Novel Leptin Receptor Mutations Identified in Two Girls with Severe Obesity Are Associated with Increased Bone Mineral Density

BACKGROUND

Recessive mutations in the leptin receptor (LEPR) are a rare cause of hyperphagia and severe early-onset obesity. To date, the phenotype has only been described in 25 obese children, some of whom also had altered immune function, hypogonadotropic hypogonadism, reduced growth hormone secretion, hypothalamic hypothyroidism or reduced adult height. We provide a detailed description of the phenotype of 2 affected girls to add to this knowledge.

METHODS

Whole-exome sequencing and targeted sequencing were used to detect the LEPR mutations. RNA analysis was performed to assess the effect of splice-site mutations.

RESULTS

In 2 unrelated girls with severe obesity, three novel LEPR mutations were detected. Longitudinal growth data show normal childhood growth, and in the older girl, a normal adult height despite hypogonadotropic hypogonadism and the lack of an obvious pubertal growth spurt. Bone age is remarkably advanced in the younger (prepubertal) girl, and bone mineral density (BMD) is high in both girls, which might be directly or indirectly related to leptin resistance.

CONCLUSION

The spectrum of clinical features of LEPR deficiency may be expanded with increased BMD. Future observations in LEPR-deficient subjects should help further unravel the role of leptin in human bone biology.

The Evaluation and Management of Tall Stature

Tall stature is a common reason for consultation of a paediatric endocrinologist. It is important to always consider underlying pathology. We propose a diagnostic flowchart based on five questions. (1) Does the child have tall stature? (2) Is there evidence of a syndrome? (3) Has there been growth acceleration? (4) Are there signs of puberty? (5) Does the child grow within the target height range? Diagnostic tests can then be ordered targeted to the suspected disorder. The Bayley-Pinneau and Tanner-Whitehouse methods are reasonably accurate in predicting adult height based on bone age in girls, but neither method performs well in boys. Tall stature is not a pathological condition and generally does not need treatment. However, adolescents with a strong treatment wish and their parents should be counselled on the effectivity and safety of available treatments including surgery and high-dose sex steroids. Surgical epiphysiodesis has the advantage that a reasonable height reduction can be achieved at a more advanced bone age, allowing a more accurate adult height prediction to base any treatment decision on. We feel that high-dose oestrogen treatment should no longer be used because of its association with reduced fecundity and imminent ovarian failure.

Birth Weight in Different Etiologies of Disorders of Sex Development

CONTEXT

It is well established that boys are heavier than girls at birth. Although the cause of birth weight (BW) difference is unknown, it has been proposed that it could be generated from prenatal androgen action.

OBJECTIVE

The aim of the current study was to determine the BW of children with disorders of sex development (DSD) of different etiologies and to evaluate the effects of androgen action on BW.

METHODS

Data regarding diagnosis, BW, gestational age, karyotype, and concomitant conditions were collected from the International Disorders of Sex Development (I-DSD) Registry (www.i-dsd). BW standard deviation score was calculated according to gestational age. Cases were evaluated according to disorder classification in I-DSD (i.e., disorders of gonadal development, androgen excess, androgen synthesis, androgen action, nonspecific disorder of undermasculinization groups, and Leydig cell defect).

RESULTS

A total of 533 cases were available; 400 (75%) cases were 46,XY, and 133 (25%) cases were 46,XX. Eighty cases (15%) were born small for gestational age (SGA). Frequency of SGA was higher in the 46,XY group (17.8%) than in the 46,XX (6.7%) group (P = 0.001). Mean BW standard deviation scores of cases with androgen excess and androgen deficiency [in disorders of gonadal development, androgen synthesis, and Leydig cell defect groups and androgen receptor gene (AR) mutation-positive cases in disorders of androgen action groups] were similar to normal children with the same karyotype. SGA birth frequency was higher in the AR mutation-negative cases in disorders of androgen action group and in the nonspecific disorders of the undermasculinization group.

CONCLUSIONS

BW dimorphism is unlikely to be explained by fetal androgen action per se. 46,XY DSDs due to nonspecific disorders of undermasculinization are more frequently associated with fetal growth restriction, SGA, and concomitant conditions.

