Pseudohypoparathyroidism

Recurrent small variants in NESP55/NESPAS associated with broad GNAS methylation defects and pseudohypoparathyroidism type 1B

Pseudohypoparathyroidism type 1B (PHP1B) is associated with epigenetic changes in the maternal allele of the imprinted GNAS gene that inhibit expression of the α subunit of Gs (Gsα), thereby leading to parathyroid hormone resistance in renal proximal tubule cells where expression of Gsα from the paternal GNAS allele is normally silent. Although all patients with PHP1B show loss of methylation for the exon A/B differentially methylated region (DMR), some patients with autosomal dominant PHP1B (AD-PHP1B) and most patients with sporadic PHP1B have additional methylation defects that affect the DMRs corresponding to exons XL, AS1, and NESP. Because the genetic defect is unknown in most of these patients, we sought to identify the underlying genetic basis for AD-PHP1B in 2 multigenerational families with broad GNAS methylation defects and negative clinical exomes. Genome sequencing identified small GNAS variants in each family that were also present in unrelated individuals with PHP1B in a replication cohort. Maternal transmission of one GNAS microdeletion showed reduced penetrance in some unaffected patients. Expression of AS transcripts was increased, and NESP was decreased, in cells from affected patients. These results suggest that the small deletion activated AS transcription, leading to methylation of the NESP DMR with consequent inhibition of NESP transcription, and thereby provide a potential mechanism for PHP1B.

gnas Knockdown Induces Obesity and AHO Features in Early Zebrafish Larvae

GNAS (Guanine Nucleotide-Binding Protein, Alpha Stimulating) is a complex gene that encodes the alpha subunit of the stimulatory G protein (Gsα), critical for signaling through various G protein-coupled receptors. Inactivating genetic and epigenetic changes in GNAS, resulting in Gsα deficiency, cause different variants of pseudohypoparathyroidism, which may manifest features of Albright hereditary osteodystrophy (AHO, a syndrome characterized by early-onset obesity and other developmental defects). Recent findings have linked Gsα deficiency with isolated, severe, early-onset obesity, suggesting it as a potential, underrecognized cause of monogenic, non-syndromic obesity. This study was prompted by identifying several GNAS variants of uncertain significance (VUSs) in pediatric patients presenting with unexplained, severe, early-onset obesity at Sidra Medicine in Qatar. To functionally characterize these variants, we developed the first zebrafish model of Gsα deficiency, offering numerous advantages over other model systems. This was achieved by knockdown of the ortholog through microinjection of translation-blocking Morpholino antisense oligonucleotides into the yolks of 1-8-cell-stage zebrafish embryos. The morphant larvae displayed an obese phenotype, marked by significantly enlarged yolk sacs, increased neutral lipid accumulation, and reduced metabolic rates, among other developmental abnormalities resembling those in AHO. This zebrafish model lays the foundation for efficient functional characterization of GNAS VUSs and paves the way for enhancing our understanding of Gsα deficiency-associated early-onset obesity.

Pseudohypoparathyroidism leading to bilateral hip fracture: A case report

Pseudohypoparathyroidism (PHP) is a group of disorders characterized by end-organ resistance to parathyroid hormone (PTH), resulting in high serum PTH, low calcium, and high phosphate levels. Among its 5 subtypes, PHP type 1a is the most common and leads to hereditary osteodystrophy, marked by short stature, short metacarpals, and electrolyte abnormalities such as hyperphosphatemia and hypocalcemia, which can cause tetany and seizures. Rarely, PHP patients can experience pathological fractures of long bones. This report discusses a 22-year-old female with PHP who presented with myoclonic seizures and bilateral hip fractures. Initial symptoms included fits, flank pain, and later, leg weakness. Diagnosis was based on clinical history, elevated serum PTH, low calcium, high phosphate, bilateral cataracts, hypothyroidism, basal ganglia calcification, and family history. Treatment began with IV calcium, followed by alfacalcidol, oral calcium, and antibiotics, leading to symptom remission. Hip fractures were managed with a POP cast and later closed reduction. The patient was discharged with calcium and 1,25 dihydroxy Vitamin D supplementation and scheduled for regular follow-up.

Prevalence of hearing loss in pseudohypoparathyroidism

BACKGROUND

The main clinical features of pseudohypoparathyroidism (PHP)/inactivating parathyroid hormone/parathyroid hormone-related protein signaling disorders (iPPSD), including parathyroid hormone (PTH) resistance, brachydactyly and short stature, develop during middle and late childhood. Very few studies have addressed hearing loss in PHP/iPPSD patients, and these studies have yielded widely divergent conclusions. The aim of our study was to assess hearing and determine the predictive factors of hearing loss in patients with PHP/iPPSD.

METHODS

Our retrospective cohort study was conducted between March 2019 and May 2020 in the Otolaryngology Department and the calcium phosphate reference center for rare diseases in Bicêtre Paris-Saclay Hospital, France. We retrospectively collected data from patients with PHP/iPPSDs (age, sex, genetic mutations, height, body mass index (BMI), PTH resistance, presence or absence of ectopic ossifications and brachydactyly). All patients underwent auditory investigations, including tonal and vocal audiometry. The primary outcome was the pure tone average (PTA). The PTA was compared with the norm according to the International Organization for Standardization. Hearing loss was defined as a PTA ≥ 20 db.

RESULTS

The median age of the patients was 15.6 years [9.5, 28.5]. Thirty-six patients were diagnosed with iPPSD2, and eight were diagnosed with iPPSD3. Twenty-six of them (59%) were female. Hearing impairment was confirmed in 17 patients (39%). The mean PTA and the mean SRT of the deaf ears were 40 ± 26 db and 31 ± 14 db. The mean difference in the PTA between the patients and the normal controls was 11.4 db (p = 0.00002). Short stature and the presence of ectopic ossifications were two significant predictive factors of hearing loss (p = 0.009 and p = 0.03, respectively). Sex, BMI, PTH resistance, mutation category and brachydactyly were not associated with an increased risk of hearing loss (p = 0.19, p = 0.41, p = 0.13, p = 0.50, p = 0.19, respectively).

CONCLUSION

Our study confirmed the frequency of hearing loss in patients with PHP/iPPSD disease (prevalence = 39%). A diagnosis of PHP/iPPSD should trigger auditory investigations and follow-up, especially when short stature and/or ectopic ossifications are present.

Root resorptions induced by genetic disorders: A systematic review

OBJECTIVES

Root resorption in permanent teeth is a common pathological process that often follows dental trauma or orthodontic treatment. More rarely, root resorption is a feature of genetic disorders and can help with diagnosis. Thus, the present review aims to determine which genetic disorders could induce pathological root resorptions and thus which mutated genes could be associated with them.

METHODS

We conducted a systematic review following the PRISMA guidelines. Articles describing root resorptions in patients with genetic disorders were included from PubMed, Embase, Web of Science, and Google Scholar. We synthesized the genetic disorder, the type, severity, and extent of the resorptions, as well as the other systemic and oral symptoms and histological features.

RESULTS

The synthetic analysis included 25 studies among 937 identified records. We analyzed 21 case reports, three case series, and one cohort study. Overall, we highlighted 14 different pathologies with described root resorptions. Depending on the pathology, the sites of resorption, their extent, and their severity showed differences.

