1. Introduction
Noonan syndrome (NS) is a genetic disorder with a prevalence ranging from 1 in 1000 to 1 in 2500 live births. It is characterized by short stature, distinctive facial and skeletal dysmorphisms (e.g., hypertelorism), down-slanting palpebral fissures, high arched palate, low set posteriorly rotated ears, ptosis, pectus excavatum or carinatum, scoliosis, mild to moderate developmental delay, and a heterogeneous pattern of abnormalities involving the cardiovascular, musculoskeletal, and endocrine systems [1,2,3].
NS belongs to the RASopathies, a group of conditions with overlapping features including cardio-facio-cutaneous syndrome, Costello syndrome, LEOPARD syndrome, Mazzanti syndrome, Legius syndrome, Neurofibromatosis–Noonan syndrome, and an increasing number of related disorders [4]. Germline mutations in genes encoding for components of the RAS/MAPK (mitogen-activated protein kinase) signaling pathway are responsible for RASopathies. This pathway is involved in cell growth, differentiation, proliferation, migration, and apoptosis [5,6,7]. The first gene associated with NS, responsible for 50% of cases, is the Protein-tyrosine phosphatase, nonreceptor-type 11 (PTPN11), which encodes the Src homology-containing protein tyrosine phosphatase 2 (SHP2) involved in several intracellular signals [8].
Several functionally related genes, such as SOS1, RAF1, RIT1, KRAS, NRAS, BRAF, SOS2, SHOC2, LZTR1, and others, have been associated with the pathogenesis of NS; thus, the causal mutations remain unidentified in about 10–20% of patients [9,10].
This genetic heterogeneity reflects the complexity of NS, which has various clinical manifestations that can differ widely between affected individuals.
Mutations associated with NS, particularly in the PTPN11 gene, have a direct impact on bone development and contribute to abnormal bone growth [11]. Short stature is one of the main features of NS. Growth retardation usually occurs during the first year of life and becomes increasingly evident due to delayed puberty and the reduction in the pubertal growth spurt [12]. A decrease in bone mass, which correlates with decreased muscle mass and low IGF-1 serum levels, has been observed in children with NS [13]. An alteration of bone quality assessed using phalangeal quantitative ultrasound (QUS), in the absence of fracture risk, has also been reported in NS children [14]. In addition, reduced physical activity, hypotonia, reduced sun exposure, and low 25-OH vitamin D serum levels can increase the risk of osteopenia or osteoporosis in subjects with RASopathies.
In adult NS patients, a progression towards marked demineralization and vertebral fractures has been observed, despite treatment with bisphosphonates, teriparatide, and denosumab [15].
However, the effects of RAS/MAPK pathway dysregulation on bone health in subjects affected with NS and other RASopathies remain insufficiently explored, although alterations in bone matrix, osteopenia, and osteoporosis have been documented [11,13,16]. In addition, data on bone turnover markers in this group of diseases are few and conflicting [11,13,14].
Bone tissue is characterized by continuous remodeling in which resorption is followed by formation. The cells that regulate bone remodeling are the osteoclasts, responsible for the resorption of the bone matrix, and the osteoblasts, responsible for the synthesis of the matrix components. Bone turnover markers reflect bone cell activity. In particular, bone alkaline phosphatase (BALP), osteocalcin (OC), and procollagen I N-propeptide (P1NP) reflect the osteoblast activity, while the production of fragments of the degradation of type I collagen (N- and C-telopeptides of type I collagen- NTX and CTX) reflects osteoclast activity [17,18].
In addition, the balance of bone remodeling is regulated mainly by the nuclear factor kappa-B ligand (RANKL)/RANK/osteoprotegerin (OPG) and Wnt/β-catenin pathways, which control osteoclastogenesis and osteoblastogenesis, respectively [19,20]. Furthermore, the pro-osteoblastogenic activity of the Wnt/β-catenin pathway can be inhibited by sclerostin and Dickkopf-1 (DKK-1). Altered bone remodeling has been shown to cause bone impairment in many congenital and acquired pediatric diseases [21].
This study aimed to evaluate bone turnover and bone remodeling markers in a cohort of children with NS by assessing the serum levels of BALP, OC, P1NP, CTX, RANKL, OPG, and sclerostin to gain insights into the bone status of these patients.
In addition, we sought a possible correlation between the type of genetic mutation and bone remodeling status in these patients to identify those at risk of osteoporosis early in life.