High predictability of impaired glucose tolerance by combining cardiometabolic screening parameters in obese children

BACKGROUND

There is debate on which overweight and obese children should be screened for the presence of impaired glucose tolerance (IGT) by oral glucose tolerance testing (OGTT). The objective of the study was to identify risk factors predictive of the presence of IGT.

METHODS

In a cohort of overweight children, who underwent OGTT, we determined the association of anthropometric and laboratory parameters with IGT and whether combining parameters improved the sensitivity of screening for IGT.

RESULTS

Out of 145 patients, IGT was present in 11, of whom two had impaired fasting glucose (IFG). Elevated blood pressure (p=0.025) and elevated liver enzymes (p=0.003) were associated with IGT, whereas IFG was not (p=0.067), screening patients with either one of these parameters predicted IGT with a high sensitivity of 1.00, and a number needed to screen of 5.7.

CONCLUSIONS

Screening all patients with either IFG, presence of elevated blood pressure and elevated liver enzymes, significantly increases predictability of IGT compared to using IFG alone.

Perceptions of Sex, Gender, and Puberty Suppression: A Qualitative Analysis of Transgender Youth

International guidelines recommend the use of Gonadotropin-Releasing Hormone (GnRH) agonists in adolescents with gender dysphoria (GD) to suppress puberty. Little is known about the way gender dysphoric adolescents themselves think about this early medical intervention. The purpose of the present study was (1) to explicate the considerations of gender dysphoric adolescents in the Netherlands concerning the use of puberty suppression; (2) to explore whether the considerations of gender dysphoric adolescents differ from those of professionals working in treatment teams, and if so in what sense. This was a qualitative study designed to identify considerations of gender dysphoric adolescents regarding early treatment. All 13 adolescents, except for one, were treated with puberty suppression; five adolescents were trans girls and eight were trans boys. Their ages ranged between 13 and 18 years, with an average age of 16 years and 11 months, and a median age of 17 years and 4 months. Subsequently, the considerations of the adolescents were compared with views of clinicians treating youth with GD. From the interviews with the gender dysphoric adolescents, three themes emerged: (1) the difficulty of determining what is an appropriate lower age limit for starting puberty suppression. Most adolescents found it difficult to define an appropriate age limit and saw it as a dilemma; (2) the lack of data on the long-term effects of puberty suppression. Most adolescents stated that the lack of long-term data did not and would not stop them from wanting puberty suppression; (3) the role of the social context, for which there were two subthemes: (a) increased media-attention, on television, and on the Internet; (b) an imposed stereotype. Some adolescents were positive about the role of the social context, but others raised doubts about it. Compared to clinicians, adolescents were often more cautious in their treatment views. It is important to give voice to gender dysphoric adolescents when discussing the use of puberty suppression in GD. Otherwise, professionals might act based on assumptions about adolescents' opinions instead of their actual considerations. We encourage gathering more qualitative research data from gender dysphoric adolescents in other countries.

Early Medical Treatment of Children and Adolescents With Gender Dysphoria: An Empirical Ethical Study

PURPOSE

The Endocrine Society and the World Professional Association for Transgender Health published guidelines for the treatment of adolescents with gender dysphoria (GD). The guidelines recommend the use of gonadotropin-releasing hormone agonists in adolescence to suppress puberty. However, in actual practice, no consensus exists whether to use these early medical interventions. The aim of this study was to explicate the considerations of proponents and opponents of puberty suppression in GD to move forward the ethical debate.

METHODS

Qualitative study (semi-structured interviews and open-ended questionnaires) to identify considerations of proponents and opponents of early treatment (pediatric endocrinologists, psychologists, psychiatrists, ethicists) of 17 treatment teams worldwide.

RESULTS

Seven themes give rise to different, and even opposing, views on treatment: (1) the (non-)availability of an explanatory model for GD; (2) the nature of GD (normal variation, social construct or [mental] illness); (3) the role of physiological puberty in developing gender identity; (4) the role of comorbidity; (5) possible physical or psychological effects of (refraining from) early medical interventions; (6) child competence and decision making authority; and (7) the role of social context how GD is perceived. Strikingly, the guidelines are debated both for being too liberal and for being too limiting. Nevertheless, many treatment teams using the guidelines are exploring the possibility of lowering the current age limits.