CONCLUSION

With 14 genetic pathologies suspected to induce root resorptions, our findings are significant and enrich a previous classification. Among them, three metabolic disorders, three calcium-phosphorus metabolism disorders, and osteolysis disorders were identified.

Differentiating monogenic and syndromic obesities from polygenic obesity: Assessment, diagnosis, and management

Background

Obesity is a multifactorial neurohormonal disease that results from dysfunction within energy regulation pathways and is associated with increased morbidity, mortality, and reduced quality of life. The most common form is polygenic obesity, which results from interactions between multiple gene variants and environmental factors. Highly penetrant monogenic and syndromic obesities result from rare genetic variants with minimal environmental influence and can be differentiated from polygenic obesity depending on key symptoms, including hyperphagia; early-onset, severe obesity; and suboptimal responses to nontargeted therapies. Timely diagnosis of monogenic or syndromic obesity is critical to inform management strategies and reduce disease burden. We outline the physiology of weight regulation, role of genetics in obesity, and differentiating characteristics between polygenic and rare genetic obesity to facilitate diagnosis and transition toward targeted therapies.

Methods

In this narrative review, we focused on case reports, case studies, and natural history studies of patients with monogenic and syndromic obesities and clinical trials examining the efficacy, safety, and quality of life impact of nontargeted and targeted therapies in these populations. We also provide comprehensive algorithms for diagnosis of patients with suspected rare genetic causes of obesity.

Results

Patients with monogenic and syndromic obesities commonly present with hyperphagia (ie, pathologic, insatiable hunger) and early-onset, severe obesity, and the presence of hallmark characteristics can inform genetic testing and diagnostic approach. Following diagnosis, specialized care teams can address complex symptoms, and hyperphagia is managed behaviorally. Various pharmacotherapies show promise in these patient populations, including setmelanotide and glucagon-like peptide-1 receptor agonists.

Conclusion

Understanding the pathophysiology and differentiating characteristics of monogenic and syndromic obesities can facilitate diagnosis and management and has led to development of targeted pharmacotherapies with demonstrated efficacy for reducing body weight and hunger in the affected populations.

Induced pluripotent stem cells derived renal tubular cells from a patient with pseudohypoparathyroidism and its response to parathyroid hormone stimulation

INTRODUCTION

Creating induced pluripotent stem cells (iPSCs) from somatic cells of patients with genetic diseases offers a pathway to generate disease-specific iPSCs carrying genetic markers. Differentiating these iPSCs into renal tubular cells can aid in understanding the pathophysiology of rare inherited renal tubular diseases through cellular experiments.

MATERIALS AND METHODS

Two Japanese patients with Pseudohypoparathyroidism (PHP), a 49-year-old woman and a 71-year-old man, were studied. iPSC-derived tubular cells were established from their peripheral blood mononuclear cells (PBMCs). We examined changes in intracellular and extracellular cyclic adenosine monophosphate (cAMP) levels in these cells in response to parathyroid hormone (PTH) stimulation.

RESULTS

Renal tubular cells, differentiated from iPSCs of a healthy control (648A1), showed a PTH-dependent increase in both intracellular and extracellular cAMP levels. However, the renal tubular cells derived from the PHP patients' iPSCs showed inconsistent changes in cAMP levels upon PTH exposure.

CONCLUSION

We successfully created disease-specific iPSCs from PHP patients' PBMCs, differentiated them into tubular cells, and replicated the distinctive response of the disease to PTH in vitro. This approach could enhance our understanding of the pathophysiology of inherited renal tubular diseases and contribute to developing effective treatments.

Hair follicle-resident progenitor cells are a major cellular contributor to heterotopic subcutaneous ossifications in a mouse model of Albright hereditary osteodystrophy

Heterotopic ossifications (HOs) are the pathologic process by which bone inappropriately forms outside of the skeletal system. Despite HOs being a persistent clinical problem in the general population, there are no definitive strategies for their prevention and treatment due to a limited understanding of the cellular and molecular mechanisms contributing to lesion development. One disease in which the development of heterotopic subcutaneous ossifications (SCOs) leads to morbidity is Albright hereditary osteodystrophy (AHO). AHO is caused by heterozygous inactivation of GNAS, the gene that encodes the α-stimulatory subunit (Gαs) of G proteins. Previously, we had shown using our laboratory's AHO mouse model that SCOs develop around hair follicles (HFs). Here we show that SCO formation occurs due to inappropriate expansion and differentiation of HF-resident stem cells into osteoblasts. We also show in AHO patients and mice that Secreted Frizzled Related Protein 2 (SFRP2) expression is upregulated in regions of SCO formation and that elimination of Sfrp2 in male AHO mice exacerbates SCO development. These studies provide key insights into the cellular and molecular mechanisms contributing to SCO development and have implications for potential therapeutic modalities not only for AHO patients but also for patients suffering from HOs with other etiologies.

Pseudohypoparathyroidism Type IB with Subclinical Hypothyroidism: a Pedigree Investigation and Literature Review

Pseudohypoparathyroidism (PHP) is a rare genetic disease characterized by hypocalcemia, hyperphosphatemia, and elevated parathyroid hormone (PTH) in serum. Here, we report a case of a patient with pseudohypoparathyroidism type IB (PHPIB) and subclinical hypothyroidism, analyze the clinical and genetic data of his family members, review the relevant literature, and classify and discuss the pathogenesis and clinical characteristics of each subtype. Finally, we discuss the treatment approach to improve clinicians' understanding of the disease.

Identification of a novel GNAS mutation in a family with pseudohypoparathyroidism type 1A

BACKGROUND

Pseudohypoparathyroidism (PHP) is caused by loss-of-function mutations at the GNAS gene (as in the PHP type 1A; PHP1A), de novo or inherited at heterozygous state, or by epigenetic alterations at the GNAS locus (as in the PHP1B). The condition of PHP refers to a heterogeneous group of disorders that share common clinical and biological features of PTH resistance. Manifestations related to resistance to other hormones are also reported in many patients with PHP, in association with the phenotypic picture of Albright hereditary osteodystrophy characterized by short stature, round facies, subcutaneous ossifications, brachydactyly, mental retardation and, in some subtypes, obesity. The purpose of our study is to report a new mutation in the GNAS gene and to describe the significant phenotypic variability of three sisters with PHP1A bearing the same mutation.

CASE PRESENTATION

We describe the cases of three sisters with PHP1A bearing the same mutation but characterized by a significantly different phenotypic picture at onset and during follow-up in terms of clinical features, auxological pattern and biochemical changes. Clinical exome sequencing revealed a never before described heterozygote mutation in the GNAS gene (NM_000516.5 c.118_139 + 51del) of autosomal dominant maternal transmission in the three siblings, confirming the diagnosis of PHP1A.

CONCLUSIONS

This study reported on a novel mutation of GNAS gene and highlighted the clinical heterogeneity of PHP1A characterized by wide genotype-phenotype variability. The appropriate diagnosis has crucial implications for patient care and long-term multidisciplinary follow-up.