2. Materials and Methods
The study group included 28 children (20 males) with a molecular diagnosis of NS, mean age at recruitment of 10.5 ± 6.07. years, who were followed at the Endocrinology and Rare Endocrine Diseases Clinic of the University of Bari, Italy.
The control group comprised 35 healthy subjects (21 males), pair matched by age (8.6 ± 4.9), attending our Pediatric Clinic for minor trauma (first aid) or allergology screening. None of them had received a bone injury. The study’s exclusion criteria for both patients and controls were the chronic use of drugs that interfere with bone metabolism (steroids, proton pump inhibitors, antiepileptics) and any immune diseases.
The study protocol was approved by the Local Ethics Committee. The children’s parents or guardians provided written informed consent. All procedures were carried out in accordance with the guidelines of the Helsinki Declaration on Human Experimentation.
2.1. Clinical Data
Clinical features of the NS patients, including age, sex, type of gene mutation, and information about recombinant human GH (rhGH) treatment (in progress, suspended, or never started), were collected. Anthropometric parameters, including height (H) with Harpenden stadiometer and weight (W), were assessed for every patient and were compared with the standard growth charts for the Italian population, and were expressed as a standard deviation score (SDS) [22]. Body mass index (BMI) was calculated as the ratio of weight/height2. Pubertal stages were assessed using the Tanner method [23].
2.2. Biochemical Assessments of Bone Metabolism Markers
After an overnight fast, venous peripheral blood samples were collected from patients and controls. The samples were promptly centrifuged and immediately frozen at −80 °C until analysis.
Calcium and phosphate levels were measured using the spectrophotometric method. Parathyroid hormone (PTH) and 25-OH vitamin D were assessed using immunological tests based on the principle of chemiluminescence (Liaison assay; DiaSorin, Stillwater, MN, USA).
Serum OC was assessed using an enzyme immunoassay (Immunodiagnostic Systems Ltd., 10 Didct Way, Boldon Business Park, Boldon, Tyne and Wear, UK, NE35 9PD) with an analytical sensitivity of 2 ng/mL and a linear range of 2–200 ng/mL. Serum P1NP was measured using an enzyme immunoassay (Immunodiagnostic Systems Ltd., 10 Didct Way, Boldon Business Park, Boldon, Tyne and Wear, UK, NE35 9PD) with an analytical sensitivity of 2 ng/mL and a linear range of 2–230 ng/mL. BALP was measured using an enzyme immunoassay (Immunodiagnostic Systems Ltd., 10 Didct Way, Boldon Business Park, Boldon, Tyne and Wear, UK, NE35 9PD) with an analytical sensitivity of 1 μg/L and a linear range of 1–75 μg/L. CTX was measured using an enzyme immunoassay (Immunodiagnostic Systems Ltd., 10 Didct Way, Boldon Business Park, Boldon, Tyne and Wear, UK, NE35 9PD) with an analytical sensitivity of 0.033 ng/mL and a linear range of 0.033–6000 ng/mL.
2.3. Bone Remodeling Cytokines Assessment
Sclerostin, RANKL, and OPG were assessed using ELISA (R&D Systems, Minneapolis, MN, USA; Biomedica Medizinprodukte, GmbH & Co KG, Vienna, Austria). The specific characteristics of each ELISA kit are as follows: sclerostin: assay range 0–240 pmol/L with intra-assay CV ≤ 7% and inter-assay CV ≤ 10%; RANKL: assay range 0–2 pmol/L with intra-assay CV ≤ 4% and inter-assay CV ≤ 3%; OPG: assay range 0–20 pmol/L with intra-assay CV ≤ 3% and inter-assay CV ≤ 5%.
Table 1 summarizes the role of the bone turnover markers analyzed in this study.
2.4. Bone Mineral Measurements
Bone mineralization was measured at the lumbar spine (L2–L4) using the dual-energy X-ray absorptiometry (DEXA) equipment at our center (ACN Unigamma X-ray Plus; L’ACN Scientific Laboratories; Hologic DiscoveryWi; Lunar iDXA, GE Healthcare) and was converted to Z-scores in relation to an age- and sex-matched normal population.
2.5. Statistical Analysis
Results are reported as means ± standard deviation. The Kolmogorov–Smirnov test was used to determine the normality of the parameters’ distribution. In parameters with a normal distribution, mean values were compared using the unpaired Student t-test, whereas linear correlations were evaluated using the Pearson correlation coefficient. The significance of parameters with a skewed distribution was assessed using the Mann–Whitney test and Spearman correlation coefficient. Variables with a non-normal distribution were expressed as medians and interquartile ranges (IQRs) and were compared using the Kruskal–Wallis test. The Statistical Package for the Social Sciences for Windows, version 27.0 (SPSS Inc., Chicago, IL, USA) was utilized for statistical analyses.
