Lidia Castro-Feijoo

Functional Consequences of Seven Novel Mutations in the CYP11B1 Gene: Four Mutations Associated with Nonclassic and Three Mutations Causing Classic 11β-Hydroxylase Deficiency

CONTEXT Steroid 11beta-hydroxylase (CYP11B1) deficiency (11OHD) is the second most common form of congenital adrenal hyperplasia (CAH). Cases of nonclassic 11OHD are rare compared with the incidence of nonclassic 21-hydroxylase deficiency. OBJECTIVE The aim of the study was to analyze the functional consequences of seven novel CYP11B1 mutations (p.M88I, p.W116G, p.P159L, p.A165D, p.K254_A259del, p.R366C, p.T401A) found in three patients with classic 11OHD, two patients with nonclassic 11OHD, and three heterozygous carriers for CYP11B1 mutations. METHODS We conducted functional studies employing a COS7 cell in vitro expression system comparing wild-type (WT) and mutant CYP11B1 activity. Mutants were examined in a computational three-dimensional model of the CYP11B1 protein. RESULTS All mutations (p.W116G, p.A165D, p.K254_A259del) found in patients with classic 11OHD have absent or very little 11beta-hydroxylase activity relative to WT. The mutations detected in patients with nonclassic 11OHD showed partial functional impairment, with one patient being homozygous (p.P159L; 25% of WT) and the other patient compound heterozygous for a novel mild p.M88I (40% of WT) and the known severe p.R383Q mutation. The two mutations detected in heterozygous carriers (p.R366C, p.T401A) also reduced CYP11B1 activity by 23 to 37%, respectively. CONCLUSION Functional analysis results allow for the classification of novel CYP11B1 mutations as causative for classic and nonclassic 11OHD, respectively. Four partially inactivating mutations are predicted to result in nonclassic 11OHD. These findings double the number of mild CYP11B1 mutations previously described as associated with mild 11OHD. Our data are important to predict phenotypic expression and provide important information for clinical and genetic counseling in 11OHD.

Central Precocious Puberty in Children Living in Spain: Incidence, Prevalence, and Influence of Adoption and Immigration

CONTEXT No epidemiological data are available on central precocious puberty (CPP) in the general population or in adopted or immigrant children in Spain. OBJECTIVE We aimed to study the incidence and prevalence of CPP, assess the risk of developing this disorder among adopted and immigrant children, and analyze the predictive variables of CPP associated with intracranial pathology. DESIGN, SETTINGS, AND PATIENTS An observational study of children diagnosed with CPP in Spain was carried out between January 2008 and January 2010. A computer program was designed to process clinical and biological data and information on 250 patients treated in 34 pediatric endocrinology units throughout the country. RESULTS Of the patients registered, 226 were girls and 24 were boys. The global incidence rate of CPP was 5.66 cases per million person-years at risk, with an annual incidence ranging between 0.02 and 1.07 new cases per 100,000. The relative risk of CPP in domestic and internationally adopted children compared with those born in Spain was 27.82 (19.99-38.77), whereas the relative risk among immigrants was 1.55 (0.97-2.38). A logistic regression model developed for the study showed that the combined effect of four variables had a significant influence over the presence of organic disease: being male, having been adopted, age at diagnosis, and estimation of adult height. CONCLUSIONS CPP is a rare disease whose risk markedly increases with both national and international adoption but is not influenced by immigration. These results suggest a psychological influence on CPP.

Hypochondroplasia and acanthosis nigricans: a new syndrome due to the p.Lys650Thr mutation in the fibroblast growth factor receptor 3 gene?