Epileptic seizures and abnormal tooth development as primary presentation of pseudohypoparathyroidism type 1B

Pseudohypoparathyroidism (PHP) is a rare genetic disorder characterised by a non-functioning PTH. Usually, the diagnosis is made following (symptomatic) hypocalcaemia. We describe a case in which epileptic seizures and abnormalities in dental development were the main clinical manifestation of PHP type 1B. This case demonstrates the importance of screening for hypocalcaemia in patients with de novo epileptic seizures. In addition, antiepileptic medications themselves may interfere with calcium-phosphate metabolism, causing or aggravating a hypocalcaemia as well. By correcting the calcium level, a resolution of these symptoms could be obtained.

Clinical and Molecular Characteristics and Long-term Follow-up of Children With Pseudohypoparathyroidism Type IA

CONTEXT

Pseudohypoparathyroidism type IA (PHPIA) is a rare genetic disorder characterized by hormone resistance and a typical phenotype named Albright hereditary osteodystrophy. Unawareness of this rare disease leads to delays in diagnosis.

OBJECTIVE

The aims of this study were to describe the clinical and molecular characteristics of patients with genetically confirmed GNAS mutations and to evaluate their long-term outcomes.

METHODS

A retrospective search for all patients diagnosed with PHPIA in 2 referral centers in Israel was conducted.

RESULTS

Nine children (8 females) belonging to 6 families were included in the study. Five patients had GNAS missense mutations, 2 had deletions, and 2 had frameshift mutations. Four mutations were novel. Patients were referred at a mean age of 2.4 years due to congenital hypothyroidism (5 patients), short stature (2 patients), or obesity (2 patients), with a follow-up duration of up to 20 years. Early obesity was observed in the majority of patients. Elevated parathyroid hormone was documented at a mean age of 3 years; however, hypocalcemia became evident at a mean age of 5.9 years, about 3 years later. All subjects were diagnosed with mild to moderate mental retardation. Female adult height was very short (mean -2.5 SD) and 5 females had primary or secondary amenorrhea.

CONCLUSION

Long-term follow-up of newborns with a combination of congenital hypothyroidism, early-onset obesity, and minor dysmorphic features associated with PHPIA is warranted and molecular analysis is recommended since the complete clinical phenotype may develop a long time after initial presentation.

Pseudohypoparathyroidism: complex disease variants with unfortunate names

Several human disorders are caused by genetic or epigenetic changes involving the GNAS locus on chromosome 20q13.3 that encodes the alpha-subunit of the stimulatory G protein (Gsα) and several splice variants thereof. Thus, pseudohypoparathyroidism type Ia (PHP1A) is caused by heterozygous inactivating mutations involving the maternal GNAS exons 1-13 resulting in characteristic abnormalities referred to as Albright's hereditary osteodystrophy (AHO) that are associated with resistance to several agonist ligands, particularly to parathyroid hormone (PTH), thereby leading to hypocalcemia and hyperphosphatemia. GNAS mutations involving the paternal Gsα exons also cause most of these AHO features, but without evidence for hormonal resistance, hence the term pseudopseudohypoparathyroidism (PPHP). Autosomal dominant pseudohypoparathyroidism type Ib (PHP1B) due to maternal GNAS or STX16 mutations (deletions, duplications, insertions, and inversions) is associated with epigenetic changes at one or several differentially methylated regions (DMRs) within GNAS. Unlike the inactivating Gsα mutations that cause PHP1A and PPHP, hormonal resistance is caused in all PHP1B variants by impaired Gsα expression due to loss of methylation at GNAS exon A/B, which can be associated in some familial cases with epigenetic changes at the other maternal GNAS DMRs. The genetic defect(s) responsible for sporadic PHP1B, the most frequent variant of this disorder, remain(s) unknown for the majority of patients. However, characteristic epigenetic GNAS changes can be readily detected that include a gain of methylation at the neuroendocrine secretory protein (NESP) DMR. Multiple genetic or epigenetic GNAS abnormalities can thus impair Gsα function or expression, consequently leading to inadequate cAMP-dependent signaling events downstream of various Gsα-coupled receptors.

Vara Deformity and Subluxed Humeral Heads: An Unusual Sign in Pseudohypoparathyroidism

Pseudohypoparathyroidism is a rare disorder characterized by end-organ resistance to intact parathyroid hormone (PTH) and concomitant laboratory findings of hypocalcemia and hyperphosphatemia. Radiologic evidence of the disease may manifest as a variety of bone abnormalities. This case describes an 11-year-old female with a history of repaired bilateral slipped capital femoral epiphysis who presented with a limited range of motion of the bilateral upper extremities. Laboratory findings were consistent with pseudohypoparathyroidism. Radiographs revealed subchondral resorption of bilateral clavicular heads and multiple ribs and band lucencies of proximal humeral metaphyses, along with vara deformity and inferior subluxation of the humeral heads. This presentation adds to the spectrum of potential radiographic manifestations of pseudohypoparathyroidism.

The role of genetic and epigenetic GNAS alterations in the development of early-onset obesity

BACKGROUND

GNAS (guanine nucleotide-binding protein, alpha stimulating) is an imprinted gene that encodes Gsα, the α subunit of the heterotrimeric stimulatory G protein. This subunit mediates the signalling of a diverse array of G protein-coupled receptors (GPCRs), including the melanocortin 4 receptor (MC4R) that serves a pivotal role in regulating food intake, energy homoeostasis, and body weight. Genetic or epigenetic alterations in GNAS are known to cause pseudohypoparathyroidism in its different subtypes and have been recently associated with isolated, early-onset, severe obesity. Given the diverse biological functions that Gsα serves, multiple molecular mechanisms involving various GPCRs, such as MC4R, β2- and β3-adrenoceptors, and corticotropin-releasing hormone receptor, have been implicated in the pathophysiology of severe, early-onset obesity that results from genetic or epigenetic GNAS changes.

SCOPE OF REVIEW

This review examines the structure and function of GNAS and provides an overview of the disorders that are caused by defects in this gene and may feature early-onset obesity. Moreover, it elucidates the potential molecular mechanisms underlying Gsα deficiency-induced early-onset obesity, highlighting some of their implications for the diagnosis, management, and treatment of this complex condition.

MAJOR CONCLUSIONS

Gsα deficiency is an underappreciated cause of early-onset, severe obesity. Therefore, screening children with unexplained, severe obesity for GNAS defects is recommended, to enhance the molecular diagnosis and management of this condition.

Prevalence of Pseudohypoparathyroidism and Nonsurgical Hypoparathyroidism in Japan in 2017: A Nationwide Survey

BACKGROUND

Pseudohypoparathyroidism (PHP) and nonsurgical hypoparathyroidism (NS-HypoPT) are rare diseases with hypocalcemia, hyperphosphatemia, and high and low parathyroid hormone levels, respectively. In Japan, over 20 years have passed since the last survey on these diseases. We carried out a nationwide cross-sectional survey to estimate the prevalence of these diseases in 2018.

METHODS

We conducted a nationwide mail-based survey targeting hospitals in 2018. From a total of 13,156 departments throughout Japan, including internal medicine, pediatrics, neurology, and psychiatry, 3,501 (27%) departments were selected using a stratified random sampling method. We asked each included department to report the number of patients with PHP and NS-HypoPT in 2017.