3. Results
3.1. Patients
Table 2 reports the clinical characteristics of the study population. Both groups were comparable in terms of age, sex distribution, BMI, and BMI-SDS. NS patients exhibited significantly lower height-SDS and weight-SDS compared to controls. Height and weight in absolute values were lower in NS patients, although the differences did not reach statistical significance. The mean bone age (BA) of NS subjects was 10.42 ± 4.7 years. No significant difference was observed in pubertal stage distribution between the two groups (Table 2).
The genetic characteristics of the NS population are shown in Figure 1.
Among them, 17 subjects (60.7%) harbored PTPN11 gene mutations, while 11 (39%) had the following gene mutations: 5 SOS1, 2 SHOC2, 1 KRAS, 1 LZTR1, 1 NRAS, and 1 RAF1—all cases were de novo mutations (Figure 1). Among the NS subjects, five had been treated with rhGH, reaching a mean final height of −3.72 ± 0.91 SDS, while two subjects were still receiving rhGH therapy at the time of recruitment. Congenital heart disease was present in 64.2% of NS subjects (14 pulmonary valve stenosis, three obstructive cardiomyopathies).
3.2. Bone Turnover and Bone Remodeling Markers
Table 3 shows the bone turnover and bone remodeling markers in the study population.
No difference was found between the two groups for serum levels of calcium, phosphate, PTH, OC, P1NP, or BALP. Mean values of 25-OH vitamin D in NS subjects were 26.7 ± 13.3 mg/mL; in particular, eight subjects had normal values (40.2 ± 11.1 ng/mL), 11 had insufficient values (24.5 ± 2.4 ng/mL), and nine were deficient (14.5 ± 4.6 ng/mL). NS patients had significantly higher serum CTX levels than controls (1.8 ± 0.7 vs. 1.3 ± 0.5 ng/mL, p = 0.0004). For bone remodeling cytokines, RANKL levels were higher in NS patients compared to controls, but this difference was not statistically significant. There were no significant differences in OPG and sclerostin levels between the two groups.
3.3. Bone Mineral Density Assessment
The cohort of subjects affected with NS exhibited a median bone mineral density Z-score (BMD Z score) at the lumbar spine (L1–L4) of −1.3. Specifically, 10 subjects had values below −2 Z-score (range: −4.3 to 0.79). Among these subjects, six had a PTPN11 mutation, two a SHOC2 mutation, one a KRAS mutation, and one a SOS1 mutation. Interestingly, the two subjects with a SHOC2 mutation had the most compromised BMD values (−4.3 and −2.6 Z-score, respectively). No subjects experienced fractures. A negative correlation was found between BMD Z-score and chronological age (r = −0.607; p = 0.002), whereas positive correlations were observed between BMD Z-score and phosphate levels (r = 0.005; p = 0.006), height SDS (r = 0.734; p < 0.001), BALP (r = 0.640; p = 0.001), and P1NP (r = 0.464; p = 0.034).
3.4. Bone Status According to the Genotype
To explore a possible genotype–phenotype correlation, we divided the NS cohort into two groups according to the presence or absence of PTPN11 gene mutations: (PTPN11+ and PTPN11-). No significant differences in age, pubertal stage, bone age, or anthropometric measures (height-SDS, weight-SDS, BMI-SDS) were observed between the two groups (Table 4). Additionally, bone turnover markers (OC, BALP, P1NP) showed no statistically significant differences between the two groups. CTX was slightly increased in PTPN11+ subjects, even if the difference was not statistically significant.
No difference in BMD-Z scores was found between rhGH-treated and untreated subjects. A significant difference was observed only in phosphate levels, with lower levels in GH-treated children (4.33 ± 0.5 mg/dL) compared to untreated children (4.80 ± 0.38 mg/dL, p = 0.02).
4. Discussion
Osteopenia and osteoporosis have been reported in NS and other RASopathies, suggesting a common pathogenesis [16]. Other comorbidities such as neurological impairment, intellectual disability, reduced physical activity, and hypotonia could affect bone health in NS subjects [24,25]. However, the mechanisms underlying reduced bone mineralization in the RASopathies are still poorly understood.
In this study, we assessed bone turnover and bone remodeling markers in a cohort of NS subjects, with the aim of investigating the bone status associated with this condition and correlating it to the genotype.
