High frequency of hotspot mutation in PTPN11 gene among Moroccan patients with Noonan syndrome

Noonan syndrome (NS; OMIM 163950) is an autosomal dominant RASopathy with variable clinical expression and genetic heterogeneity. Clinical manifestations include characteristic facial features, short stature, and cardiac anomalies. Variants in protein-tyrosine phosphatase, non-receptor-type 11 (PTPN11), encoding SHP-2, account for about half of NS patients, SOS1 in approximately 13%, RAF1 in 10%, and RIT1 each in 9%. Other genes have been reported to cause NS in less than 5% of cases including SHOC2, RASA2, LZTR1, SPRED2, SOS2, CBL, KRAS, NRAS, MRAS, PRAS, BRAF, PPP1CB, A2ML1, MAP2K1, and CDC42. Several additional genes associated with a Noonan syndrome-like phenotype have been identified. Clinical presentation and variants in patients with Noonan syndrome are this study's objectives. We performed Sanger sequencing of PTPN11 hotspot (exons 3, 8, and 13). We report molecular analysis of 61 patients with NS phenotype belonging to 58 families. We screened for hotspot variants (exons 3, 8, and 13) in PTPN11 gene by Sanger sequencing. Twenty-seven patients were carrying heterozygous pathogenic variants of PTPN11 gene with a similar frequency (41.4%) compared to the literature. Our findings expand the variant spectrum of Moroccan patients with NS phenotype in whom the analysis of hotspot variants showed a high frequency of exons 3 and 8. This screening test allowed us to establish a molecular diagnosis in almost half of the patients with a good benefit-cost ratio, with appropriate management and genetic counseling.

Mutations in PTPN11 could lead to a congenital myasthenic syndrome phenotype: a Noonan syndrome case series

The RASopathies are a group of genetic rare diseases caused by mutations affecting genes involved in the RAS/MAPK (RAS-mitogen activated protein kinase) pathway. Among them, PTPN11 pathogenic variants are responsible for approximately 50% of Noonan syndrome (NS) cases and, albeit to a lesser extent, of Leopard syndrome (LPRD1), which present a few overlapping clinical features, such as facial dysmorphism, developmental delay, cardiac defects, and skeletal deformities. Motor impairment and decreased muscle strength have been recently reported. The etiology of the muscle involvement in these disorders is still not clear but probably multifactorial, considering the role of the RAS/MAPK pathway in skeletal muscle development and Acetylcholine Receptors (AChR) clustering at the neuromuscular junction (NMJ). We report, herein, four unrelated children carrying three different heterozygous mutations in the PTPN11 gene. Intriguingly, their phenotypic features first led to a clinical suspicion of congenital myasthenic syndrome (CMS), due to exercise-induced fatigability with a variable degree of muscle weakness, and serum proteomic profiling compatible with a NMJ defect. Moreover, muscle fatigue improved after treatment with CMS-specific medication. Although the link between PTPN11 gene and neuromuscular transmission is unconfirmed, an increasing number of patients with RASopathies are affected by muscle weakness and fatigability. Hence, NS or LPDR1 should be considered in children with suspected CMS but negative genetic workup for known CMS genes or additional symptoms indicative of NS, such as facial dysmorphism or intellectual disability.

The RRAS2 pathogenic variant (c.67G>T; p. Gly23Cys) produces Noonan syndrome with embryonal rhabdomyosarcoma

BACKGROUND

Noonan syndrome (NS) due to the RRAS2 gene, the pathogenic variant is an extremely rare RASopathies. Our objective was to identify the potential site of RRAS2, combined with the literature review, to find the correlation between clinical phenotype and genotype. De novo missense mutations affect different aspects of the RRAS2 function, leading to hyperactivation of the RAS-MAPK signaling cascade.

METHODS

Conventional G-banding was used to analyze the chromosome karyotype of the patient. Copy number variation sequencing (CNV-seq) was used to detect the chromosomal gene microstructure of the patient and her parents. The exomes of the patient and her parents were sequenced using trio-based whole exome sequencing (trio-WES) technology. The candidate variant was verified by Sanger sequencing. The pathogenicity of the variant was predicted with a variety of bioinformatics tools.

RESULTS

Chromosome analysis of the proband revealed 46, XX, and no abnormality was found by CNV-seq. After sequencing and bioinformatics filtering, the variant of RRAS2(c.67G>T; p. Gly23Cys) was found in the proband, while the mutation was absent in her parents. To the best of our knowledge, our patient was with the typical Noonan syndrome, such as short stature, facial dysmorphism, and developmental delay. Furthermore, our study is the first case of NS with embryonal rhabdomyosarcoma (ERMS) caused by the RRAS2 gene mutation reported in China.

CONCLUSIONS

Our investigations suggested that the heterozygous missense of RRAS2 may be a potential causal variant in a rare cause of Noonan syndrome, expanding our understanding of the causally relevant mutations for this disorder.

A very mild phenotype in six individuals of a three-generation family with the novel HRAS variant c.176C > G p.(Ala59Gly): Emergence of a new HRAS-related RASopathy distinct from Costello syndrome

Costello syndrome is a clinically recognizable, severe neurodevelopmental disorder caused by heterozygous activating variants in HRAS. The vast majority of affected patients share recurring variants affecting HRAS codons 12 and 13 and a relatively uniform phenotype. Here, we report the unique and attenuated phenotype of six individuals of an extended family affected by the HRAS variant c.176C>T p.(Ala59Gly), which, to our knowledge, has never been reported as a germline variant in patients so far. HRAS Alanine 59 has been previously functionally investigated as an oncogenic hotspot and the p.Ala59Gly substitution was shown to impair intrinsic GTP hydrolysis. All six individuals we report share a phenotype of ectodermal anomalies and mild features suggestive of a RASopathy, reminiscent of patients with Noonan syndrome-like disorder with loose anagen hair. All six are of normal intelligence, none have a history of failure to thrive or malignancy, and they have no known cardiac or neurologic pathologies. Our report adds to the previous reports of patients with rare variants affecting amino acids located in the SWITCH II/G3 region of HRAS and suggests a consistent, attenuated phenotype distinct from classical Costello syndrome. We propose the definition of a new distinct HRAS-related RASopathy for patients carrying HRAS variants affecting codons 58, 59, 60.