RESULTS

The overall survey response rate was 52.0% (1,807 departments). The estimated number of patients with PHP and NS-HypoPT was 1,484 (95% confidence interval [CI], 1,143-1,825) and 2,304 (95% CI, 1,189-3,419), respectively; the prevalence per 100,000 population was 1.2 and 1.8, respectively.

CONCLUSION

In this study, we generated estimates of the national prevalence of PHP and NS-HypoPT in Japan during 2017, which were found to be higher than those previously reported.

A Case of Pseudohypoparathyroidism Misdiagnosed as Idiopathic Epilepsy for 5 Years: Clinical Analysis and Follow-up Outcomes

We report a 15-year-old Chinese girl who presented with intermittent seizure episodes and had been misdiagnosed as having idiopathic epilepsy 5 years previously. Laboratory testing revealed hypocalcemia, hyperphosphatemia, and a high parathyroid hormone (PTH) concentration. She was subsequently shown to have pseudohypoparathyroidism type Ib (PHPIb) based on the results of methylation analysis of the GNAS gene, which showed a loss of methylation of the differentially methylated regions (DMR) of GNAS-AS1, GNAS-XL, and GNAS-A/B; and a gain of methylation of the DMR of the GNAS-NESP55 region. We adjusted the patient's medication by prescribing calcium and calcitriol supplements, and gradually reduced the doses of antiepileptic drugs, until they had been completely discontinued. As a result, the patient did not experience any further seizures or epileptiform symptoms; and had normal plasma calcium, phosphorus, and 25-hydroxyvitamin D concentrations and 24-hour urinary calcium excretion. In addition, her PTH concentration gradually normalized over 12 months, and no urinary stones were found on ultrasonographic examination. In conclusion, the clinical presentation of PHP is complex, and the condition is often misdiagnosed. The diagnosis and follow-up of the present patient have provide valuable insights that should contribute to informed clinical decision-making and the implementation of appropriate treatment strategies.

Neonatal and Early Infancy Features of Patients With Inactivating PTH/PTHrP Signaling Disorders/Pseudohypoparathyroidism

BACKGROUND

Pseudohypoparathyroidism (PHP) and related disorders newly referred to as inactivating PTH/PTHrP signaling disorders (iPPSD) are rare endocrine diseases. Many clinical features including obesity, neurocognitive impairment, brachydactyly, short stature, parathyroid hormone (PTH) resistance, and resistance to other hormones such as thyroid-stimulating hormone (TSH) have been well described, yet they refer mainly to the full development of the disease during late childhood and adulthood.

OBJECTIVE

A significant delay in diagnosis has been reported; therefore, our objective is to increase awareness on neonatal and early infancy presentation of the diseases. To do so, we analyzed a large cohort of iPPSD/PHP patients.

METHODS

We included 136 patients diagnosed with iPPSD/PHP. We retrospectively collected data on birth and investigated the rate of neonatal complications occurring in each iPPSD/PHP category within the first month of life.

RESULTS

Overall 36% of patients presented at least one neonatal complication, far more than the general population; when considering only the patients with iPPSD2/PHP1A, it reached 47% of the patients. Neonatal hypoglycemia and transient respiratory distress appeared significantly frequent in this latter group, ie, 10.5% and 18.4%, respectively. The presence of neonatal features was associated with earlier resistance to TSH (P < 0.001) and with the development of neurocognitive impairment (P = 0.02) or constipation (P = 0.04) later in life.

CONCLUSION

Our findings suggest that iPPSD/PHP and especially iPPSD2/PHP1A newborns require specific care at birth because of an increased risk of neonatal complications. These complications may predict a more severe course of the disease; however, they are unspecific which likely explains the diagnostic delay.

GNAS locus: bone related diseases and mouse models

GNASis a complex locus characterized by multiple transcripts and an imprinting effect. It orchestrates a variety of physiological processes via numerous signaling pathways. Human diseases associated with the GNAS gene encompass fibrous dysplasia (FD), Albright's Hereditary Osteodystrophy (AHO), parathyroid hormone(PTH) resistance, and Progressive Osseous Heteroplasia (POH), among others. To facilitate the study of the GNAS locus and its associated diseases, researchers have developed a range of mouse models. In this review, we will systematically explore the GNAS locus, its related signaling pathways, the bone diseases associated with it, and the mouse models pertinent to these bone diseases.

Recombinant growth hormone improves growth and adult height in patients with maternal inactivating GNAS mutations

BACKGROUND

Maternal inactivating GNAS mutations lead to pseudohypoparathyroidism 1A (PHP1A), newly classified as inactivating parathyroid hormone (PTH)/PTHrP-signaling disorder type 2 of maternal inheritance (iPPSD2). Patients present with resistance to PTH and other hormones, subcutaneous ossifications, brachydactyly, short stature, and early-onset obesity. They can be born small for gestational age (SGA) and may present with growth hormone (GH) deficiency. The use of recombinant human GH (rhGH) therapy has been sporadically reported, yet we lack data on the long-term efficacy and safety of rhGH, as well as on adult height.

OBJECTIVE

Our multicenter, retrospective, observational study describes growth in patients treated with rhGH in comparison with untreated iPPSD2/PHP1A controls.

METHODS

We included 190 patients, of whom 26 received rhGH. Height, weight, body mass index at various time points, and adult height were documented. We analyzed the effect of rhGH on adult height by using linear mixed models.

RESULTS

Adult height was available for 11/26 rhGH-treated individuals and for 69/164 controls. Patients treated with rhGH showed a gain in height of 0.7 standard deviation scores (SDS) after 1 year (CI +0.5 to +0.8, P < .001) and of 1.5 SDS after 3 years (CI +1.0 to +2.0, P < .001). Additionally, there was a clear beneficial impact of rhGH on adult height when compared with untreated controls, with a difference of 1.9 SDS (CI +1.1 to +2.7, P < .001). Body mass index SDS did not vary significantly upon rhGH therapy.

CONCLUSION

Recombinant human growth hormone treatment of iPPSD2/PHP1A patients with short stature improves growth and adult height. More studies are needed to confirm long-term efficacy and safety.

Seudohipoparatiroidismo: enfermedad huérfana en endocrinología. Reporte de un caso

Resumen Introducción. El seudohipoparatiroidismo (SPT) es un trastorno genético poco frecuente que se caracteriza por la resistencia a la hormona paratiroidea (PTH). En Colombia existen pocos reportes sobre esta enfermedad, por lo que la publicación del presente caso contribuye a aumentar el interés en su búsqueda en el ámbito clínico. Presentación del caso. Hombre de 18 años con antecedente de hipotiroidismo (diagnosticado a los 4 meses de nacido), retraso del crecimiento, desarrollo puberal tardío, obesidad, braquidactilia, fracturas patológicas, osteocondroma femoral, insomnio, parestesias y estreñimiento crónico, quien asistió al servicio de endocrinología de un hospital de tercer nivel de Bogotá (Colombia) remitido luego de haber estado hospitalizado por un episodio convulsivo. En dicha hospitalización los laboratorios evidenciaron hipocalcemia, hiperfosfatemia y 25-OH vitamina D en rango de insuficiencia con niveles elevados de PTH, y los estudios imagenológicos demostraron osificaciones heterotópicas y calcificaciones de ganglios basales del cerebro. Al paciente se le realizó un estudio genético que confirmó el diagnóstico de SPT1A, por lo que se le inició manejo con suplencia de calcio, colecalciferol y quelantes de fósforo, con lo cual evolucionó satisfactoriamente. Tanto el paciente como sus familiares de primer grado recibieron asesoramiento y valoración interdisciplinaria. Conclusiones. El SPT1A es un trastorno genético complejo poco conocido pero de alta importancia clínica dentro de los diagnósticos diferenciales de hipocalcemia que debe considerarse ya que sin el diagnóstico y tratamiento oportunos, los pacientes pueden presentar consecuencias metabólicas graves y potencialmente fatales.