Our data demonstrated higher serum levels of CTX—a marker of bone resorption—than controls, in association with an increase in serum levels of RANKL—an osteoclastogenic cytokine—even if this increase did not reach statistical significance compared to controls. We found no differences between patients and controls with respect to sclerostin, an inhibitor of osteoblast activity, and bone metabolism parameters such as calcium, phosphate, PTH, and 25-OH vitamin D. Our data are in agreement with previous reports showing normal calcium, phosphate, PTH, 25-OH Vitamin D, and alkaline phosphatase (ALP) serum levels, and higher levels of carboxy-terminal collagen crosslinks in NS children compared to controls [11,13,14].
Markers of bone resorption identified using pyridinium crosslink analysis were also elevated in subjects affected with RASopathies compared to matched controls [26]. In our cohort of NS subjects, CTX levels were also slightly increased in PTPN11+ subjects, even if the difference was not statistically significant.
The RAS/MAPK regulates the cell cycle, differentiation, growth, and cell senescence. Specifically, SHP2 controls the ERK1/2 pathway and promotes the terminal differentiation of chondrocytes [27,28]. Inactivation of ERK1/2 in the growth plate causes chondrocytes to undergo hypertrophy prematurely and delays the replacement of cartilage with bone [29,30]. Additionally, it has been demonstrated that SHP2-deficient mice increase osteoclast activity, possibly due to increased RANKL expression in osteoblasts and chondrocytes [31].
Our data showed a reduction in BMD, particularly pronounced in subjects with SHOC2 gene mutations. These data align with Delagrange et al.’s finding of reduced axial and appendicular bone mass in a cohort of 35 NS children compared to the general population, as well as an increase in CTX serum levels [13].
Baldassarre et al. found reduced QUS measurements in 25% of NS cases, although bone metabolism markers were within the normal range [14]. Choudhry et al. documented a reduced BMD in 6 of 12 NS individuals, without any alterations in bone metabolism markers [11].
In our cohort of NS patients, we did not find a genotype–phenotype correlation for bone parameters. In addition, no difference was found in subjects treated with rhGh compared to untreated ones. In a previous study, Noordam et al. found a slight increase in bone cortical after 2 years of rhGH treatment [32].
In conclusion, despite the limited number of subjects and observational design, this is the first study to evaluate bone turnover markers, bone remodeling markers, and instrumental parameters of bone mineralization in a cohort of children with NS. The data that emerged indicate that alterations of the RAS/MAPK signaling pathway and the SHP2 protein are related to an increase in osteoclastic activity and, therefore, bone resorption, which over time could explain the tendency towards osteopenia/osteoporosis in these subjects. Future longitudinal studies in larger cohorts are needed to understand which subjects are more predisposed to skeletal demineralization and at what stage of life, and whether rhGH treatment started in the first years of life—in addition to improving height outcomes—can also maintain the balance between osteoblasts and osteoclasts, thus preserve bone health.
Conceptualization, M.F.F.; methodology, M.C., C.L., L.P. and R.V.; software, I.F., M.C. and P.G.; validation, M.F.F. and P.M.; formal analysis, L.P., I.F. and M.C.; investigation, F.U., R.V. and C.L.; data curation, M.C. and C.L.; writing—original draft preparation, I.F. and M.C.; writing—review and editing, M.F.F.; supervision, M.F.F. and P.M. All authors have read and agreed to the published version of the manuscript.
The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of IRCCS “Giovanni Paolo II” (protocol code 371 of 12 June 2024) for studies involving humans.
Informed consent was obtained from all subjects involved in the study. Written informed consent has been obtained from the patients to publish this paper.
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.
The authors declare no conflicts of interest.
The following abbreviations are used in this manuscript:
| BALP | Bone-specific alkaline phosphatase |
| BMD | Bone mineral density |
| BMI | Body mass index |
| BMI-SDS | Body mass index standard deviation score |
| CTX | C-terminal telopeptide cross-links of type I collagen |
| DEXA | Dual-energy X-ray absorptiometry |
| GH | Growth hormone |
| LZTR1 | Leucine zipper-like transcription regulator 1 |
| NS | Noonan syndrome |
| OC | Osteocalcin |
| OPG | Osteoprotegerin |
| P1NP | Procollagen type I N-terminal propeptide |
| PTH | Parathyroid hormone |
| PTPN11 | Protein tyrosine phosphatase non-receptor type 11 |
| RAS | Rat sarcoma viral oncogene homolog |
| RASopathies | Group of genetic disorders involving the RAS/MAPK pathway |
| RANKL | Receptor activator of nuclear factor kappa-B ligand |
| rhGH | Recombinant human growth hormone |
| SHOC2 | Leucine-rich repeat scaffold protein |
| SHP2 | Src homology-containing protein tyrosine phosphatase 2 |
| SOS1 | Son of sevenless homolog 1 |
| SDS | Standard deviation score |
| SPSS | Statistical Package for the Social Sciences |
Footnotes
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
Figure 1 Genotype distribution in NS population.