RAS-dependent RAF-MAPK hyperactivation by pathogenic RIT1 is a therapeutic target in Noonan syndrome-associated cardiac hypertrophy

RIT1 is a RAS guanosine triphosphatase (GTPase) that regulates different aspects of signal transduction and is mutated in lung cancer, leukemia, and in the germline of individuals with Noonan syndrome. Pathogenic RIT1 proteins promote mitogen-activated protein kinase (MAPK) hyperactivation; however, this mechanism remains poorly understood. Here, we show that RAF kinases are direct effectors of membrane-bound mutant RIT1 necessary for MAPK activation. We identify critical residues in RIT1 that facilitate interaction with membrane lipids and show that these are necessary for association with RAF kinases and MAPK activation. Although mutant RIT1 binds to RAF kinases directly, it fails to activate MAPK signaling in the absence of classical RAS proteins. Consistent with aberrant RAF/MAPK activation as a driver of disease, we show that pathway inhibition alleviates cardiac hypertrophy in a mouse model of RIT1 mutant Noonan syndrome. These data shed light on the function of pathogenic RIT1 and identify avenues for therapeutic intervention.

Cancer incidence and surveillance strategies in individuals with RASopathies

RASopathies are a set of clinical syndromes that have molecular and clinical overlap. Genetically, these syndromes are defined by germline pathogenic variants in RAS/MAPK pathway genes resulting in activation of this pathway. Clinically, their common molecular signature leads to comparable phenotypes, including cardiac anomalies, neurologic disorders and notably, elevated cancer risk. Cancer risk in individuals with RASopathies has been estimated from retrospective reviews and cohort studies. For example, in Costello syndrome, cancer incidence is significantly elevated over the general population, largely due to solid tumors. In some forms of Noonan syndrome, cancer risk is also elevated over the general population and is enriched for hematologic malignancies. Thus, cancer surveillance guidelines have been developed to monitor for the occurrence of such cancers in individuals with some RASopathies. These include abdominal ultrasound and urinalyses for individuals with Costello syndrome, while complete blood counts and splenic examination are recommended in Noonan syndrome. Improved cancer risk estimates and refinement of surveillance recommendations will improve the care of individuals with RASopathies.

Keratopathy in Noonan Syndrome

PURPOSE

Anterior segment abnormalities associated with Noonan syndrome are rare. We report our experience with 2 patients who developed keratopathy with significant visual sequelae.

METHODS

case series.

RESULTS

The first patient is a 9-year-old boy with genetically confirmed Noonan syndrome. At presentation, he was noted to have diffuse inferior epitheliopathy with vascularization and bilateral mild ptosis. Over 1 year, he developed focal areas of scarring with deterioration of vision and underwent superficial keratectomy in the left eye. However, over the following 2 years, he experienced recurrent corneal scarring and vascularization. The second patient is a 7-year-old boy with phenotypic Noonan syndrome. At presentation, he had an anterior subepithelial corneal scar inferiorly with epithelial defects in both eyes. He also had bilateral moderate ptosis and lagophthalmos. Despite lubrication, he developed recurrent bilateral corneal erosions with focal areas of scarring associated with vascularization and underwent superficial keratectomy for both eyes. Despite this, there was worsening corneal scarring and vascularization over time, eventually requiring deep anterior lamellar keratoplasty in the left eye. The host cornea showed a disturbed Bowman layer and an acellular mass of fibrous collagenous tissue between epithelium and stroma.

CONCLUSIONS

Noonan syndrome may be associated with visually significant keratopathy, manifesting as focal corneal scarring with vascularization. These changes may due to an excessive fibrotic response in Noonan syndrome. Early recognition and treatment can help to delay the progression of keratopathy and need for surgical intervention.

Effects of Noonan Syndrome-Germline Mutations on Mitochondria and Energy Metabolism

Noonan syndrome (NS) and related Noonan syndrome with multiple lentigines (NSML) contribute to the pathogenesis of human diseases in the RASopathy family. This family of genetic disorders constitute one of the largest groups of developmental disorders with variable penetrance and severity, associated with distinctive congenital disabilities, including facial features, cardiopathies, growth and skeletal abnormalities, developmental delay/mental retardation, and tumor predisposition. NS was first clinically described decades ago, and several genes have since been identified, providing a molecular foundation to understand their physiopathology and identify targets for therapeutic strategies. These genes encode proteins that participate in, or regulate, RAS/MAPK signalling. The RAS pathway regulates cellular metabolism by controlling mitochondrial homeostasis, dynamics, and energy production; however, little is known about the role of mitochondrial metabolism in NS and NSML. This manuscript comprehensively reviews the most frequently mutated genes responsible for NS and NSML, covering their role in the current knowledge of cellular signalling pathways, and focuses on the pathophysiological outcomes on mitochondria and energy metabolism.

A Chinese family with Noonan syndrome caused by a heterozygous variant in LZTR1: a case report and literature review

BACKGROUND

Noonan syndrome is an inherited disease involving multiple systems. More than 15 related genes have been discovered, among which LZTR1 was discovered recently. However, the pathogenesis and inheritance pattern of LZTR1 in Noonan syndrome have not yet been elucidated.

CASE PRESENTATION

We herein describe a family with LZTR1-related Noonan syndrome. In our study, the proband, sister, mother, maternal aunt and grandmother and female cousin showed the typical or atypical features of Noonan syndrome. Only 3 patients underwent the whole-exome sequencing analysis and results showed that the proband as well as her sister inherited the same heterozygous LZTR1 variant (c.1149 + 1G > T) from their affected mother. Moreover, the proband accompanied by growth hormone deficiency without other associated variants.

CONCLUSION

In a Chinese family with Noonan syndrome, we find that the c.1149 + 1G > T variant in LZTR1 gene shows a different autosomal dominant inheritance from previous reports, which changes our understanding of its inheritance and improves our understanding of Noonan syndrome.

Oskar Kobyliński (1856-1926) and the first description of Noonan syndrome in the medical literature

While a student of University in Dorpat (now Tartu, Estonia) Oskar Kobyliński published an article reporting on his 22-year-old patient Leisar Eischikmann, who suffered from a congenital deformity of the neck. Kobyliński described this rare anomaly and called it "flüghautige Verbreitung des Halses" (wing-like extension of the neck). It was only in 1902 when the name pterygium colli was introduced, and it has been in use ever since. This malformation is part of some congenital syndromes, most prominently, Turner syndrome and, more rarely, of Noonan syndrome. As Opitz et al. pointed out, the patient described in the 1883 article from Archiv für Anthropologie is probably the first person with Noonan syndrome to have been pictured in the medical literature. The article was signed only by "O. v. Kobylinski, student of medicine." Further archival research was needed to identify this physician and provide more details about his unusual career.

