Isabel González-Casado

Heterozygous NPR2 Mutations Cause Disproportionate Short Stature, Similar to Léri-Weill Dyschondrosteosis

CONTEXT SHOX mutations have been detected in approximately 70% of Léri-Weill dyschondrosteosis (LWD) and approximately 2.5% of idiopathic short stature (ISS) cases, suggesting the implication of other genes or loci. The recent identification of NPR2 mutations in ISS suggested that NPR2 mutations may also be involved in disproportionate short stature. OBJECTIVE The objective of the study was to investigate whether NPR2 mutations can account for a proportion of the cases referred for LWD and ISS in whom no SHOX mutation was detected. PATIENTS AND METHODS We undertook NPR2 mutation screening in 173 individuals referred for suspected LWD and 95 for ISS, with no known defect in SHOX or its enhancers. Intracellular localization and natriuretic peptide precursor C-dependent guanylate cyclase activity were determined for the identified NPR2 variants. RESULTS Eight NPR2 variants were identified in nine individuals, seven referred for suspected LWD and two for ISS. Six were demonstrated to affect NPR-B cell trafficking and/or its ability to synthesize cyclic GMP (cGMP) under response to natriuretic peptide precursor C/brain natriuretic peptide stimulation. All pathogenic mutations were detected in the suspected LWD referral group (∼3%). Interestingly, one of these patients is currently being treated with recombinant human GH and in contrast to previous reports is showing a positive response to the treatment. CONCLUSIONS NPR2 mutations account for approximately 3% of patients with disproportionate short stature and/or clinical or radiographic indicators of SHOX deficiency and in whom no SHOX defect has been identified. However, no patient has yet presented with Madelung deformity. Thus, NPR2 should be screened in the SHOX-negative LWD referrals.

Metabolomic approach to the nutraceutical effect of rosemary extract plus ω-3 PUFAs in diabetic children with capillary electrophoresis

Type 1 diabetes mellitus is a major endocrine disorder, affecting approximately 5% of the worlds population. It not only leads to hyperglycaemia but also causes many complications, and numerous studies have demonstrated that oxidative stress contributes to these complications. As a new strategy to improve the oxidative damage in diabetes, interest has grown in the usage of natural antioxidants, even more in the long term. Among them, Rosmarinus officinalis (rosemary) has been widely accepted as one of the species with the highest antioxidant activity. In addition, omega-3 polyunsaturated fatty acids were efficient in delaying and decreasing cardiovascular risk factors associated with diabetes. Type 1 diabetic children and the corresponding controls were enrolled in the assay. The aim was evaluating the effect of a special additive containing rosemary extract, vitamin E and PUFAs added to their standard diet through the meat. In the analytical point of view, a metabolomic approach with CE-UV was used to detect possible differences in urine of diabetic children as compared to controls. After the application of the appropriate multivariate statistical tools, clear differences could be observed between treated and non-treated diabetic children and some of the metabolites associated could be identified. This was specially challenging as most of the clinical biochemical parameters measured by target analysis showed no differences between the groups.

A New Overgrowth Syndrome is Due to Mutations in RNF125.

Overgrowth syndromes (OGS) are a group of disorders in which all parameters of growth and physical development are above the mean for age and sex. We evaluated a series of 270 families from the Spanish Overgrowth Syndrome Registry with no known OGS. We identified one de novo deletion and three missense mutations in RNF125 in six patients from four families with overgrowth, macrocephaly, intellectual disability, mild hydrocephaly, hypoglycemia, and inflammatory diseases resembling Sjögren syndrome. RNF125 encodes an E3 ubiquitin ligase and is a novel gene of OGS. Our studies of the RNF125 pathway point to upregulation of RIG‐I‐IPS1‐MDA5 and/or disruption of the PI3K‐AKT and interferon signaling pathways as the putative final effectors.

Two novel POC1A mutations in the primordial dwarfism, SOFT syndrome: Clinical homogeneity but also unreported malformations.