BACKGROUND Hypochondroplasia (HCH) is a skeletal dysplasia inherited in an autosomal dominant manner due, in most cases, to mutations in the fibroblast growth factor receptor 3 (FGFR3). Acanthosis nigricans (AN) is a velvety and papillomatous pigmented hyperkeratosis of the skin, which has been recognized in some genetic disorders more severe than HCH involving the FGFR3 gene. OBJECTIVE AND DESIGN After initial study of the proband, who had been consulted for short stature and who also presented AN, the study was extended to the patients mother and to 12 additional family members. METHODS Clinical, biochemical and radiological studies were performed on the family. In addition, exons 11 and 13 of FGFR3 were analyzed. RESULTS The proband and ten relatives presented HCH plus AN and the analysis of FGFR3 showed the p.Lys650Thr mutation. The members with normal phenotypes were non-carriers of the mutation. CONCLUSION This is the first report of a large pedigree with the clinical phenotype of HCH plus AN due to a FGFR3 mutation, p.Lys650Thr. This finding demonstrates the coexistence of both conditions due to the same mutation and it might represent a true complex, which should be further established by searching for AN in mild HCH patients or for HCH in patients with AN.

Evolutionary Analyses of Entire Genomes Do Not Support the Association of mtDNA Mutations with Ras/MAPK Pathway Syndromes

Background There are several known autosomal genes responsible for Ras/MAPK pathway syndromes, including Noonan syndrome (NS) and related disorders (such as LEOPARD, neurofibromatosis type 1), although mutations of these genes do not explain all cases. Due to the important role played by the mitochondrion in the energetic metabolism of cardiac muscle, it was recently proposed that variation in the mitochondrial DNA (mtDNA) genome could be a risk factor in the Noonan phenotype and in hypertrophic cardiomyopathy (HCM), which is a common clinical feature in Ras/MAPK pathway syndromes. In order to test these hypotheses, we sequenced entire mtDNA genomes in the largest series of patients suffering from Ras/MAPK pathway syndromes analyzed to date (n = 45), most of them classified as NS patients (n = 42). Methods/Principal Findings The results indicate that the observed mtDNA lineages were mostly of European ancestry, reproducing in a nutshell the expected haplogroup (hg) patterns of a typical Iberian dataset (including hgs H, T, J, and U). Three new branches of the mtDNA phylogeny (H1j1, U5b1e, and L2a5) are described for the first time, but none of these are likely to be related to NS or Ras/MAPK pathway syndromes when observed under an evolutionary perspective. Patterns of variation in tRNA and protein genes, as well as redundant, private and heteroplasmic variants, in the mtDNA genomes of patients were as expected when compared with the patterns inferred from a worldwide mtDNA phylogeny based on more than 8700 entire genomes. Moreover, most of the mtDNA variants found in patients had already been reported in healthy individuals and constitute common polymorphisms in human population groups. Conclusions/Significance As a whole, the observed mtDNA genome variation in the NS patients was difficult to reconcile with previous findings that indicated a pathogenic role of mtDNA variants in NS.

Kallmann's syndrome with a novel missense mutation in the KAL1 gene that modifies the major cell adhesion site of the anosmin-1 protein.

Kallmanns syndrome (KS) refers to the association of hypogonadic hypogonadism and anosmia or hyposmia. The X-linked form of the disease is due to mutations in the KAL1 gene that encodes for the protein anosmin-1. We studied the KAL1 gene in a patient with KS and his family by PCR amplification and direct sequencing. A novel missense mutation (V263G) that modifies the major cell adhesion site of the anosmin-1 protein was identified. Our results suggest that this reported mutation is responsible for KS and might help to elucidate the function of an important area of the anosmin-1 protein.

Changes in Body Mass Index in Girls with Idiopathic Central Precocious Puberty under Gonadotropin-Releasing Hormone Analogue Therapy: The Spanish Registry