M-Ras is Muscle-Ras, Moderate-Ras, Mineral-Ras, Migration-Ras, and Many More-Ras

The Ras family of small GTPases comprises about 36 members in humans. M-Ras is related to classical Ras with regard to its regulators and effectors, but solely constitutes a subfamily among the Ras family members. Although classical Ras strongly binds Raf and highly activates the ERK pathway, M-Ras less strongly binds Raf and moderately but sustainedly activates the ERK pathway to induce neuronal differentiation. M-Ras also possesses specific effectors, including RapGEFs and the PP1 complex Shoc2-PP1c, which dephosphorylates Raf to activate the ERK pathway. M-Ras is highly expressed in the brain and plays essential roles in dendrite formation during neurogenesis, in contrast to the axon formation by R-Ras. M-Ras is also highly expressed in the bone and induces osteoblastic differentiation and transdifferentiation accompanied by calcification. Moreover, M-Ras elicits epithelial-mesenchymal transition-mediated collective and single cell migration through the PP1 complex-mediated ERK pathway activation. Activating missense mutations in the MRAS gene have been detected in Noonan syndrome, one of the RASopathies, and MRAS gene amplification occurs in several cancers. Furthermore, several SNPs in the MRAS gene are associated with coronary artery disease, obesity, and dyslipidemia. Therefore, M-Ras carries out a variety of cellular, physiological, and pathological functions. Further investigations may reveal more functions of M-Ras.

Comprehensive Genomic Analysis of Noonan Syndrome and Acute Myeloid Leukemia in Adults: A Review and Future Directions

Acute myeloid leukemia (AML) in the setting of Noonan syndrome (NS) has been reported before without clear guidelines for treatment or prognosis in these subgroups of patients, most likely due to its rarity and incomplete understanding of the pathogenesis of both diseases. In the current era of next-generation sequencing-based genomic analysis, we can better identify patients with NS with more accurate AML-related prognostic markers. Germline mutations in PTPN11 are the most common cause of NS. Somatic mutations in NPM1 occur frequently in AML. Here, we describe a young adult patient with a novel combined germline PTPN11 and somatic NPM1, IDH1,and BCL6 mutations who presented with fatal AML. In addition, a 50.5-Mb interstitial deletion of 7q21.11-q33 in tumor DNA was detected by chromosomal microarray analysis. While mutations in the transcriptional repressor BCL6 are known to contribute to the pathogenesis of diffuse large B cell lymphoma (DLBCL) and chronic lymphocytic leukemia (CLL), its novel identification in this patient suggests an expanded role in aggressive AML. The identification of key molecular aberrations including the overexpression of SHP2, which drives leukemogenesis and tumorigenesis, has led to the development of novel investigational targeted SHP2 inhibitors.

Complicated ventricular arrhythmia and hematologic myeloproliferative disorder in RIT1-associated Noonan syndrome: Expanding the phenotype and review of the literature

Background

Noonan syndrome is an autosomal dominant disorder secondary to RASopathies, which are caused by germ‐line mutations in genes encoding components of the RAS mitogen‐activated protein kinase pathway. RIT1 (OMIM *609591) was recently reported as a disease gene for Noonan syndrome.

Methods and Results

We present a patient with RIT1‐associated Noonan syndrome, who in addition to the congenital heart defect, had monocytosis, myeloproliferative disorder, and accelerated idioventricular rhythm that was associated with severe hemodynamic instability. Noonan syndrome was suspected given the severe pulmonary stenosis, persistent monocytosis, and “left‐shifted” complete blood counts without any evidence of an infectious process. Genetic testing revealed that the patient had a heterozygous c.221 C>G (pAla74Gly) mutation in the RIT1.

Conclusion

We report a case of neonatal Noonan syndrome associated with RIT1 mutation. The clinical suspicion for Noonan syndrome was based only on the congenital heart defect, persistent monocytosis, and myeloproliferative process as the child lacked all other hallmarks characteristics of Noonan syndrome. However, the patient had an unusually malignant ventricular dysrhythmia that lead to his demise. The case highlights the fact that despite its heterogeneous presentation, RIT1‐associated Noonan syndrome can be extremely severe with poor outcome.

The Noonan Syndrome Gene Lztr1 Controls Cardiovascular Function by Regulating Vesicular Trafficking

RATIONALE

Noonan syndrome (NS) is one of the most frequent genetic disorders. Bleeding problems are among the most common, yet poorly defined complications associated with NS. A lack of consensus on the management of bleeding complications in patients with NS indicates an urgent need for new therapeutic approaches.

OBJECTIVE

Bleeding disorders have recently been described in patients with NS harboring mutations of LZTR1 (leucine zipper-like transcription regulator 1), an adaptor for CUL3 (CULLIN3) ubiquitin ligase complex. Here, we assessed the pathobiology of LZTR1-mediated bleeding disorders.

METHODS AND RESULTS

Whole-body and vascular specific knockout of Lztr1 results in perinatal lethality due to cardiovascular dysfunction. Lztr1 deletion in blood vessels of adult mice leads to abnormal vascular leakage. We found that defective adherent and tight junctions in Lztr1-depleted endothelial cells are caused by dysregulation of vesicular trafficking. LZTR1 affects the dynamics of fusion and fission of recycling endosomes by controlling ubiquitination of the ESCRT-III (endosomal sorting complex required for transport III) component CHMP1B (charged multivesicular protein 1B), whereas NS-associated LZTR1 mutations diminish CHMP1B ubiquitination. LZTR1-mediated dysregulation of CHMP1B ubiquitination triggers endosomal accumulation and subsequent activation of VEGFR2 (vascular endothelial growth factor receptor 2) and decreases blood levels of soluble VEGFR2 in Lztr1 haploinsufficient mice. Inhibition of VEGFR2 activity by cediranib rescues vascular abnormalities observed in Lztr1 knockout mice Conclusions: Lztr1 deletion phenotypically overlaps with bleeding diathesis observed in patients with NS. ELISA screening of soluble VEGFR2 in the blood of LZTR1-mutated patients with NS may predict both the severity of NS phenotypes and potential responders to anti-VEGF therapy. VEGFR inhibitors could be beneficial for the treatment of bleeding disorders in patients with NS.