Short stature in PRMT7 Mutations: first evidence of response to growth hormone treatment

Protein arginine methyltransferase 7 (PRMT7) pathogenetic variants have been associated with the human disorder of Short Stature, Brachydactyly, Intellectual Developmental Disability and Seizures syndrome (SBIDDS). Only 15 cases have been described in the literature. Here we report two female dizygotic twins with novel compound heterozygous deleterious variants of PRMT7 and describe the associated endocrine manifestations and short-term response to recombinant growth hormone (rGH) treatment. They were born at 36 + 3 weeks from a dichorionic diamniotic twin pregnancy. Twin A was appropriate for gestational age while Twin B was small for gestational age. Whole exome sequencing analyses showed the same novel compound heterozygous genetic defects in the PRMT7 gene (c.1220 G > A of maternal origin; c.1323 + 2 T > G of paternal origin, Fig. 1). Due to severe short stature and growth impairment, at six years of age, endocrine investigations were performed to rule out growth hormone (GH) deficiency, and revealed GH deficiency (GHD) in Twin A and an appropriate GH response in Twin B. Therefore, both started rGH, albeit at different dosages according to the underlying diagnosis. Both showed a satisfactory short-term response to treatment with height gain (∆HT) of +0.52 SDS (Twin A) and +0.88 SDS (Twin B) during the first year. In conclusion, our findings expand the knowledge about the endocrine manifestations associated with PRMT7 pathogenetic variants, including GH deficiency and rGH response. Further studies are needed to investigate long-term outcomes and establish whether PRMT7 genetic defects can be included among syndromic short stature treatable with rGH.

Prevalence of Chiari malformation type 1 is increased in pseudohypoparathyroidism type 1A and associated with aberrant bone development

BACKGROUND

Albright hereditary osteodystrophy (AHO) is caused by heterozygous inactivating mutations in GNAS. Patients with maternally-inherited mutations develop pseudohypoparathyroidism type 1A (PHP1A) with multi-hormone resistance and aberrant craniofacial and skeletal development among other abnormalities. Chiari malformation type 1 (CM1), a condition in which brain tissue extends into the spinal canal when the skull is too small, has been reported in isolated cases of PHP1A. It has been hypothesized to be associated with growth hormone (GH) deficiency. Given the adverse clinical sequelae that can occur if CM1 goes unrecognized, we investigated the previously undetermined prevalence of CM1, as well as any potential correlations with GH status, given the known increased prevalence of GH deficiency in PHP1A. We also investigated these metrics for low lying cerebellar tonsils (LLCT), defined as tonsillar descent less than 5 mm below the foramen magnum. In addition, we investigated possible correlations of CM1/LLCT with advanced hand/wrist bone ages and craniofacial abnormalities known to occur in PHP1A to determine whether premature chondrocyte differentiation and/or aberrant craniofacial development could be potential etiologies of CM1/LLCT through both human studies and investigations of our AHO mouse model.

METHODS

We examined patients with PHP1A in our clinic and noticed CM1 more frequently than expected. Therefore, we set out to determine the true prevalence of CM1 and LLCT in a cohort of 54 mutation-confirmed PHP1A participants who had clinically-indicated brain imaging. We examined potential correlations with GH status, clinical features, biological sex, genotype, and hand/wrist bone age determinations. In addition, we investigated the craniofacial development in our mouse model of AHO (Gnas E1+/-m) by histologic analyses, dynamic histomorphometry, and micro-computerized tomographic imaging (MCT) in order to determine potential etiologies of CM1/LLCT in PHP1A.

RESULTS

In our cohort of PHP1A, the prevalence of CM1 is 10.8%, which is at least 10-fold higher than in the general population. If LLCT is included, the prevalence increases to 21.7%. We found no correlation with GH status, biological sex, genotype, or hand/wrist bone age. Through investigations of our Gnas E1+/-m mice, the correlate to PHP1A, we identified a smaller cranial vault and increased cranial dome angle with evidence of hyperostosis due to increased osteogenesis. We also demonstrated that there was premature closure of the spheno-occipital synchondrosis (SOS), a cartilaginous structure essential to the development of the cranial base. These findings lead to craniofacial abnormalities and could contribute to CM1 and LLCT development in PHP1A.

CONCLUSION

The prevalence of CM1 is at least 10-fold higher in PHP1A compared to the general population and 20-fold higher when including LLCT. This is independent of the GH deficiency that is found in approximately two-thirds of patients with PHP1A. In light of potential serious consequences of CM1, clinicians should have a low threshold for brain imaging. Investigations of our AHO mouse model revealed aberrant cranial formation including a smaller cranium, increased cranial dome angle, hyperostosis, and premature SOS closure rates, providing a potential etiology for the increased prevalence of CM1 and LLCT in PHP1A.

Central Precocious Puberty in a Boy with Pseudohypoparathyroidism Type 1A due to a Novel GNAS Variant, with Congenital Hypothyroidism as the First Manifestation

Pseudohypoparathyroidism (PHP) type 1A (PHP1A) is a disorder of multiple hormone resistance, mainly parathyroid hormone. It is associated with Albright hereditary osteodystrophy phenotypes. Patients with PHP1A may initially present with hypothyroidism during infancy and later develop typical PHP1A characteristics during their childhood. Central precocious puberty (CPP) is extremely rare among PHP1A patients in whom gonadotropin resistance is more usual. This is a case report of a 9.5-year-old boy with congenital hypothyroidism who developed hypocalcemia secondary to PHP. He had relatively short stature with height standard deviation score of -0.9. Obesity had been noted since the age of two years. At the presentation of PHP, pubertal-sized testes of 10 mL were observed, and CPP was documented with serum testosterone concentration of 298 ng/dL (normal for Tanner stage III, 100-320), luteinizing hormone of 3.9 IU/L (normal, 0.2-5.0), and follicle stimulating hormone of 4.8 IU/L (normal, 1.2-5.8). Pituitary magnetic resonance imaging was unremarkable. Genetic analysis confirmed the diagnosis of PHP1A with a novel heterozygous missense variant of GNAS gene in exon 13, c.1103A>G (p.Asp368Gly). Awareness of PHP1A diagnosis in patients with congenital hypothyroidism and early childhood-onset obesity is important for early diagnosis. Apart from multiple hormone resistance, CPP may manifest in patients with PHP1A.