CONCLUSIONS

As long as debate remains on these seven themes and only limited long-term data are available, there will be no consensus on treatment. Therefore, more systematic interdisciplinary and (worldwide) multicenter research is required.

A novel variant of FGFR3 causes proportionate short stature

OBJECTIVE

Mutations of the fibroblast growth factor receptor 3 (FGFR3) cause various forms of short stature, of which the least severe phenotype is hypochondroplasia, mainly characterized by disproportionate short stature. Testing for an FGFR3 mutation is currently not part of routine diagnostic testing in children with short stature without disproportion.

DESIGN

A three-generation family A with dominantly transmitted proportionate short stature was studied by whole-exome sequencing to identify the causal gene mutation. Functional studies and protein modeling studies were performed to confirm the pathogenicity of the mutation found in FGFR3. We performed Sanger sequencing in a second family B with dominant proportionate short stature and identified a rare variant in FGFR3.

METHODS

Exome sequencing and/or Sanger sequencing was performed, followed by functional studies using transfection of the mutant FGFR3 into cultured cells; homology modeling was used to construct a three-dimensional model of the two FGFR3 variants.

RESULTS

A novel p.M528I mutation in FGFR3 was detected in family A, which segregates with short stature and proved to be activating in vitro. In family B, a rare variant (p.F384L) was found in FGFR3, which did not segregate with short stature and showed normal functionality in vitro compared with WT.

CONCLUSIONS

Proportionate short stature can be caused by a mutation in FGFR3. Sequencing of this gene can be considered in patients with short stature, especially when there is an autosomal dominant pattern of inheritance. However, functional studies and segregation studies should be performed before concluding that a variant is pathogenic.

[Maturity-onset diabetes of the young]

Maturity-onset diabetes of the young (MODY) is the most common type of monogenic diabetes mellitus, estimated to account for approximately 1-4% of patients with diabetes. The predicted prevalence is, therefore, 20,000 patients in The Netherlands. Unfortunately less than 5% of these patients are confirmed by molecular genetic analysis. MODY is a clinically heterogeneous group of disorders caused by β-cell dysfunction, which is caused by mutations in multiple genes. MODY is characterized by an early onset of diabetes (often before the age of 30 years) and autosomal dominant inheritance. Patients do not usually require insulin at diagnosis. To emphasize the importance of genetic analysis we describe a 7-year-old boy and his siblings with MODY type 2. Molecular genetic testing is essential for individual patient care, as treatment options differ between the various forms of MODY; it also provides an opportunity to screen relatives.

Ovarian insufficiency and pubertal development after hematopoietic stem cell transplantation in childhood

BACKGROUND

Ovarian insufficiency (OI) and infertility are common and devastating late effects of cancer treatment and hematopoietic stem cell transplantation (HSCT). In children, gonadal insufficiency may subsequently lead to abnormal pubertal development. The aim of this study was to assess the cumulative incidence of OI and the need for hormonal induction of pubertal development after HSCT in childhood. We additionally assessed HSCT-related risk factors for OI.

PROCEDURES

A single center cohort study was undertaken of female patients transplanted during childhood, surviving at least 2 years post-HSCT and who were at least 10 years old at initiation of the study. Of 141 eligible patients, 109 were included and hormone levels and clinical data of these patients during follow-up were collected. Risk factors for OI were analyzed by multivariate Cox regression analysis.

RESULTS

Cumulative incidence of OI was 56% at a median follow-up of 7.2 years. Eight patients, initially diagnosed with OI, showed recovery of ovarian function over time. Hormonal induction of puberty was necessary in 44% of females who were pre-pubertal or pubertal at HSCT. In multivariate analysis, more advanced pubertal stage at HSCT was associated with OI. We found a trend for an association of busulfan with OI in patients conditioned with chemotherapy only.

CONCLUSIONS

The incidence of OI after HSCT was high and associated with more advanced pubertal stage at HSCT. Almost half of the females who were pre-pubertal or pubertal at HSCT required hormonal induction of pubertal development.

An activating mutation in the kinase homology domain of the natriuretic peptide receptor-2 causes extremely tall stature without skeletal deformities

BACKGROUND

C-type natriuretic peptide (CNP)/natriuretic peptide receptor 2 (NPR2) signaling is essential for long bone growth. Enhanced CNP production caused by chromosomal translocations results in tall stature, a Marfanoid phenotype, and skeletal abnormalities. A similar phenotype was described in a family with an activating NPR2 mutation within the guanylyl cyclase domain.