Germline-Activating RRAS2 Mutations Cause Noonan Syndrome

Noonan syndrome (NS) is characterized by distinctive craniofacial appearance, short stature, and congenital heart disease. Approximately 80% of individuals with NS harbor mutations in genes whose products are involved in the RAS/mitogen-activating protein kinase (MAPK) pathway. However, the underlying genetic causes in nearly 20% of individuals with NS phenotype remain unexplained. Here, we report four de novo RRAS2 variants in three individuals with NS. RRAS2 is a member of the RAS subfamily and is ubiquitously expressed. Three variants, c.70_78dup (p.Gly24_Gly26dup), c.216A>T (p.Gln72His), and c.215A>T (p.Gln72Leu), have been found in cancers; our functional analyses showed that these three changes induced elevated association of RAF1 and that they activated ERK1/2 and ELK1. Notably, prominent activation of ERK1/2 and ELK1 by p.Gln72Leu associates with the severe phenotype of the individual harboring this change. To examine variant pathogenicity in vivo, we generated zebrafish models. Larvae overexpressing c.70_78dup (p.Gly24_Gly26dup) or c.216A>T (p.Gln72His) variants, but not wild-type RRAS2 RNAs, showed craniofacial defects and macrocephaly. The same dose injection of mRNA encoding c.215A>T (p.Gln72Leu) caused severe developmental impairments and low dose overexpression of this variant induced craniofacial defects. In contrast, the RRAS2 c.224T>G (p.Phe75Cys) change, located on the same allele with p.Gln72His in an individual with NS, resulted in no aberrant in vitro or in vivo phenotypes by itself. Together, our findings suggest that activating RRAS2 mutations can cause NS and expand the involvement of RRAS2 proto-oncogene to rare germline disorders.

Autosomal recessive Noonan syndrome associated with biallelic LZTR1 variants

PURPOSE

To characterize the molecular genetics of autosomal recessive Noonan syndrome.

METHODS

Families underwent phenotyping for features of Noonan syndrome in children and their parents. Two multiplex families underwent linkage analysis. Exome, genome, or multigene panel sequencing was used to identify variants. The molecular consequences of observed splice variants were evaluated by reverse-transcription polymerase chain reaction.

RESULTS

Twelve families with a total of 23 affected children with features of Noonan syndrome were evaluated. The phenotypic range included mildly affected patients, but it was lethal in some, with cardiac disease and leukemia. All of the parents were unaffected. Linkage analysis using a recessive model supported a candidate region in chromosome 22q11, which includes LZTR1, previously shown to harbor mutations in patients with Noonan syndrome inherited in a dominant pattern. Sequencing analyses of 21 live-born patients and a stillbirth identified biallelic pathogenic variants in LZTR1, including putative loss-of-function, missense, and canonical and noncanonical splicing variants in the affected children, with heterozygous, clinically unaffected parents and heterozygous or normal genotypes in unaffected siblings.

CONCLUSION

These clinical and genetic data confirm the existence of a form of Noonan syndrome that is inherited in an autosomal recessive pattern and identify biallelic mutations in LZTR1.

RAS-pathway mutation patterns define epigenetic subclasses in juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative disorder of early childhood characterized by mutations activating RAS signaling. Established clinical and genetic markers fail to fully recapitulate the clinical and biological heterogeneity of this disease. Here we report DNA methylome analysis and mutation profiling of 167 JMML samples. We identify three JMML subgroups with unique molecular and clinical characteristics. The high methylation group (HM) is characterized by somatic PTPN11 mutations and poor clinical outcome. The low methylation group is enriched for somatic NRAS and CBL mutations, as well as for Noonan patients, and has a good prognosis. The intermediate methylation group (IM) shows enrichment for monosomy 7 and somatic KRAS mutations. Hypermethylation is associated with repressed chromatin, genes regulated by RAS signaling, frequent co-occurrence of RAS pathway mutations and upregulation of DNMT1 and DNMT3B, suggesting a link between activation of the DNA methylation machinery and mutational patterns in JMML.

Is Neurofibromatosis Type 1-Noonan Syndrome a Phenotypic Result of Combined Genetic and Epigenetic Factors?

BACKGROUND/AIM

Neurofibromatosis 1-Noonan syndrome (NFNS) presents combined characteristics of both autosomal dominant disorders: NF1 and Noonan syndrome (NS). The genes causing NF1 and NS are located on different chromosomes, making it uncertain whether NFNS is a separate entity as previously suggested, or rather a clinical variation.

PATIENTS AND METHODS

We present a four-membered Greek family. The father was diagnosed with familial NF1 and the mother with generalized epilepsy, being under hydantoin treatment since the age of 18 years. Their two male children exhibited NFNS characteristics.

RESULTS

The father and his sons shared R1947X mutation in the NF1 gene. The two children with NFNS phenotype presented with NF1 signs inherited from their father and fetal hydantoin syndrome-like phenotype due to exposure to that anticonvulsant during fetal development.

CONCLUSION

The NFNS phenotype may be the result of both a genetic factor (mutation in the NF1 gene) and an epigenetic/environmental factor (e.g. hydantoin).

Growth patterns of patients with Noonan syndrome: correlation with age and genotype

BACKGROUND

Growth patterns of patients with Noonan syndrome (NS) were established before the involved genes were identified.

OBJECTIVE

The goal of this study was to compare growth parameters according to genotype in patients with NS.

SUBJECTS AND METHODS

The study population included 420 patients (176 females and 244 males) harboring mutations in the PTPN11, SOS1, RAF1, or KRAS genes. NS-associated PTPN11 mutations (NS-PTPN11) and NS with multiple lentigines-associated PTPN11 mutations (NSML-PTPN11) were distinguished. Birth measures and height and body mass index (BMI) measures at 2, 5, 10 years, and adulthood were compared with the general population and between genotypes.

RESULTS

Patients with NS were shorter at birth (mean birth length standard deviation score (SDS): -1.0 ± 1.4; P < 0.001) and throughout childhood than the healthy population, with height SDS being -2.1 ± 1.3 at 2 years, and -2.1 ± 1.2 at 5 and 10 years and adulthood (P < 0.001). At birth, patients with NS-PTPN11 were significantly shorter and thinner than patients with NSML-PTPN11, SOS1, or KRAS. Growth retardation was significantly less severe and less frequent at 2 years in patients with NSML-PTPN11 and SOS1 than in patients with NS-PTPN11 (P < 0.001 and P = 0.002 respectively). Patients with NS had lower BMI at 10 years (P < 0.001). No difference between genotypes was demonstrated.