Pathogenic variants of the GNAS gene introduce an abnormal amino acid sequence in the β6 strand/α5 helix of Gsα, causing pseudohypoparathyroidism type 1A and pseudopseudohypoparathyroidism in two unrelated Japanese families

Pseudohypoparathyroidism 1A (PHP1A) and pseudopseudohypoparathyroidism (PPHP) are caused by loss-of-function variants of GNAS, which encodes Gsα. We present two unrelated Japanese families with PHP1A and PPHP harboring unreported pathogenic variants of GNAS (c.1141delG, p.Asp381Thrfs*23 and c.1117delC, p.Arg373Alafs*31). These variants introduce abnormal amino acids in the β6 strand/α5 helix of Gsα, which interact with G protein coupling receptor (GPCR). We conclude that these variants alter the association of Gsα with GPCR and cause PHP1A or PPHP.

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Reports of GNAS variants causing extra amino acid sequences are limited.

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Two cases with extended Gsα mutants showed clinical characteristics of PHP1A/PPHP.

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No change was found in the affinity between mutant Gsα and GDP using I-TASSER.

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I-TASSER and AlphaFold2 suggested the Gsα mutants caused dysfunction with GPCR.

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Prediction by I-TASSER and AlphaFold2 are useful in determination of pathogenicity.

Clinical and genetic characteristics for 4 patients with Type Ib pseudohypoparathyroidism

Pseudohypoparayhyroidism (PHP) is a rare autosomal dominant or recessive genetic disorder characterized by low calcium, high phosphorus, and target organ resistance to parathyroid. The clinical characteristics and genetic features in 4 patients with Type Ib PHP in the Third Xiangya Hospital, Central South University, have been reviewed. All 4 patients had low calcium, high phosphorus, and parathyroid resistance. Among them, 2 patients had slightly elevated thyroid stimulating hormone and mild features of Albright's hereditary osteodystrophy, and one patient had hypokalemia. No guanine nucleotide-binding protein alpha-stimulating activity polypeptide 1 (GNAS) and gene variant associated with hypokalemia were identified using the whole exome sequencing. The results of the methylation-specific multiple ligation-dependent probe amplification showed that there were abnormal methylation of the upstream differentially methylated regions of GNAS in the 4 patients. There were phenotype overlap among the various subtypes of PHP. Detection of GNAS gene methylation in patients with clinical suspicion of Type Ib PHP is helpful for the diagnosis and treatment of PHP.

PTH, FGF-23, Klotho and Vitamin D as regulators of calcium and phosphorus: Genetics, epigenetics and beyond

The actions of several bone-mineral ion regulators, namely PTH, FGF23, Klotho and 1,25(OH)2 vitamin D (1,25(OH)2D), control calcium and phosphate metabolism, and each of these molecules has additional biological effects related to cell signaling, metabolism and ultimately survival. Therefore, these factors are tightly regulated at various levels - genetic, epigenetic, protein secretion and cleavage. We review the main determinants of mineral homeostasis including well-established genetic and post-translational regulators and bring attention to the epigenetic mechanisms that affect the function of PTH, FGF23/Klotho and 1,25(OH)2D. Clinically relevant epigenetic mechanisms include methylation of cytosine at CpG-rich islands, histone deacetylation and micro-RNA interference. For example, sporadic pseudohypoparathyroidism type 1B (PHP1B), a disease characterized by resistance to PTH actions due to blunted intracellular cAMP signaling at the PTH/PTHrP receptor, is associated with abnormal methylation at the GNAS locus, thereby leading to reduced expression of the stimulatory G protein α-subunit (Gsα). Post-translational regulation is critical for the function of FGF-23 and such modifications include glycosylation and phosphorylation, which regulate the cleavage of FGF-23 and hence the proportion of available FGF-23 that is biologically active. While there is extensive data on how 1,25(OH)2D and the vitamin D receptor (VDR) regulate other genes, much more needs to be learned about their regulation. Reduced VDR expression or VDR mutations are the cause of rickets and are thought to contribute to different disorders. Epigenetic changes, such as increased methylation of the VDR resulting in decreased expression are associated with several cancers and infections. Genetic and epigenetic determinants play crucial roles in the function of mineral factors and their disorders lead to different diseases related to bone and beyond.

A patient with pseudohypoparathyroidism type 1A previously misdiagnosed as hereditary multiple exostosis: A case report

Pseudohypoparathyroidism type 1A (PHP1A), a rare hereditary disorder, is featured by end-organ resistance to parathyroid hormone and Albright's hereditary osteodystrophy. Heterozygous mutation of guanine nucleotide-binding protein α stimulating (GNAS) gene causes the half decreased bioactivity of the Gsα protein levels. Due to the diverse early clinical manifestations of PHP1A, a diagnosis of PHP1A is often easily overlooked and misdiagnosis or missed diagnosis is common. The present study described a girl who was initially diagnosed with hereditary multiple exostoses, but was afterwards confirmed with PHP1A. Moreover, genetic analysis indicated a new mutation (c2277deIC) of the gene.

The Interaction of Obesity and Reproductive Function in Adolescents

Obesity is increasing worldwide, including in pediatrics. Adequate nutrition is required for initiation of menses, and there is a clear secular trend toward earlier pubertal onset and menarche in females in countries around the globe. Similar findings of earlier pubertal start are suggested in males. However, as individuals and populations have crossed into over-nutritional states including overweight and obesity, the effect of excess weight on disrupting reproductive function has become apparent. Hypothalamic hypogonadism and polycystic ovary syndrome are two conditions where reproductive function appears to directly relate to excess weight. Clinical findings in individuals with certain polygenic and monogenic obesity syndromes, which also have reproductive disruptions, have helped elucidate neurologic pathways that are common to both. Clinical endocrinopathies such as hypothyroidism or panhypopituitarism also aide in the understanding of the role of the endocrine system in weight gain. Understanding the intersection of obesity and reproductive function may lead to future therapies which can treat both conditions.

Hypocalcemia as the Initial Presentation of Type 2 Bartter Syndrome: A Family Report

CONTEXT

Bartter syndrome (BS) is a group of rare autosomal-recessive tubulopathies characterized by hypokalemic, hypochloremic metabolic alkalosis in which the primary defect is a deficiency of transporters involved in sodium chloride reabsorption. Type 2 BS results from a defect in the renal outer medullary potassium channel encoded by the KCNJ1 gene. Type 2 BS presents with polyhydramnios, intrauterine growth retardation, prematurity, failure to thrive, polyuria, hypercalciuria, and life-threatening episodes of dehydration. Hypocalcemia is a very rare presenting symptom of BS, with only a few published cases reporting it as the initial manifestation of type 2 BS.

OBJECTIVE

To describe a child who presented with hypocalcemic seizure at the age of 2.3 years that was first related to vitamin D deficiency and high-phosphate soft drink consumption.

METHODS

Whole exome sequencing (WES) was used to evaluate the biochemical abnormalities of the proband.

RESULTS

We identified a previously described homozygous missense mutation c.212C>T, p.T71M in the KCNJ1 gene associated with type 2 BS. Six additional family members with the same mutation and diagnosed clinically with BS are also reported, 2 presenting with hypocalcemia associated with vitamin D deficiency.