Main markers of bone metabolism and their functions.
| Function | Marker | Full Name | Biological Role |
|---|---|---|---|
| Bone Formation | BALP | Bone-specific Alkaline Phosphatase | Enzyme involved in bone matrix mineralization |
| P1NP | Procollagen type 1 N-terminal propeptide | Released during type I collagen synthesis, indicator of osteoblast activity | |
| Sclerostin | Sclerostin | Wnt -signaling pathway inhibitor, thus reducing bone formation | |
| Bone Resorption | CTX | C-terminal telopeptide of type I collagen | Released during collagen degradation, marker of bone resorption. |
| RANKL | Receptor Activator of Nuclear Factor κB Ligand | Stimulates osteoclast differentiation and activation | |
| OPG | Osteoprotegerin | Decoy receptor that binds RANKL, inhibiting bone resorption |
Baseline characteristics of enrolled subjects.
| NS (N = 28) | Controls (N = 35) | p Value | |
|---|---|---|---|
| Sex (M/F) | 20/8 | 21/14 | 0.3 |
| Age (yr) | 10.49 ± 6.02 | 8.6 ± 4.86 | 0.2 |
| Height (cm) | 123.26 ± 23.44 | 132.4 ± 19.8 | 0.09 |
| Height (SDS) | −2.08 ± 1.24 | −0.12 ± 0.91 | 0.0003 |
| Weight (Kg) | 27.30 ± 12.44 | 32.8 ± 11.1 | 0.07 |
| Weight (SDS) | −1.79 ± 1.38 | 0.05 ± 1.03 | 0.0002 |
| BMI (Kg/m2) | 17.0 ± 2.92 | 17.9 ± 2.4 | 0.4 |
| BMI (SDS) | −0.75 ± 1.24 | 0.11 ± 1.02 | 0.005 |
| Pre-pubertal n (%) | 18 (64.2) | 26 (74.3) | 0.4 |
Legend: Data are expressed as n (%) or mean ± standard deviation (SD). Significance levels: p < 0.05 (Student’s t-test or Chi-square test, as appropriate). BMI, body mass index; BMI-SDS, body mass index standard deviation score; Height-SDS, height standard deviation score; Kg, kilograms; yr, years.
Markers of bone turnover and bone remodeling in the study population.
| Variable | NS Subjects (n = 28) | Controls (n = 35) | p |
|---|---|---|---|
| Osteocalcin (ng/mL) | 73.8 ± 34.7 | 82.0 ± 31.2 | 0.32 a |
| P1NP (ng/mL) | 610.8 ± 242.5 | 690.5 ± 333.1 | 0.32 a |
| BALP (ug/L) | 73.5 (53.9–95.4) | 68.0 (60.8–76.3) | 0.27 b |
| CTX (ng/mL) | 1.8 ± 0.7 | 1.3±0.4 | 0.001 a |
| RANKL (pmol/L) | 2582.0 (1091.7–9105.7) | 1458.0 (342.0–6358.0) | 0.09 b |
| OPG (pmol/L) | 3.9 ± 1.7 | 3.6 ± 1.3 | 0.44 a |
| RANKL/OPG ratio | 9000.0 ± 3390.3 | 1570.5 ± 3092.1 | 0.134 |
| Sclerostin (pmol/L) | 17.0 (16.0–19.5) | 17.6 (15.2–19.7) | 0.93 b |
Legend: Data are presented as actual numbers (%) for proportions, mean + SD for normally distributed variables, and median with interquartile range for non-normally distributed variables. NS: Noonan syndrome; P1NP: procollagen type I N-terminal propeptide; BALP: bone-specific total alkaline phosphatase; CTX: C-terminal telopeptide cross-links of type I collagen; RANKL: soluble receptor activator of nuclear factor kappa-B ligand; OPG: osteoprotegerin. a Student t-test, values are expressed as mean ± SD; b Mann–Whitney U test, values are expressed as median and interquartile range.