CONCLUSION

Determining the growth patterns of patients with NS according to genotype should better inform clinicians about the natural course of growth in NS so that they can optimize the follow-up and management of these patients.

[Noonan syndrome can be diagnosed clinically and through molecular genetic analyses]

Noonan syndrome is part of the group of RASopathies caused by germ line mutations in genes involved in the RAS/MAPK pathway. There is substantial phenotypic overlap among the RASopathies. Diagnosis of Noonan syndrome is often based on clinical features including dysmorphic facial features, short stature and congenital heart disease. Rapid advances in sequencing technology have made molecular genetic analyses a helpful tool in diagnosing and distinguishing Noonan syndrome from other RASopathies.

Bone status in genetic syndromes: a review

More and more data seem to indicate the presence of an increasing number of syndromes and genetic diseases characterized by impaired bone mass and quality. Meanwhile, the improvement of etiopathogenetic knowledge and the employment of more adequate treatments have generated a significant increase in survival related to these syndromes and diseases. It is thus important to identify and treat bone impairment in these patients in order to assure a better quality of life. This review provides an updated overview of bone pathophysiology and characteristics in patients with Down, Turner, Klinefelter, Marfan, Williams, Prader-Willi, Noonan, and 22q11 deletions syndrome. In addition, some options for the treatment of the bone status impairment in these patients will be briefly discussed.

Oral manifestations of Noonan syndrome: review of the literature and a report of four cases

Noonan syndrome (NS) was described by Noonan and Ehmke as a multi-system disorder, which is typically evident at birth. The incidence of this syndrome is estimated to be one per 2500 to one per 1000 and affects both genders. While the clinical manifestations of NS have been well documented, the oral manifestations have not been extensively discussed. The purpose of the present article is to (a) review the oral manifestations of NS reported in the literature, and (b) describe four cases (three females and one male) of NS, who presented with short stature, cardiac problems and various oral findings. Based on these cases, we conclude that many oral anomalies may have possible relationships with NS, which require multidisciplinary treatment planning and timely management. The importance of oral findings in NS has largely gone unnoticed and it is essential to consider oral manifestations as scoring criteria in the diagnosis of NS.

Gain-of-function mutations in RIT1 cause Noonan syndrome, a RAS/MAPK pathway syndrome

RAS GTPases mediate a wide variety of cellular functions, including cell proliferation, survival, and differentiation. Recent studies have revealed that germline mutations and mosaicism for classical RAS mutations, including those in HRAS, KRAS, and NRAS, cause a wide spectrum of genetic disorders. These include Noonan syndrome and related disorders (RAS/mitogen-activated protein kinase [RAS/MAPK] pathway syndromes, or RASopathies), nevus sebaceous, and Schimmelpenning syndrome. In the present study, we identified a total of nine missense, nonsynonymous mutations in RIT1, encoding a member of the RAS subfamily, in 17 of 180 individuals (9%) with Noonan syndrome or a related condition but with no detectable mutations in known Noonan-related genes. Clinical manifestations in the RIT1-mutation-positive individuals are consistent with those of Noonan syndrome, which is characterized by distinctive facial features, short stature, and congenital heart defects. Seventy percent of mutation-positive individuals presented with hypertrophic cardiomyopathy; this frequency is high relative to the overall 20% incidence in individuals with Noonan syndrome. Luciferase assays in NIH 3T3 cells showed that five RIT1 alterations identified in children with Noonan syndrome enhanced ELK1 transactivation. The introduction of mRNAs of mutant RIT1 into 1-cell-stage zebrafish embryos was found to result in a significant increase of embryos with craniofacial abnormalities, incomplete looping, a hypoplastic chamber in the heart, and an elongated yolk sac. These results demonstrate that gain-of-function mutations in RIT1 cause Noonan syndrome and show a similar biological effect to mutations in other RASopathy-related genes.

Increased rate of missense/in-frame mutations in individuals with NF1-related pulmonary stenosis: a novel genotype-phenotype correlation

Neurofibromatosis type 1 (NF1) and its related disorders (NF1-Noonan syndrome (NFNS) and Watson syndrome (WS)) are caused by heterozygous mutations in the NF1 gene. Pulmonary stenosis (PS) occurs more commonly in NF1 and its related disorders than in the general population. This study investigated whether PS is associated with specific types of NF1 gene mutations in NF1, NFNS and WS. The frequency of different NF1 mutation types in a cohort of published and unpublished cases with NF1/NFNS/WS and PS was examined. Compared with NF1 in general, NFNS patients had higher rates of PS (9/35=26% vs 25/2322=1.1%, P value<0.001). Stratification according to mutation type showed that the increased PS rate appears to be driven by the NFNS group with non-truncating mutations. Eight of twelve (66.7%) NFNS cases with non-truncating mutations had PS compared with a 1.1% PS frequency in NF1 in general (P<0.001); there was no increase in the frequency of PS in NFNS patients with truncating mutations. Eight out of eleven (73%) individuals with NF1 and PS, were found to have non-truncating mutations, a much higher frequency than the 19% reported in NF1 cohorts (P<0.015). Only three cases of WS have been published with intragenic mutations, two of three had non-truncating mutations. Therefore, PS in NF1 and its related disorders is clearly associated with non-truncating mutations in the NF1 gene providing a new genotype-phenotype correlation. The data indicate a specific role of non-truncating mutations on the NF1 cardiac phenotype.

Tegumentary manifestations of Noonan and Noonan-related syndromes

OBJECTIVES

Noonan and Noonan-related syndromes are common autosomal dominant disorders with neuro-cardio-facial-cutaneous and developmental involvement. The objective of this article is to describe the most relevant tegumentary findings in a cohort of 41 patients with Noonan or Noonan-related syndromes and to detail certain aspects of the molecular mechanisms underlying ectodermal involvement.

METHODS

A standard questionnaire was administered. A focused physical examination and a systematic review of clinical records was performed on all patients to verify the presence of tegumentary alterations. The molecular analysis of this cohort included sequencing of the following genes in all patients: PTPN1, SOS1, RAF1, KRAS, SHOC2 and BRAF.

RESULTS

The most frequent tegumentary alterations were xeroderma (46%), photosensitivity (29%), excessive hair loss (24%), recurrent oral ulcers (22%), curly hair (20%), nevi (17%), markedly increased palmar and plantar creases (12%), follicular hyperkeratosis (12%), palmoplantar hyperkeratosis (10%), café-au-lait spots (10%) and sparse eyebrows (7%). Patients with mutations in PTPN11 had lower frequencies of palmar and plantar creases and palmar/plantar hyperkeratosis compared with the other patients.