Primordial dwarfism encompasses rare conditions characterized by severe intrauterine growth retardation and growth deficiency throughout life. Recently, three POC1A mutations have been reported in six families with the primordial dwarfism, SOFT syndrome (Short stature, Onychodysplasia, Facial dysmorphism, and hypoTrichosis). Using a custom‐designed Next‐generation sequencing skeletal dysplasia panel, we have identified two novel homozygous POC1A mutations in two individuals with primordial dwarfism. The severe growth retardation and the facial profiles are strikingly similar between our patients and those described previously. However, one of our patients was diagnosed with severe foramen magnum stenosis and subglottic tracheal stenosis, malformations not previously associated with this syndrome. Our findings confirm that POC1A mutations cause SOFT syndrome and that mutations in this gene should be considered in patients with severe pre‐ and postnatal short stature, symmetric shortening of long bones, triangular facies, sparse hair and short, thickened distal phalanges.

Hypoinsulinaemic, hypoketotic hypoglycaemia due to mosaic genetic activation of PI3-kinase

Objective Genetic activation of the insulin signal-transducing kinase AKT2 causes syndromic hypoketotic hypoglycaemia without elevated insulin. Mosaic activating mutations in class 1A phospatidylinositol-3-kinase (PI3K), upstream from AKT2 in insulin signalling, are known to cause segmental overgrowth, but the metabolic consequences have not been systematically reported. We assess the metabolic phenotype of 22 patients with mosaic activating mutations affecting PI3K, thereby providing new insight into the metabolic function of this complex node in insulin signal transduction. Methods Three patients with megalencephaly, diffuse asymmetric overgrowth, hypoketotic, hypoinsulinaemic hypoglycaemia and no AKT2 mutation underwent further genetic, clinical and metabolic investigation. Signalling in dermal fibroblasts from one patient and efficacy of the mTOR inhibitor Sirolimus on pathway activation were examined. Finally, the metabolic profile of a cohort of 19 further patients with mosaic activating mutations in PI3K was assessed. Results In the first three patients, mosaic mutations in PIK3CA (p.Gly118Asp or p.Glu726Lys) or PIK3R2 (p.Gly373Arg) were found. In different tissue samples available from one patient, the PIK3CA p.Glu726Lys mutation was present at burdens from 24% to 42%, with the highest level in the liver. Dermal fibroblasts showed increased basal AKT phosphorylation which was potently suppressed by Sirolimus. Nineteen further patients with mosaic mutations in PIK3CA had neither clinical nor biochemical evidence of hypoglycaemia. Conclusions Mosaic mutations activating class 1A PI3K cause severe non-ketotic hypoglycaemia in a subset of patients, with the metabolic phenotype presumably related to the extent of mosaicism within the liver. mTOR or PI3K inhibitors offer the prospect for future therapy.

Familial glucocorticoid deficiency due to compound heterozygosity of two novel MC2R mutations.

Abstract Familial glucocorticoid deficiency (FGD) is a rare autosomal recessive disorder characterized by isolated glucocorticoid deficiency. Mutations in the ACTH receptor (melanocortin 2 receptor, MC2R) or the MC2R accessory protein (MRAP) cause FGD types 1 and 2, respectively. A 2-year-old adopted Chinese girl presented with hypertonic seizures associated with hypoglycemia, skin hyperpigmentation, muscle weakness and mild jaundice. Hormonal analyses revealed high ACTH, low serum cortisol along with normal blood electrolytes. On hydrocortisone supplementation, the disease symptoms disappeared and the child recovered, although further episodes occurred with infection. To date, her physical and neurocognitive development progress is normal. A clinical diagnosis of FGD was given. We undertook MC2R and MRAP mutation screening. Two novel MC2R mutations were identified: p.D107G localized in the transmembrane region, predicted to be trafficking-competent but is unable to bind to ACTH, and p.R145C, situated in the second intracellular loop, predicted to be trafficking-defective.

Identification of eight new mutations in the GCK gene by DHPLC screening in a Spanish population.

