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La recombinación entre CYP21A2-TNXB y sus respectivos pseudogenes (CYP21A1P-TNXA) da lugar a quimeras responsables del síndrome CAH-X (SCAH-X). Los pacientes con este síndrome presentan manifestaciones clínicas de hiperplasia suprarrenal congénita (HSC) y síndrome de Ehlers-Danlos (SED). La descripción del SCAH-X es reciente y es limitado el número de estudios disponibles. El objetivo de este trabajo es poner a punto un abordaje para la detección de todos los tipos de quimeras CAH-X, determinar su frecuencia y la distribución en población española así como valorar la expresividad clínica en un grupo de pacientes.

Several letters to the editor are presented in response to articles in previous issues including "Citrate regional anticoagulation in continuous renal replacement therapy techniques," and "prenatel counselling of 21-hdroxylase deficiency."

Noonan syndrome (NS) is a relatively common genetic condition characterised by short stature, congenital heart defects, and distinctive facial features. NS and other clinically overlapping conditions such as NS with multiple lentigines (formerly called LEOPARD syndrome), cardiofaciocutaneous syndrome, or Costello syndrome, are caused by mutations in genes encoding proteins of the RAS-MAPKinases pathway. Because of this shared mechanism, these conditions have been collectively termed «RASopathies». Despite the recent advances in molecular genetics, nearly 20% of patients still lack a genetic cause, and diagnosis is still made mainly on clinical grounds. NS is a clinically and genetically heterogeneous condition, with variable expressivity and a changing phenotype with age, and affects multiple organs and systems. Therefore, it is essential that physicians involved in the care of these patients are familiarised with their manifestations and the management recommendations, including management of growth and development. Data on growth hormone treatment efficacy are sparse, and show a modest response in height gains, similar to that observed in Turner syndrome. The role of RAS/MAPK hyper-activation in the pathophysiology of this group of disorders offers a unique opportunity for the development of targeted approaches., (Copyright © 2020 Asociación Española de Pediatría. Publicado por Elsevier España, S.L.U. All rights reserved.)

. LEOPARD syndrome 2 (LS-2) (OMIM #611554) is a rare, dominantly inherited genetic disorder affecting multiple organ systems. We report two unrelated females of different ages whose phenotype fits best in the category of LEOPARD syndrome, both with proven mutations in the RAF1 gene not previouslyreported in pediatric patients. In our 10-year-old patient, who was negative in the PTPN11 gene analysis but involving the RAF1 gene in a complementary analysis, the sequence variant Ser257Leu (770C > T, exon 7) was detected, which previously had been reported in only one 35-year-old woman with LS. The second patient was a two-year-old female infant with Ser259Leu mutation in the same gene, described in several patients with Noonan syndrome (NS) but not in LS patients of any age. The first girl had ventricular and supraventricular extrasystoles, and the second had episodes of paroxysmal supraventricular tachycardia. Echocardiographic examination revealed biventricular obstructive hypertrophic cardiomyopathy in both patients.

Aim: The aim of the study was to identify patients with transitory elevation (TE) of 17-hydroxyprogesterone (17-OHP) using neonatal screening for congenital adrenal hyperplasia due to 21-hydroxylase deficiency (21-OHD) and to compare them with patients with 21-OHD., Methods: This was a retrospective study of patients with high 17-OHP levels detected during newborn screening in Madrid, Spain., Results: 17-OHP levels were significantly higher in the 33 21-OHD patients, who tended to present hyponatraemia and hyperkalemia. The TE-17-OHP group was characterized by normal initial physical examination (88.8% vs. 39.4%), lower gestational age and a higher number of stressful perinatal factors. 17-OHP levels decreased spontaneously in this group. Molecular diagnosis allowed us to discard the most frequent mutations associated with 21-OHD., Conclusions: Newborns with slightly increased 17-OHP levels and normal results for physical examination, acid-base equilibrium, glycemia, electrolytes and perinatal stress factors should be carefully evaluated. Decisions on treatment should be postponed until these results are available.