CONCLUSIONS

We observed that patients with mutations in genes directly involved in cell proliferation kinase cascades (SOS1, BRAF, KRAS and RAF1) had a higher frequency of hyperkeratotic lesions compared with patients with mutations in genes that have a more complex interaction with and modulation of cell proliferation kinase cascades (PTPN11).

Neurofibromatosis-Noonan syndrome: case report and clinicopathogenic review of the Neurofibromatosis-Noonan syndrome and RAS-MAPK pathway

Neurofibromatosis-Noonan syndrome is an entity that combines both features of Noonan syndrome and Neurofibromatosis type 1. This phenotypic overlap can be explained by the involvement of the RAS-MAPK pathway (mitogen-activated protein kinase) in both disorders. We report the case of a 17-year-old boy with Neurofibromatosis 1 with Noonan-like features, who complained of the progressive appearance of blue-gray lesions on his back.

The RASopathies: developmental syndromes of Ras/MAPK pathway dysregulation

The Ras/mitogen activated protein kinase (MAPK) pathway is essential in the regulation of the cell cycle, differentiation, growth and cell senescence, all of which are critical to normal development. It is therefore not surprising that its dysregulation has profound effects on development. A class of developmental syndromes, the 'RASopathies', is caused by germline mutations in genes that encode protein components of the Ras/MAPK pathway. The vast majority of these mutations result in increased signal transduction down the Ras/MAPK pathway, but usually to a lesser extent than somatic mutations associated with oncogenesis. Each syndrome exhibits unique phenotypic features, however, since they all cause dysregulation of the Ras/MAPK pathway, there are numerous overlapping phenotypic features between the syndromes, including characteristic facial features, cardiac defects, cutaneous abnormalities, neurocognitive delay and a predisposition to malignancies. Here we review the clinical and underlying molecular basis for each of these syndromes.

Germline BRAF mutations in Noonan, LEOPARD, and cardiofaciocutaneous syndromes: molecular diversity and associated phenotypic spectrum

Noonan, LEOPARD, and cardiofaciocutaneous syndromes (NS, LS, and CFCS) are developmental disorders with overlapping features including distinctive facial dysmorphia, reduced growth, cardiac defects, skeletal and ectodermal anomalies, and variable cognitive deficits. Dysregulated RAS-mitogen-activated protein kinase (MAPK) signal traffic has been established to represent the molecular pathogenic cause underlying these conditions. To investigate the phenotypic spectrum and molecular diversity of germline mutations affecting BRAF, which encodes a serine/threonine kinase functioning as a RAS effector frequently mutated in CFCS, subjects with a diagnosis of NS (N=270), LS (N=6), and CFCS (N=33), and no mutation in PTPN11, SOS1, KRAS, RAF1, MEK1, or MEK2, were screened for the entire coding sequence of the gene. Besides the expected high prevalence of mutations observed among CFCS patients (52%), a de novo heterozygous missense change was identified in one subject with LS (17%) and five individuals with NS (1.9%). Mutations mapped to multiple protein domains and largely did not overlap with cancer-associated defects. NS-causing mutations had not been documented in CFCS, suggesting that the phenotypes arising from germline BRAF defects might be allele specific. Selected mutant BRAF proteins promoted variable gain of function of the kinase, but appeared less activating compared to the recurrent cancer-associated p.Val600Glu mutant. Our findings provide evidence for a wide phenotypic diversity associated with mutations affecting BRAF, and occurrence of a clinical continuum associated with these molecular lesions.

Impaired Sertoli cell function in males diagnosed with Noonan syndrome

In order to study male gonadal function in Noonan syndrome, clinical and laboratory data, including inhibin B, were gathered in nine pubertal males diagnosed with Noonan syndrome. Bilateral testicular maldescent was observed in four, and unilateral cryptorchidism occurred in two. Puberty was delayed in three patients. Luteinising hormone (LH) levels were normal in all patients in our series, while follicle stimulating hormone (FSH) levels were raised in seven. Inhibin B was low in six males and just above the lower limit of normal in two. Importantly, all three men with normal testicular descent displayed signs of Sertoli cell dysfunction, indicating, in contrast to earlier reports, that bilateral cryptorchidism does not seem to be the main contributing factor to impairment of testicular function in Noonan syndrome. These findings suggest different mechanisms of disturbance in male gonadal function, which is frequently associated with Sertoli dysfunction.

Mediating ERK 1/2 signaling rescues congenital heart defects in a mouse model of Noonan syndrome

Noonan syndrome (NS) is an autosomal dominant disorder characterized by a wide spectrum of defects, which most frequently include proportionate short stature, craniofacial anomalies, and congenital heart disease (CHD). NS is the most common nonchromosomal cause of CHD, and 80%-90% of NS patients have cardiac involvement. Mutations within the protein tyrosine phosphatase Src homology region 2, phosphatase 2 (SHP2) are responsible for approximately 50% of the cases of NS with cardiac involvement. To understand the developmental stage- and cell type-specific consequences of the NS SHP2 gain-of-function mutation, Q79R, we generated transgenic mice in which the mutated protein was expressed during gestation or following birth in cardiomyocytes. Q79R SHP2 embryonic hearts showed altered cardiomyocyte cell cycling, ventricular noncompaction, and ventricular septal defects, while, in the postnatal cardiomyocyte, Q79R SHP2 expression was completely benign. Fetal expression of Q79R led to the specific activation of the ERK1/2 pathway, and breeding of the Q79R transgenics into ERK1/2-null backgrounds confirmed the pathway's necessity and sufficiency in mediating mutant SHP2's effects. Our data establish the developmental stage-specific effects of Q79R cardiac expression in NS; show that ablation of subsequent ERK1/2 activation prevents the development of cardiac abnormalities; and suggest that ERK1/2 modulation could have important implications for developing therapeutic strategies in CHD.