CASE

Here we describe an extremely tall male without skeletal deformities, with a novel NPR2 mutation (p.Arg655Cys) located in the kinase homology domain.

OBJECTIVES

The objective of the study was to investigate the functional and structural effects of the NPR2 mutation.

METHODS

Guanylyl cyclase activities of wild-type vs mutant NPR2 were analyzed in transfected human embryonic kidney 293 cells and in skin fibroblasts. The former were also used to study possible interactions between both isoforms. Homology modeling was performed to understand the molecular impact of the mutation.

RESULTS

CNP-stimulated cGMP production by the mutant NPR2 was markedly increased in patient skin fibroblasts and transfected human embryonic kidney 293 cells. The stimulatory effects of ATP on CNP-dependent guanylyl cyclase activity were augmented, suggesting that this novel mutation enhances both the responsiveness of NPR2 to CNP and its allosteric modulation/stabilization by ATP. Coimmunoprecipitation showed that wild-type and mutant NPR2 can form stable heterodimers, suggesting a dominant-positive effect. In accordance with augmented endogenous receptor activity, plasma N-terminal pro-CNP (a marker of CNP production in tissues) was reduced in the proband.

CONCLUSIONS

We report the first activating mutation within the kinase homology domain of NPR2, resulting in extremely tall stature. Our observations emphasize the important role of this domain in the regulation of guanylyl cyclase activity and bone growth in response to CNP.

Delayed hemolytic transfusion reaction with hyperhemolysis after first red blood cell transfusion in child with beta-thalassemia: challenges in treatment

BACKGROUND

Delayed hemolytic transfusion reaction (DHTR) can manifest with hyperhemolysis, a serious complication of red blood cell (RBC) transfusions. This has mostly been described in sickle cell anemia but occasionally in beta-thalassemia. Treatment is challenging; immunosuppressive medication has been reported to be useful by some but not others.

CASE REPORT

A 1.5-year-old girl with homozygous beta-thalassemia was put on a regular RBC transfusion program because of anemia with stunted growth and abnormal bone development. After the first transfusion she developed DHTR with hyperhemolysis. Further RBC transfusions could not be avoided. Despite treatment with prednisone, immunoglobulins, rituximab, and azathioprine hemolysis continued. She received an allogeneic bone marrow transplantation after conditioning using cyclophosphamide, treosulfan, melfalan, and ATG. The transplantation was followed by treatment with cyclosporin A, methotrexate, and prednisone. Because of poor engraftment and later rejection, she received a retransplantation after conditioning using fludarabine instead of cyclophosphamide and was subsequently treated with prednisone, but hemolysis continued. Only after splenectomy did she no longer need RBC transfusions and the direct antiglobulin test turned negative.

DISCUSSION AND CONCLUSION

Treatment of DHTR remains challenging. The role of immunosuppressive medication such as azathioprine, cyclosporin A, and rituximab remains to be seen. Splenectomy may be helpful. Mainstay is to minimize RBC transfusions as much as possible.

Regulation of Wolffian Duct Development

Wolffian ducts (WDs) are the embryonic structures that form the male internal genitalia. These ducts develop in both the male and female embryo. However, in the female they subsequently regress, whereas in the male they are stabilised by testosterone. The WDs then develop into separate but contiguous organs, the epididymis, vas deferens and seminal vesicles. Recently, considerable progress has been made in identifying genes that are involved in these different stages of development which is described in this review. In addition, WD development in (atypical forms of) cystic fibrosis and intersex disorders, such as the complete androgen insensitivity syndrome, 17beta-hydroxysteroid dehydrogenase deficiency and LH-receptor defects, is discussed. The apparent increase in male reproductive tract disorders is briefly discussed from the perspective of the potential endocrine-disrupting effects of the numerous chemicals in the environment to which the developing male foetus can be exposed.

[Diagnostic image (287). A newborn with exanthema]

A 4-week-old girl presented with annular skin lesions caused by neonatal lupus syndrome.