Background and Objective: Congenital Adrenal Hyperplasia (CAH) is not an infrequent genetic disorder for which mutation-based analysis for CYP21A2 gene is a useful tool. Contrarily to salt-wasting forms the basic mutation screening accounts only for 83% of simple virilising (SV) phenotypes. Rare alleles with a local distribution not included in the basic panel may reduce its diagnostic accuracy. Our aim is to explore underlying prevalent mutations among our partially characterised SV forms and to evaluate their potential impact in the mutation screening., Patients and Methods: Preliminary study: CYP21A2 gene sequencing in 13 SV patients partially characterised. Retrospective targeted study: 2,097 DNA samples (561 patients) were re-analysed for p.R426H mutation. Prospective targeted study: incorporation of the p.R426H mutation to the initial exploration of CAH in 1,041 DNA samples to validate this extended screening., Results: p.R426H mutation was detected in five patients in the preliminary analysis and in ten more during targeted studies. A frequency for this mutation was 0.71% in the whole group and 7.14% in SV forms. Associated haplotypes were identical thus suggesting a preferential dissemination. The observed phenotypes correlated and confirmed the moderate-to-severe effect on the enzymatic activity., Conclusions: Our data relative to allelic frequency of the p.R426H mutation and its strong association to SV forms justify the incorporation of the p.R426H mutation into the basic screening panel because of the significant improvement in the initial characterization of affected patients, especially among those with SV forms. Two new cases detected remark the usefulness of this novel approach., (Copyright 2009 Elsevier España, S.L. All rights reserved.)

Background and Objective: Nonclassical congenital adrenal hyperplasia due to 21-hydroxylase deficiency mainly manifests with symptoms and signs of hyperandrogenism, which are usually obvious in women and sometimes obvious in children or adolescents, but are rarely observed in adult men especially with increasing age. Male pattern alopecia is considered an androgenetic and age-related symptom. However, its early appearance should raise the suspicion of an underlying endocrinological disease, and biochemical screening should be done., Patients and Method: Here we present the case of 2 siblings (female and male) where the man complains about premature alopecia., Results: Molecular study of CYP21A2 revealed that both siblings were compound heterozygotes for the mild mutation (V281L) and for a novel nonsense mutation (Y336X)., Conclusions: Given the high prevalence of carriers with severe mutations, we discuss the risk for such patients of conceiving a child with a classical disease and the need for a reliable molecular diagnosis in order to provide accurate genetic counselling.

Background: Achondroplasia, the most common type of genetic dwarfism characterised by disproportionate short stature and other skeletal anomalies, results from a defect in the maturation of the chondrocytes in the growth plate cartilage. Hypochondroplasia, considered allelic to achondroplasia is clinically and genetically heterogeneous. Recent studies have mapped the gene on chromosome 4p16.3, and frequent mutations in the fibroblast growth factor 3 (FGFR3) have been described in these diseases in other populations., Patients and Methods: Analysis of the FGFR3 gene mutations Gly380Arg and Asn540Lys in 20 Spanish patients (10 achondroplasic, 6 hypochondroplasic and 4 with skeletal dysplasias with some phenotypic and radiological characteristics of hypochondroplasia) by PCR and restriction analysis., Results: All the achondroplasic patients have shown the same mutation (Gly380Arg) in the transmembrane domain of the receptor. Five hypochondroplasic patients presented the mutation Asn540Lys in the proximal thirosine kinase domain., Conclusions: Achondroplasia in this sample from Spanish patients is also homogeneous in its molecular basis. Genetic heterogeneity has been found in hypochondroplasia corresponding with the phenotypic diversity in this disease. Molecular analysis of FGFR3 may be an additional diagnostic tool and facilitates genetic counselling in these chondrodysplasias.