Cardio-facio-cutaneous and Noonan syndromes due to mutations in the RAS/MAPK signalling pathway: genotype-phenotype relationships and overlap with Costello syndrome

Cardio-facio-cutaneous (CFC) syndrome, Noonan syndrome (NS), and Costello syndrome (CS) are clinically related developmental disorders that have been recently linked to mutations in the RAS/MEK/ERK signalling pathway. This study was a mutation analysis of the KRAS, BRAF, MEK1 and MEK2 genes in a total of 130 patients (40 patients with a clinical diagnosis of CFC, 20 patients without HRAS mutations from the French Costello family support group, and 70 patients with NS without PTPN11 or SOS1 mutations). BRAF mutations were found in 14/40 (35%) patients with CFC and 8/20 (40%) HRAS-negative patients with CS. KRAS mutations were found in 1/40 (2.5%) patients with CFC, 2/20 (10%) HRAS-negative patients with CS and 4/70 patients with NS (5.7%). MEK1 mutations were found in 4/40 patients with CFC (10%), 4/20 (20%) HRAS-negative patients with CS and 3/70 (4.3%) patients with NS, and MEK2 mutations in 4/40 (10%) patients with CFC. Analysis of the major phenotypic features suggests significant clinical overlap between CS and CFC. The phenotype associated with MEK mutations seems less severe, and is compatible with normal mental development. Features considered distinctive for CS were also found to be associated with BRAF or MEK mutations. Because of its particular cancer risk, the term "Costello syndrome" should only be used for patients with proven HRAS mutation. These results confirm that KRAS is a minor contributor to NS and show that MEK is involved in some cases of NS, demonstrating a phenotypic continuum between the clinical entities. Although some associated features appear to be characteristic of a specific gene, no simple rule exists to distinguish NS from CFC easily.

Respiratory failure, juvenile myelomonocytic leukemia, and neonatal Noonan syndrome

Noonan syndrome (NS) is a multiple malformation syndrome where confirmation of diagnosis is difficult in the newborn. We report a case of a dysmorphic neonate who presented with bilateral chylous effusions and juvenile myelomonocytic leukemia where NS was confirmed by the presence of PTPN11 mutation. Juvenile myelomonocytic leukemia in NS is uncommon. The leukemia is usually self-limiting but lethal cases have been reported. Decisions regarding need for the treatment are unclear and further understanding of the genotype-phenotype relationships in PTPN11 mutations may help direct this.

Persistence of Nuchal Edema and Distended Jugular Lymphatic Sacs in Noonan Syndrome

OBJECTIVE

Noonan syndrome is one of the most common genetic syndromes manifesting at birth. Still, it is diagnosed late, often during infancy. Diagnosis is difficult because prenatal ultrasound findings are unspecific and the dysmorphias after birth can be subtle.

CASES

Two women were referred to our university hospital because of an increased nuchal translucency in the first trimester of pregnancy. Further ultrasound examination showed the bilateral presence of distended jugular lymph sacs. Karyotyping revealed euploidy in both fetuses. The second trimester ultrasound scan showed a persistence of the jugular lymph sacs together with a nuchal fold, indicating a disturbed lymphatic development. There were no other anomalies. In 1 case the jugular lymph sacs containing newly formed lymph node tissue remained visible until 35 weeks' gestation. Both newborns were diagnosed with Noonan syndrome after birth. Postnatal echocardiography revealed a mild pulmonary stenosis.

CONCLUSION

Distension of the jugular lymph sacs is known to cause nuchal edema and normally resolves after the first trimester. In case of persistence of the jugular lymphatic sacs beyond the second trimester of pregnancy, the diagnosis of Noonan syndrome and subsequent DNA testing should be considered.

Pregnancy following oocyte donation in a woman with Noonan's syndrome and a balanced Robertsonian translocation a case report

Successful pregnancy in Noonan's syndrome and balanced Robertsonian translocation women is extremely rare. This is because pregnancies in these women usually end in spontaneous miscarriage or termination before 24 weeks gestation due to severe congenital anomaly. In this article, we report the case of a 41-years-old woman with Noonan's syndrome and balanced Robertsonian translocation. She was delivered by an elective caesarean section at 38 weeks of a live male infant following a second attempt of in vitro fertilisation (IVF) and embryo transfer from donor oocytes. The use of donor eggs and IVF in these women means more of them will achieve successful term pregnancy as in this case. It is therefore important that Obstetricians understand this rare condition and optimise care. This case highlights some of the medical problems encountered by Obstetricians in managing patients in this high risk group.

Mild variable Noonan syndrome in a family with a novel PTPN11 mutation

Noonan syndrome (OMIM 163950) is a common genetic condition with variable clinical expression and genetic heterogeneity. About half of the cases can be accounted to activating mutations in the PTPN11 gene encoding SHP-2. We report on a family with mild, variable expression of Noonan syndrome in five individuals. Clinical manifestations included short stature, craniofacial anomalies and thorax deformity, but none of the affected family members had a heart defect. Sequencing of the entire coding region of PTPN11 revealed a novel mutation c.1226G-->C in exon 11 predicting the amino acid exchange G409A. This mutation is not located in the previously known mutation clusters. Our observation and the recent report of a mutation affecting a neighbouring residue (T411M) in a family with a variable phenotype suggest that mutations in this particular region of SHP-2 may have effects on the protein that differ from those of the classical mutations.

Noonan syndrome: relationships between genotype, growth, and growth factors

CONTEXT

Half of the patients with Noonan syndrome (NS) carry mutation of the PTPN11 gene, which plays a role in many hormonal signaling pathways. The mechanism of stunted growth in NS is not clear.

OBJECTIVE

The objective of the study was to compare growth and hormonal growth factors before and during recombinant human GH therapy in patients with and without PTPN11 mutations (M+ and M-).

SETTING, DESIGN, AND PATIENTS

This was a prospective multicenter study in 35 NS patients with growth retardation. Auxological data and growth before and during 2 yr of GH therapy are shown. GH, IGF-I, IGF binding protein (IGFBP)-3, and acid-labile subunit (ALS) levels were evaluated before and during therapy.

RESULTS

Molecular investigation of the PTPN11 coding sequence revealed 12 different heterozygous missense mutations in 20 of 35 (57%). Birth length was reduced [mean -1.2 sd score (SDS); six m+ and two m- were < -2 SDS] but not birth weight. M+ vs. M- patients were shorter at 6 yr (P = 0.04). In the prepubertal group (n = 25), GH therapy resulted in a catch-up height SDS, which was lower after 2 yr in M+ vs. M- patients (P < 0.03). The mean peak GH level (n = 35) was 15.4 +/- 6.5 ng/ml. Mean blood IGF-I concentration in 19 patients (11 m+, eight m-) was low (especially in M+) for age, sex, and puberty (-1.6 +/- 1.0 SDS) and was normalized after 1 yr of GH therapy (P < 0.001), without difference in M+ vs. M- patients. ALS levels (n = 10) were also very low. By contrast, the mean basal IGFBP-3 value (n = 19) was normal.