Clinical and biochemical characteristics according to genotype.
| Variable | PTPN11+ | PTPN11− | p-Value |
|---|---|---|---|
| Age (years) | 10 ± 5 | 11 ± 8 | 0.972 |
| Male (%) | 13 (76%) | 7 (64%) | 0.671 |
| Height SDS | −2.1 ± 1.2 | −2.1 ± 1.4 | 0.995 |
| Weight SDS | −1.8 ± 1.2 | −1.7 ± 1.7 | 0.891 |
| BMI SDS | −0.8±1.2 | −0.7 ± 1.4 | 0.906 |
| Calcium (mg/dL) | 9.81 ± 0.47 | 9.88 ± 0.43 | 0.615 |
| Phosphate (mg/dL) | 4.71 ± 0.52 | 4.64 ± 0.41 | 0.669 |
| PTH (pg/mL) | 28 ± 12 | 33 ± 12 | 0.311 |
| 25-OH Vitamin D (ng/mL) | 26 ± 13 | 28 ± 12 | 0.556 |
| Osteocalcin (ng/mL) | 87 ± 37 | 73 ± 27 | 0.710 |
| P1NP (ng/mL) | 634 ± 270 | 554 ± 162 | 0.759 |
| BALP (ug/L) | 72 ± 35 | 57 ± 23 | 0.347 |
| CTX (ng/mL) | 1.96 ± 0.74 | 1.74 ± 0.81 | 0.470 |
| RANKL (pmol/L) | 6780 ± 8492 | 5422 ± 5647 | 0.443 |
| OPG (pmol/L) | 4.0 ± 1.6 | 3.8 ± 2.0 | 0.978 |
| BMD (Z-score) | −1.0 ± 1.1 | −1.8 ± 1.4 | 0.1 |
Legend: Data are presented as actual numbers (%) for proportions, mean ± SD for normally distributed variables, and median with interquartile range for non-normally distributed variables. P1NP: procollagen type I N-terminal propeptide; BALP: bone-specific total alkaline phosphatase; CTX: C-terminal telopeptide cross-links of type I collagen; RANKL: soluble receptor activator of nuclear factor kappa-B ligand; OPG: osteoprotegerin. BMD: bone mineral density.
1. Roberts, A.E.; Allanson, J.E.; Tartaglia, M.; Gelb, B.D. Noonan syndrome. Lancet; 2013; 381, pp. 333-342. [DOI: https://dx.doi.org/10.1016/S0140-6736(12)61023-X]
2. Libraro, A.; D’Ascanio, V.; Cappa, M.; Chiarito, M.; Digilio, M.C.; Einaudi, S.; Grandone, A.; Maghnie, M.; Mazzanti, L.; Mussa, A.
3. Faienza, M.F.; Meliota, G.; Mentino, D.; Ficarella, R.; Gentile, M.; Vairo, U.; D’amato, G. Cardiac phenotype and gene mutations in RASopathies. Genes; 2024; 15, 1015. [DOI: https://dx.doi.org/10.3390/genes15081015]
4. Zenker, M. Clinical overview on RASopathies. Am. J. Med. Genet. Pt. C; 2022; 190, pp. 414-424. [DOI: https://dx.doi.org/10.1002/ajmg.c.32015]
5. Aoki, Y.; Niihori, T.; Inoue, S.; Matsubara, Y. Recent advances in RASopathies. J. Hum. Genet.; 2016; 61, pp. 33-39. [DOI: https://dx.doi.org/10.1038/jhg.2015.114]
6. Simanshu, D.K.; Nissley, D.V.; McCormick, F. RAS proteins and their regulators in human disease. Cell; 2017; 170, pp. 17-33. [DOI: https://dx.doi.org/10.1016/j.cell.2017.06.009]
7. Tartaglia, M.; Gelb, B.D. Disorders of dysregulated signal traffic through the RAS-MAPK pathway: Phenotypic spectrum and molecular mechanisms. Ann. N. Y. Acad. Sci.; 2010; 1214, pp. 99-121. [DOI: https://dx.doi.org/10.1111/j.1749-6632.2010.05790.x]
8. Tartaglia, M.; Mehler, E.L.; Goldberg, R.; Zampino, G.; Brunner, H.G.; Kremer, H.; Van Der Burgt, I.; Crosby, A.H.; Ion, A.; Jeffery, S.
9. Johnston, J.J.; Van Der Smagt, J.J.; Rosenfeld, J.A.; Pagnamenta, A.T.; Alswaid, A.; Baker, E.H.; Blair, E.; Borck, G.; Brinkmann, J.; Craigen, W.