Background: The influence of gonadotropin-releasing hormone analogue (GnRHa) treatment on body mass index (BMI) evolution in girls with idiopathic central precocious puberty (CPP) is unclear. Hence, we aimed to evaluate the effect of GnRHa treatment on BMI-standard deviation score (SDS) from diagnosis of idiopathic CPP until adult height. Methods: An observational study of girls diagnosed with CPP in Spain was carried out between January 2008 and December 2014. A computer program was designed to process clinical and biological data from patients treated in 55 departments of pediatric endocrinology throughout the country. The inclusion criteria were (1) girls diagnosed with CPP before 8 years of age; (2) born after 1992; (3) with a difference between bone and chronological age of at least 1 year, and (4) with a luteinizing hormone peak >7 U/l during luteinizing hormone-releasing hormone testing. The influence of GnRHa treatment on BMI-SDS evolution was analyzed. Results: Data from 333 girls (22.2% adopted) were evaluated. We report follow-up data at 6, 12, 24, 36, 48 and 60 months and adult height from 269, 232, 198, 153, 105, 56 and 49 girls, respectively. During treatment, there was an increase in BMI-SDS of 0.43 ± 1.17 (95% CI: 0.20-0.64). At adult height (n = 49), BMI-SDS was 1.51 ± 1.38, which was 0.60 ± 1.09 higher than at diagnosis (95% CI: 0.43-0.75). Conclusions: During treatment with GnRHa, girls experience a significant increase in BMI-SDS that persists after therapy is stopped and adult height has been reached.

Precocious presentation of autoimmune polyglandular syndrome type 2 associated with an AIRE mutation

Autoimmune polyglandular syndrome type 2 (type 2 APS), or Schmidt’s syndrome, is defined by the presence of Addison’s disease in combination with type 1 diabetes and/or autoimmune thyroid disease. The estimated prevalence of this syndrome is 1.4–4.5 per 100,000 inhabitants and it is more frequent in middle-aged females, whilst it is quite rare in children. Type 2 APS, which shows a pattern of autosomal dominant inheritance with low penetrance, has been associated with HLA specific DR3/DQ2 and DR4/DQ8 haplotypes. However, it has been hypothesized that genetic variability in the AIRE gene, which causing type 1 APS, may play a role in more common organ-specific autoimmune conditions like type 1 diabetes, Hashimoto’s disease and type 2 APS, among others. Here we present the case of an 8-year-old girl, with a past medical history of type 1 diabetes diagnosed at the age of 3. She was taken to the Emergency Department because she complained of abdominal pain, nausea and vomiting, and her blood analysis revealed a severe hyponatremia. She also had seizures as a consequence of the hyponatremia and frequent hypoglycemia. She was ultimately found to be suffering from autoimmune primary adrenal insufficiency. The combination of both mentioned conditions, type 1 diabetes and Addison’s disease, in the absence of chronic mucocutaneous candidiasis, made a diagnosis of type 2 APS plausible in this girl. The genetic study showed two heterozygous variants: NM_000383.2:C.1411C>T (p. Arg471Cys) in exon 12 and IVS9+6G>A in intron 9 of the AIRE gene. The description of an uncommon case of type 2 APS with precocious presentation associated with an AIRE mutation in a very young girl could help to clarify the role of AIRE in the development of autoimmune diseases.

Severe neurological abnormalities in a young boy with impaired thyroid hormone sensitivity due to a novel mutation in the MCT8 gene

Monocarboxylate transporter 8 (MCT8) is an active and specific thyroid hormone transporter into neurons. MCT8 mutations cause an X-linked condition known as Allan-Herndon-Dudley syndrome and are characterized by impaired psychomotor development and typical abnormal thyroid function. We describe a 10-year-old boy with severe cognitive disability, axial hypotonia, spastic quadriplegia and sporadic dyskinetic episodes. He initially presented with thyroid dysfunction (high FT3, low rT3, low FT4 and normal TSH) and generalized retardation of the cerebral and cerebellar myelination in brain magnetic resonance imaging. The clinical and laboratory findings led to sequencing of the SLC16A2/MCT8 gene, which identified a novel missense mutation in exon 5. The study of peripheral markers of thyroid function suggests a paradoxical state of thyrotoxicosis in some peripheral tissues. Our patient had a typical clinical presentation at birth but because of the rarity of his disease his diagnosis was not made until the age of 7. The delay can also be explained by the omission of the free T3 assay in the first thyroid evaluation performed. This case therefore highlights the possible benefit of including the T3 assay in the study of patients with severe psychomotor disability of unknown etiology, thus eliminating extra costs for unnecessary complementary diagnostic tests.