CONCLUSIONS

In NS patients with short stature, some neonates have birth length less than -2 SDS. Growth of M+ is reduced and responds less efficiently to GH than M- patients. The association of low IGF-I and ALS with normal IGFBP-3 levels could explain growth impairment of M+ children and could suggest a GH resistance by a late postreceptor signaling defect.

Prenatal DNA diagnosis of Noonan syndrome in a fetus with massive hygroma colli, pleural effusion and ascites

Prenatal molecular genetic diagnosis for Noonan syndrome I is reported. Noonan syndrome was suspected because of large cystic hygroma colli, massive pleural effusion and ascites at 23 weeks of gestation and normal karyotype (46,XX). DNA was prepared from amnion cells and screened for mutations in the PTPN11 gene. In exon 8, a missense mutation (S285F) was found. Delivery was induced at 33 weeks of gestation because of silent cardiotocography (CTG). Despite immediate drainage of the hydrothorax, mechanical ventilation was insufficient and the child died 9 h after birth due to severe pulmonary hypoplasia. Pleural punctate was enriched for small lymphocytes and thus was characterized as chylus. Prenatal ultrasound findings in Noonan syndrome usually are unspecific and rarely lead to a diagnosis. However, with the combination of cystic hygroma, pleural effusion, ascites and normal karyotype Noonan syndrome should be considered and DNA testing for PTPN11 mutations may be appropriate. Malformations of lymphatic vessels and/or chylothorax in Noonan syndrome seem to be more frequent than usually anticipated.

NF1 gene mutations represent the major molecular event underlying neurofibromatosis-Noonan syndrome

Neurofibromatosis type 1 (NF1) demonstrates phenotypic overlap with Noonan syndrome (NS) in some patients, which results in the so-called neurofibromatosis-Noonan syndrome (NFNS). From a genetic point of view, NFNS is a poorly understood condition, and controversy remains as to whether it represents a variable manifestation of either NF1 or NS or is a distinct clinical entity. To answer this question, we screened a cohort with clinically well-characterized NFNS for mutations in the entire coding sequence of the NF1 and PTPN11 genes. Heterozygous NF1 defects were identified in 16 of the 17 unrelated subjects included in the study, which provides evidence that mutations in NF1 represent the major molecular event underlying this condition. Lesions included nonsense mutations, out-of-frame deletions, missense changes, small inframe deletions, and one large multiexon deletion. Remarkably, a high prevalence of inframe defects affecting exons 24 and 25, which encode a portion of the GAP-related domain of the protein, was observed. On the other hand, no defect in PTPN11 was observed, and no lesion affecting exons 11-27 of the NF1 gene was identified in 100 PTPN11 mutation-negative subjects with NS, which provides further evidence that NFNS and NS are genetically distinct disorders. These results support the view that NFNS represents a variant of NF1 and is caused by mutations of the NF1 gene, some of which have been demonstrated to cause classic NF1 in other individuals.

Discriminating power of localized three-dimensional facial morphology

Many genetic syndromes involve a facial gestalt that suggests a preliminary diagnosis to an experienced clinical geneticist even before a clinical examination and genotyping are undertaken. Previously, using visualization and pattern recognition, we showed that dense surface models (DSMs) of full face shape characterize facial dysmorphology in Noonan and in 22q11 deletion syndromes. In this much larger study of 696 individuals, we extend the use of DSMs of the full face to establish accurate discrimination between controls and individuals with Williams, Smith-Magenis, 22q11 deletion, or Noonan syndromes and between individuals with different syndromes in these groups. However, the full power of the DSM approach is demonstrated by the comparable discriminating abilities of localized facial features, such as periorbital, perinasal, and perioral patches, and the correlation of DSM-based predictions and molecular findings. This study demonstrates the potential of face shape models to assist clinical training through visualization, to support clinical diagnosis of affected individuals through pattern recognition, and to enable the objective comparison of individuals sharing other phenotypic or genotypic properties.

Juvenile papillomatosis of the breast in a male infant with Noonan syndrome, café au lait spots, and family history of breast carcinoma

Juvenile papillomatosis (JP) of the breast is a rare condition, usually affecting women under 30 years of age. Although this is considered a benign lesion, follow-up is recommended for the patient and family since there is an association with a family history of breast carcinoma and increased risk of development of breast carcinoma. We report an infant with JP, Noonan syndrome (NS), café au lait spots, and family history of breast carcinoma. Seven previously reported cases of JP in males exist, two occurring in infants. The association between JP and NS has not been previously reported.

PTPN11 (protein tyrosine phosphatase, nonreceptor type 11) mutations and response to growth hormone therapy in children with Noonan syndrome

CONTEXT

The cause of growth impairment in Noonan syndrome (NS) remains unclear. Mutations in PTPN11 (protein tyrosine phosphatase, nonreceptor type 11) that codify constitutively activated Src homology protein tyrosine phosphatase-2 tyrosine phosphatase and may interfere with GH and IGF-I signaling were identified in approximately 40% of patients with NS.

OBJECTIVE

The objective of this study was to evaluate the influence of PTPN11 status on response to human GH (hGH) treatment in NS children with short stature.

SETTING

This study was performed at a university hospital.

DESIGN

The study design was to conduct a retrospective analysis of 3 yr of hGH treatment and genotyping of PTPN11 in patients with NS.

PATIENTS

Fourteen NS patients, half of them with PTPN11 mutations in heterozygous state, were studied. At the beginning of treatment, there were no clinical or laboratory differences between groups with and without mutations in the PTPN11 gene.

INTERVENTION

Patients were treated with hGH (47 microg/kg.d).

MAIN OUTCOME MEASURES

The main outcome measures were PTPN11 genotype, change in IGF-I levels, and change in height sd score.

RESULTS

Patients with mutations in PTPN11 presented a significantly smaller increment in IGF-I levels during the treatment compared with patients without mutations (86 +/- 67 and 202 +/- 93 microg/liter, respectively; P = 0.03). hGH treatment significantly improved growth velocity in both groups, with slightly better results observed in patients without mutations. This was translated into greater gains in height sd score relation to baseline during the 3 yr of treatment in patients without mutations (+1.7 +/- 0.1) compared with those with mutations (+0.8 +/- 0.4; P < 0.01).

CONCLUSIONS

Our findings suggest that the presence of PTPN11 mutations in patients with NS indicates a reduced growth response to long-term hGH treatment.