10. Tartaglia, M.; Aoki, Y.; Gelb, B.D. The molecular genetics of RASopathies : An update on novel disease genes and new disorders. Am. J. Med. Genet. Pt. C; 2022; 190, pp. 425-439. [DOI: https://dx.doi.org/10.1002/ajmg.c.32012]
11. Choudhry, K.S.; Grover, M.; Tran, A.A.; O’Brian Smith, E.; Ellis, K.J.; Lee, B.H. Decreased bone mineralization in children with noonan syndrome: Another consequence of dysregulated RAS MAPKinase pathway?. Mol. Genet. Metab.; 2012; 106, pp. 237-240. [DOI: https://dx.doi.org/10.1016/j.ymgme.2012.04.003] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/22551697]
12. Malaquias, A.C.; Brasil, A.S.; Pereira, A.C.; Arnhold, I.J.P.; Mendonca, B.B.; Bertola, D.R.; Jorge, A.A.L. growth standards of patients with noonan and noonan-like syndromes with mutations in the RAS/MAPK pathway. Am. J. Med. Genet. Pt. A; 2012; 158A, pp. 2700-2706. [DOI: https://dx.doi.org/10.1002/ajmg.a.35519] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/22887833]
13. Delagrange, M.; Rousseau, V.; Cessans, C.; Pienkowski, C.; Oliver, I.; Jouret, B.; Cartault, A.; Diene, G.; Tauber, M.; Salles, J.-P.
14. Baldassarre, G.; Mussa, A.; Carli, D.; Molinatto, C.; Ferrero, G.B. Constitutional bone impairment in noonan syndrome. Am. J. Med. Genet. Pt. A; 2017; 173, pp. 692-698. [DOI: https://dx.doi.org/10.1002/ajmg.a.38086]
15. Reyad, M.; Murad, M.R.; Sobhy, A.; Hassan, A.M.; Nassar, O.; Hassan, A. Noonan syndrome and osteoporosis: A comprehensive case study and literature review. ASIDE Case Rep.; 2025; 1, pp. 1-4. [DOI: https://dx.doi.org/10.71079/ASIDE.CR.02062520]
16. Stevenson, D.A.; Viscogliosi, G.; Leoni, C. Bone health in RASopathies. Am. J. Med. Genet. Pt. C; 2022; 190, pp. 459-470. [DOI: https://dx.doi.org/10.1002/ajmg.c.32020]
17. Brescia, V.; Lovero, R.; Fontana, A.; Zerlotin, R.; Colucci, S.C.; Grano, M.; Cazzolla, A.P.; Di Serio, F.; Crincoli, V.; Faienza, M.F. Reference intervals (RIs) of the bone turnover markers (BTMs) in children and adolescents: A proposal for effective use. Biomedicines; 2024; 13, 34. [DOI: https://dx.doi.org/10.3390/biomedicines13010034]
18. D’Amato, G.; Brescia, V.; Fontana, A.; Natale, M.P.; Lovero, R.; Varraso, L.; Di Serio, F.; Simonetti, S.; Muggeo, P.; Faienza, M.F. Biomarkers and biochemical indicators to evaluate bone metabolism in preterm neonates. Biomedicines; 2024; 12, 1271. [DOI: https://dx.doi.org/10.3390/biomedicines12061271]
19. Krishnan, V. Regulation of bone mass by Wnt signaling. J. Clin. Investig.; 2006; 116, pp. 1202-1209. [DOI: https://dx.doi.org/10.1172/JCI28551]
20. Theill, L.E.; Boyle, W.J.; Penninger, J.M. RANK-L and RANK: T cells, bone loss, and mammalian evolution. Annu. Rev. Immunol.; 2002; 20, pp. 795-823. [DOI: https://dx.doi.org/10.1146/annurev.immunol.20.100301.064753]
21. Brunetti, G.; D’Amato, G.; Chiarito, M.; Tullo, A.; Colaianni, G.; Colucci, S.; Grano, M.; Faienza, M.F. An update on the role of RANKL–RANK/osteoprotegerin and WNT-ß-catenin signaling pathways in pediatric diseases. World J. Pediatr.; 2019; 15, pp. 4-11. [DOI: https://dx.doi.org/10.1007/s12519-018-0198-7] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/30343446]
22. Cacciari, E.; Milani, S.; Balsamo, A.; Dammacco, F.; De Luca, F.; Chiarelli, F.; Pasquino, A.; Tonini, G.; Vanelli, M. Italian cross-sectional growth charts for height, weight and BMI (6–20 y). Eur. J. Clin. Nutr.; 2002; 56, pp. 171-180. [DOI: https://dx.doi.org/10.1038/sj.ejcn.1601314]