CONCLUSION

This report expands the clinical spectrum associated with KCNJ1 mutations and emphasizes the role of WES in unsolved cases of hypocalcemia when genetic disease is suspected. It also highlights the hazardous effects of phosphate-containing soft drinks on calcium metabolism.

A complex pheotype in a girl with a novel heterozygous missense variant (p.Ile56Phe) of the GNAS gene

BACKGROUND

GNAS is a complex gene that encodes Gsα, a signaling protein that triggers a complex network of pathways. Heterozygous inactivating mutations in Gsα-coding GNAS exons cause hormonal resistance; on the contrary, activating mutations in Gsα result in constitutive cAMP stimulation. Recent research has described a clinical condition characterized by both gain and loss of Gsα function, due to a heterozygous de novo variant of the maternal GNAS allele.

PATIENTS AND METHODS

We describe a girl with a complex combination of clinical signs and a new heterozygous GNAS variant. For the molecular analysis of GNAS gene, DNA samples of the proband and her parents were extracted from their peripheral blood samples. In silico analysis was performed to predict the possible in vivo effect of the detected novel genetic variant. The activity of Gsα protein was in vitro analyzed from samples of erythrocyte membranes, recovered from heparinized blood samples.

RESULTS

We found a new heterozygous missense c.166A > T-(p.Ile56Phe) GNAS variant in exon 2, inherited from the mother that determined a reduced activity of 50% of Gsα protein function. The analysis of her parents showed a 20-25% reduction in Gsα protein activity in the mother and a normal function in the father. Clinically our patient presented a multisystemic disorder characterized by hyponatremia compatible with a nephrogenic syndrome of inappropriate antidiuresis, subclinical hyperthyroidism, subclinical hypercortisolism, precocious thelarche and pubarche and congenital bone abnormalities.

CONCLUSIONS

This is the first time that the new variant c.166A > T (p.Ile56Phe) on exon 2 of GNAS gene, originated on maternal allele, has been described as probable cause of a multisystemic disorder. Although the mutation is associated with a reduced activity of the function of Gsα protein, this unusual phenotype on the contrary suggests a mild functional gain.

Aberrant Bone Regulation in Albright Hereditary Osteodystrophy dueto Gnas Inactivation: Mechanisms and Translational Implications

PURPOSE OF REVIEW

This review highlights the impact of Gnas inactivation on both bone remodeling and the development of heterotopic subcutaneous ossifications in Albright hereditary osteodystrophy (AHO). Here we discuss recent advancements in understanding the pathophysiologic mechanisms of the aberrant bone development in AHO as well as potential translational implications.

RECENT FINDINGS

Gnas inactivation can regulate the differentiation and function of not only osteoblasts but also osteoclasts and osteocytes. Investigations utilizing a mouse model of AHO generated by targeted disruption of Gnas have revealed that bone formation and resorption are differentially affected based upon the parental origin of the Gnas mutation. Data suggest that Gnas inactivation leads to heterotopic bone formation within subcutaneous tissue by changing the connective tissue microenvironment, thereby promoting osteogenic differentiation of tissue-resident mesenchymal progenitors. Observed variations in bone formation and resorption based upon the parental origin of the Gnas mutation warrant future investigations and may have implications in the management and treatment of AHO and related conditions. Additionally, studies of heterotopic bone formation due to Gnas inactivation have identified an essential role of sonic hedgehog signaling, which could have therapeutic implications not only for AHO and related conditions but also for heterotopic bone formation in a wide variety of settings in which aberrant bone formation is a cause of significant morbidity.

Pseudohypoparathyroidism: a diagnosis to consider once a PTH elevation is detected

BACKGROUND AND AIM

Pseudohypoparathyroidism (PHP) is a rare disease, which can occur in the youth, characterized by hypocalcemia and hyperphosphatemia due to resistance to parathyroid hormone (PTH) in target organs. This condition encompasses different conditions which differ between one another by different clinical, biochemically, and genetic features.

METHODS

Herein we report the clinical history of a boy with PHP1B with an interesting clinical presentation. He came in fact to the attention of the Emergency Department because of a spontaneously resolving epileptic attack, lasting about 15 minutes, characterized by loss of consciousness, fall to the ground, tonic-clonic shocks, and sphincter release. Moreover, the personal history was characterized by congenital long QT syndrome (LQTS), with a documented mutation of the KCNQ1 gene, treated with beta-blockers (nadolol).

RESULTS

The simultaneous presence of symptomatic acute hypocalcemia and long QT syndrome undoubtedly required particular attention both in the management of the onset and in the more in-depth subsequent diagnostics. In this regard, laboratory tests and molecular analyzes have proved to be crucial in the diagnostic process. Conclusions: this case underlines the diagnostic path complexity in patients with PTH elevation and the importance of considering all the possible differential diagnoses in order to undertake a timely and correct course of treatment.

New insights into thyroid dysfunction in patients with inactivating parathyroid hormone/parathyroid hormone-related protein signalling disorder (the hormonal and ultrasound aspects): One-centre preliminary results

OBJECTIVE

This study aimed to present the spectrum of thyroid dysfunction, including hormonal and ultrasound aspects, in a cohort of paediatric and adult patients diagnosed with inactivating parathyroid hormone (PTH)/PTH-related protein signalling disorders 2 and 3 (iPPSD).

METHODS

The medical records of 31 patients from 14 families diagnosed with iPPSD between 1980 and 2021 in a single tertiary unit were retrospectively analysed. Biochemical, hormonal, molecular, and ultrasonographic parameters were assessed.

RESULTS

In total, 28 patients from 13 families were diagnosed with iPPSD2 (previously pseudohypoparathyroidism [PHP], PHP1A, and pseudo-PHP) at a mean age of 12.2 years (ranging from infancy to 48 years), and three patients from one family were diagnosed with iPPSD3 (PHP1B). Thyroid dysfunction was diagnosed in 21 of the 28 (75%) patients with iPPSD2. Neonatal screening detected congenital hypothyroidism (CH) in 4 of the 20 (20%) newborns. The spectrum of thyroid dysfunction included: CH, 3/21 (14.2%); CH and autoimmune thyroiditis with nodular goitre, 1/21 (4.8%); subclinical hypothyroidism, 10/21 (47.6%); subclinical hypothyroidism and nodular goitre, 1/21 (4.8%); primary hypothyroidism, 4/21 (19%); and autoimmune thyroiditis (Hashimoto and Graves' disease), 2/21 (9.6%). Thyroid function was normal in 7 of the 28 (25%) patients with iPPSD2 and in all patients with iPPSD3. Ultrasound evaluation of the thyroid gland revealed markedly inhomogeneous echogenicity and structure in all patients with thyroid dysfunction. Goitre was found in three patients.

CONCLUSION

The spectrum of thyroid dysfunction in iPPSD ranges from CH to autoimmune thyroiditis and nodular goitre. Ultrasonography of the thyroid gland may reveal an abnormal thyroid parenchyma.