Maturity onset diabetes of the young (MODY) is a genetically heterogeneous disorder characterized by autosomal dominant inheritance, altered function of pancreatic beta cells and early onset diabetes mellitus, usually before 25 years old. The prevalence of specific mutations of MODY genes differs considerably among different countries. In this study we analyzed 53 index cases from unrelated MODY families who are potential carriers of mutations in GCK gene. In addition, 122 relatives were also studied. We have identified eight new mutations in the GCK gene. One of them is a non-frameshift deletion involving Lysine 143. This amino acid is part of the conserved stretch of basic residues (KHKKL) which spans from residue 140 to 144. The non-frameshift deletion might implicate the affinity of GCK for GCKRP, and potentially the abnormal nuclear localization of GCK. Additional studies should be performed to confirm this possibility.

Identification of 15 novel partial SHOX deletions and 13 partial duplications, and a review of the literature reveals intron 3 to be a hotspot region

Short stature homeobox gene (SHOX) is located in the pseudoautosomal region 1 of the sex chromosomes. It encodes a transcription factor implicated in the skeletal growth. Point mutations, deletions or duplications of SHOX or its transcriptional regulatory elements are associated with two skeletal dysplasias, Léri–Weill dyschondrosteosis (LWD) and Langer mesomelic dysplasia (LMD), as well as in a small proportion of idiopathic short stature (ISS) individuals. We have identified a total of 15 partial SHOX deletions and 13 partial SHOX duplications in LWD, LMD and ISS patients referred for routine SHOX diagnostics during a 10 year period (2004–2014). Subsequently, we characterized these alterations using MLPA (multiplex ligation-dependent probe amplification assay), fine-tiling array CGH (comparative genomic hybridation) and breakpoint PCR. Nearly half of the alterations have a distal or proximal breakpoint in intron 3. Evaluation of our data and that in the literature reveals that although partial deletions and duplications only account for a small fraction of SHOX alterations, intron 3 appears to be a breakpoint hotspot, with alterations arising by non-allelic homologous recombination, non-homologous end joining or other complex mechanisms.

Pyogenic granuloma, an unusual presentation of peripubertal vaginal bleeding. Case report and review of the literature.

Abstract Pyogenic granuloma, also named lobular capillary hemangioma, is a common proliferative vascular lesion known as a benign condition despite its rapid growth. It may appear in any cutaneous or mucosal surface but is usually restricted to the oral cavity. It is characterized by a friable mulberry-like lesion that can be sessile or pedunculated. Bleeding is usually its first clinical manifestation. Locations on respiratory, digestive and genital tracts are uncommon and sporadic. We describe the occurrence of an intravaginal pyogenic granuloma in a peripubertal girl with recurrent vaginal bleeding. This is the first reported case of a genital tract lobular capillary hemangioma in pediatric age to our knowledge. Therefore, we suggest this entity in the differential diagnosis of an unclear peripubertal vaginal bleeding.

Multiple SLC26A2 mutations occurring in a three-generational family

Multiple epiphyseal dysplasias (MED) are a group of heterogeneous skeletal dysplasias, which share a common phenotype: short stature, skeletal deformities, joint pain and early onset osteoarthritis. Mutations in COMP account for approximately half of autosomal dominant MED cases whilst SLC26A2 mutations account for ∼25% of the recessive cases in the Caucasian population. We present here an interesting family, which was thought to initially have an autosomal dominant skeletal dysplasia. Using a targeted sequencing skeletal dysplasia panel, the proband was found to be a compound heterozygote for two mutations in SLC26A2, one novel mutation, p.Ser522Phe and the other, the common mutation, p.Arg279Trp. In addition to the classical characteristics of MED, she presented with an atypical feature, bilateral synostoses between the 2nd and 3rd metatarsals. The parents were confirmed to be heterozygous for the two mutations but interestingly, the maternal grandfather, who had MED, was found to be homozygous for the common SLC26A2 mutation.