Changes in Gene Expression during Wolffian Duct Development

BACKGROUND

Wolffian ducts (WDs) are the embryonic precursors of the male reproductive tract. Their development is induced by testosterone, which interacts with the androgen receptor (AR). The molecular pathways underlying androgen-dependent WD development are largely unknown. We aimed to identify AR target genes important in this process.

METHODS

RNA was isolated from rat WDs at E17.5 and E20.5. Affymetrix GeneChip expression arrays were used to identify transcripts up- or downregulated more than 2-fold. Regulation of seven transcripts was confirmed using quantitative PCR.

RESULTS

Transcripts from 76 known genes were regulated, including modulators of insulin-like growth factor and transforming growth factor-beta signalling. By controlling these modulators, androgens may indirectly affect growth factor signalling pathways important in epithelial-mesenchymal interactions and organ development. Caveolin-1, also upregulated, may play a role in modifying as well as mediating AR signalling. Differentiation of WD epithelium and smooth muscle, innervation and extracellular matrix synthesis were reflected in regulation of other transcripts. Several genes were previously suggested to be regulated by androgens or contained functional or putative androgen/glucocorticoid response elements, indicating they may be direct targets of androgen signalling.

CONCLUSION

Our results suggest novel cohorts of signals that may contribute to androgen-dependent WD development and provide hypotheses that can be tested by future studies.

Testicular development in the complete androgen insensitivity syndrome

The complete androgen insensitivity syndrome (CAIS), caused by mutations in the androgen receptor (AR) gene, is associated with abnormal testicular development and an increased risk of germ cell malignancy. Previous histological studies in CAIS have selected patients purely on the basis of clinical diagnosis and were mostly based on small numbers, many of whom were post-pubertal. Here, we present 44 cases of CAIS, each with molecular pathological confirmation of an AR mutation. The median age at gonadectomy was 5.5 years (5.5; IQR 1-13). We have been able, therefore, to investigate testicular development in infancy, childhood and puberty, and estimate the incidence of premalignant change in this series. In addition, we have investigated whether the presence of epididymides and/or vasa deferentia in CAIS, previously shown to be associated with residual activity of mutant ARs, is related to a particular testicular phenotype. Epididymides/vasa deferentia were present in 36% of cases and these patients showed varying degrees of seminiferous tubule maturation at puberty above those without epididymides/vasa deferentia (p = 0.003). There were no other histological differences between these patient groups. In both groups, features of testicular degeneration and dysgenesis were present and germ cell development was delayed, with prolonged expression of the gonocyte markers, placental-like alkaline phosphatase and activator protein-2gamma. Germ cell numbers rapidly declined after the first year of life (R(2) = 0.42). Only two cases of carcinoma in situ were identified in our study and both patients were postpubertal (17 and 53 years). From these results and the literature, we conclude that the risk of premalignant change in germ cells is low before and during puberty. Patients can be advised, therefore, that gonadectomy can be delayed to allow for a natural puberty, with low risk of malignant transformation. Our study only included one patient over 18 years, so we cannot comment on the risk of malignant transformation in later life.

Residual activity of mutant androgen receptors explains wolffian duct development in the complete androgen insensitivity syndrome

Development of the Wolffian ducts (WD) into epididymides and vasa deferentia is dependent on testosterone. Patients with the complete androgen insensitivity syndrome (CAIS) are therefore not expected to develop these structures. However, WD derivatives have been described in cases of CAIS. It is thought that these may be remnants. This study assesses the degree of WD development in 33 patients with CAIS and investigates whether this development was androgen dependent. Epididymides and vasa deferentia were identified in 70% of patients with substitution mutations in the androgen receptor ligand-binding domain. They were more developed than epididymides and vasa deferentia from 16- to 20-wk-old male fetuses, suggesting that the WD had been stimulated to grow, rather than failed to regress. Receptors with substitutions in the ligand-binding domain were normally expressed and showed residual response to androgens in transactivation assays. Patients with premature stop codons or frameshift mutations, which prevented androgen receptor expression, or DNA-binding domain mutations that abolished transcriptional activity did not have epididymides or vasa deferentia. We hypothesize that mutant receptors with residual activity in vitro respond to high local testosterone concentrations in vivo, thereby stimulating WD development. The classification of androgen insensitivity in such patients should be considered severe rather than complete.