23. Tanner, J.M.; Whitehouse, R.H. Clinical longitudinal standards for height, weight, height velocity, weight velocity, and stages of puberty. Arch. Dis. Child.; 1976; 51, pp. 170-179. [DOI: https://dx.doi.org/10.1136/adc.51.3.170] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/952550]
24. Johnson, B.; Goldberg-Strassler, D.; Gripp, K.; Thacker, M.; Leoni, C.; Stevenson, D. Function and disability in children with costello syndrome and cardiofaciocutaneous syndrome. Am. J. Med. Genet. Pt. A; 2015; 167, pp. 40-44. [DOI: https://dx.doi.org/10.1002/ajmg.a.36828] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/25346259]
25. Leoni, C.; Triumbari, E.K.A.; Vollono, C.; Onesimo, R.; Podagrosi, M.; Giorgio, V.; Kuczynska, E.; Veltri, S.; Tartaglia, M.; Zampino, G. Pain in individuals with RASopathies: Prevalence and clinical characterization in a sample of 80 affected patients. Am. J. Med. Genet. Pt. A; 2019; 179, pp. 940-947. [DOI: https://dx.doi.org/10.1002/ajmg.a.61111]
26. Stevenson, D.; Schwarz, E.; Carey, J.; Viskochil, D.; Hanson, H.; Bauer, S.; Cindy Weng, H.-Y.; Greene, T.; Reinker, K.; Swensen, J.
27. Kim, H.K.; Feng, G.-S.; Chen, D.; King, P.D.; Kamiya, N. Targeted disruption of Shp2 in chondrocytes leads to metachondromatosis with multiple cartilaginous protrusions. J. Bone Miner. Res.; 2014; 29, pp. 761-769. [DOI: https://dx.doi.org/10.1002/jbmr.2062]
28. Yang, W.; Wang, J.; Moore, D.C.; Liang, H.; Dooner, M.; Wu, Q.; Terek, R.; Chen, Q.; Ehrlich, M.G.; Quesenberry, P.J.
29. Matsushita, T.; Chan, Y.Y.; Kawanami, A.; Balmes, G.; Landreth, G.E.; Murakami, S. Extracellular signal-regulated kinase 1 (ERK1) and ERK2 play essential roles in osteoblast differentiation and in supporting osteoclastogenesis. Mol. Cell. Biol.; 2009; 29, pp. 5843-5857. [DOI: https://dx.doi.org/10.1128/MCB.01549-08]
30. Sebastian, A.; Matsushita, T.; Kawanami, A.; Mackem, S.; Landreth, G.E.; Murakami, S. Genetic inactivation of ERK1 and ERK2 in chondrocytes promotes bone growth and anlarges the spinal canal. J. Orthop. Res.; 2011; 29, pp. 375-379. [DOI: https://dx.doi.org/10.1002/jor.21262]
31. Wang, L.; Huang, J.; Moore, D.C.; Zuo, C.; Wu, Q.; Xie, L.; Von Der Mark, K.; Yuan, X.; Chen, D.; Warman, M.L.
32. Noordam, C.; Span, J.; Van Rijn, R.R.; Gomes-Jardin, E.; Van Kuijk, C.; Otten, B.J. Bone mineral density and body composition in noonan’s syndrome: Effects of growth hormone treatment. J. Pediatr. Endocrinol. Metab.; 2002; 15, pp. 81-87. [DOI: https://dx.doi.org/10.1515/JPEM.2002.15.1.81]
© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.
Details
; Lattanzio Crescenza 1 ; Vitale Rossella 1 ; Urbano Flavia 1 ; Guida Pietro 3 ; Piacente, Laura 4 ; Muggeo Paola 5
; Faienza, Maria Felicia 4
1 Giovanni XXIII Pediatric Hospital, University of Bari “A. Moro”, 70124 Bari, Italy; [email protected] (M.C.); [email protected] (C.L.); [email protected] (R.V.); [email protected] (F.U.)
2 Department of Medicine and Surgery, LUM University, 70010 Casamassima, Italy; [email protected], Neonatology Department, Regional General Hospital “F. Miulli”, 70021 Bari, Italy; [email protected]
3 Neonatology Department, Regional General Hospital “F. Miulli”, 70021 Bari, Italy; [email protected]
4 Pediatric Unit, Department of Precision and Regenerative Medicine and Ionian Area, University “A. Moro”, 70124 Bari, Italy; [email protected]
5 Department of Pediatric Oncology and Hematology, University Hospital of Policlinic, 70124 Bari, Italy; [email protected]