13Asp

Costello syndrome is part of the RASopathies, a group of neurocardiofaciocutaneous syndromes caused by deregulation of the RAS mitogen‐activated protein kinase pathway. Heterozygous mutations in HRAS are responsible for Costello syndrome, with more than 80% of the patients harboring the specific p.Gly12Ser variant. These individuals show a homogeneous phenotype. The clinical characteristics of the Costello syndrome individuals harboring rarer HRAS mutations are less understood, due to the small number of reported cases. Here, we describe the phenotypic spectrum of five additional individuals with HRAS c.38G>A; p.Gly13Asp, including one with somatic mosaicism, and review five previously described cases. The facial and hair abnormalities of the HRAS p.Gly13Asp individuals differ from the typical pattern observed in those showing the common HRAS (p.Gly12Ser) mutation, with less coarse facial features and slow growing, sparse hair with abnormal texture, the latter resembling the pattern observed in Noonan syndrome‐like disorder with loose anagen hair and individuals harboring another amino acid substitution in HRAS (p.Gly13Cys). Although some individuals with HRAS p.Gly13Asp developed papillomata and vascular proliferation lesions, no malignant tumors occurred, similar to what was reported for individuals harboring the HRAS p.Gly13Cys. The fact that no malignant tumors were described in these individuals does not allow definitive conclusions about the risk for cancer development. It remains to be determined if substitutions of amino acid 13 in HRAS (p.Gly13Asp and p.Gly13Cys) increase the risk of tumor development.