Parental Origin of Gsα Inactivation Differentially Affects Bone Remodeling in a Mouse Model of Albright Hereditary Osteodystrophy

Albright hereditary osteodystrophy (AHO) is caused by heterozygous inactivation of GNAS, a complex locus that encodes the alpha‐stimulatory subunit of heterotrimeric G proteins (Gsα) in addition to NESP55 and XLαs due to alternative first exons. AHO skeletal manifestations include brachydactyly, brachymetacarpia, compromised adult stature, and subcutaneous ossifications. AHO patients with maternally‐inherited GNAS mutations develop pseudohypoparathyroidism type 1A (PHP1A) with resistance to multiple hormones that mediate their actions through G protein‐coupled receptors (GPCRs) requiring Gsα (eg, parathyroid hormone [PTH], thyroid‐stimulating hormone [TSH], growth hormone–releasing hormone [GHRH], calcitonin) and severe obesity. Paternally‐inherited GNAS mutations cause pseudopseudohypoparathyroidism (PPHP), in which patients have AHO skeletal features but do not develop hormonal resistance or marked obesity. These differences between PHP1A and PPHP are caused by tissue‐specific reduction of paternal Gsα expression. Previous reports in mice have shown loss of Gsα causes osteopenia due to impaired osteoblast number and function and suggest that AHO patients could display evidence of reduced bone mineral density (BMD). However, we previously demonstrated PHP1A patients display normal‐increased BMD measurements without any correlation to body mass index or serum PTH. Due to these observed differences between PHP1A and PPHP, we utilized our laboratory's AHO mouse model to address whether Gsα heterozygous inactivation differentially affects bone remodeling based on the parental inheritance of the mutation. We identified fundamental distinctions in bone remodeling between mice with paternally‐inherited (GnasE1+/−p) versus maternally‐inherited (GnasE1+/−m) mutations, and these findings were observed predominantly in female mice. Specifically, GnasE1+/−p mice exhibited reduced bone parameters due to impaired bone formation and enhanced bone resorption. GnasE1+/−m mice, however, displayed enhanced bone parameters due to both increased osteoblast activity and normal bone resorption. These in vivo distinctions in bone remodeling between GnasE1+/−p and GnasE1+/−m mice could potentially be related to changes in the bone microenvironment driven by calcitonin‐resistance within GnasE1+/−m osteoclasts. Further studies are warranted to assess how Gsα influences osteoblast–osteoclast coupling. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

High-throughput Molecular Analysis of Pseudohypoparathyroidism 1b Patients Reveals Novel Genetic and Epigenetic Defects

CONTEXT

Patients with pseudohypoparathyroidism type 1b (PHP1b) show disordered imprinting of the maternal GNAS allele or paternal uniparental disomy (UPD). Genetic deletions in STX16 or in upstream exons of GNAS are present in many familial but not sporadic cases.

OBJECTIVE

Characterization of epigenetic and genetic defects in patients with PHP1b.

DESIGN AND PATIENTS

DNA from 84 subjects, including 26 subjects with sporadic PHP1b, 27 affected subjects and 17 unaffected and/or obligate gene carriers from 12 PHP1b families, 11 healthy individuals, and 3 subjects with PHP1a was subjected to quantitative pyrosequencing of GNAS differentially methylated regions (DMRs), microarray analysis, and microsatellite haplotype analysis.

SETTING

Academic medical center.

MAIN OUTCOME MEASUREMENTS

Molecular pathology of PHP1b.

RESULTS

Healthy subjects, unaffected family members and obligate carriers of paternal PHP1b alleles, and subjects with PHP1a showed normal methylation of all DMRs. All PHP1b subjects showed loss of methylation (LOM) at the exon A/B DMR. Affected members of 9 PHP1b kindreds showed LOM only at the exon A/B DMR, which was associated with a 3-kb deletion of STX16 exons 4 through 6 in 7 families and a novel deletion of STX16 and adjacent NEPEPL1 in 1 family. A novel NESP deletion was found in 1 of 2 other families with more extensive methylation defects. One sporadic PHP1b had UPD of 20q, 2 had 3-kb STX16 deletions, and 5 had apparent epigenetic mosaicism.

CONCLUSIONS

We found diverse patterns of defective methylation and identified novel or previously known mutations in 9 of 12 PHP1b families.

Hormone resistance in children: what primary care physicians need to know

Hormone resistance is defined as a reduced or absence of target tissues responsiveness to a hormone, where the presentation is related to either a relative lack or excess of hormones. Various disorders of hormone resistance were encountered including, Laron syndrome, nephrogenic diabetes insipidus, thyroid hormone resistance syndrome, pseudohypoparathyroidism, insulin resistance, familial glucocorticoid deficiency, pseudohypoaldosteronism, X linked hypophosphatemic rickets and androgen insensitivity syndrome. The article gives a summary that presents, in concentrated form, what the primary care physicians need to know about recognition, clinical presentation, diagnosis, and management of various hormone resistance in children.

Osteomyelitis variolosa, an issue inherited from the past: case report and systematic review

Background

Osteomyelitis variolosa is a self-limiting disease triggered by variola virus that cannot be prevented or repaired. Smallpox has been eradicated for 40 years, and complications that remain after smallpox has been cured have become a remarkable diagnostic challenge for contemporary physicians. In this systematic review, we searched PubMed (MEDLINE), Web of Science, and Google Scholar for cases on complications, diagnosis, and treatment for osteomyelitis variolosa between January 1980 and February 2021.

Results

Ten papers and eleven finished cases, all patients from India, were included for comparison with the present case. In total, 100% of patients presented with bilateral elbow deformities, the ankle was the second most common site of lesion in 50%, and knee lesions accounted for 25% in this study. Flexion contracture, joint instability, secondary arthritis, and fracture are common complications of osteomyelitis variolosa, and most patients receive conservative treatment, while internal fixation has good results for combined fractures.

Conclusions

Although osteomyelitis variolosa is not a direct threat to the safety of patients, severe skeletal deformities can have a significant impact on quality of life. With advances in surgical techniques, clinicians are offering an increasing number of treatment options for patients with osteomyelitis variolosa. However, most importantly, smallpox has basically been removed from the historical arena, and for areas where smallpox was once endemic, physicians need to deepen the understanding of this disease again.

Lower Leg Arterial Calcifications Assessed by High-Resolution Peripheral Quantitative Computed Tomography in Hypoparathyroid and Pseudohypoparathyroid Patients

Hypoparathyroidism (HypoPT) and pseudohypoparathyroidism (PHP) are diseases with abnormal calcium and phosphate homeostasis and low and high PTH levels, respectively. It has been hypothesized that this could dispose to vascular calcifications and thereby perhaps also cardiovascular morbidity. The aim of this study was to assess lower leg arterial calcifications (LLAC) in patients with HypoPT or PHP. Using a cross-sectional design, we measured the LLAC using a high-resolution peripheral quantitative computed tomography (HR-pQCT) scanner in 72 patients with HypoPT and 25 patients with PHP and compared them with findings in 61 controls. LLAC were found in only two (3%) of the controls. Compared to the controls, LLAC were significantly more prevalent in patients with HypoPT (N = 12, [17%], p < 0.01) and PHP (N = 4, [16%], p < 0.04). Compared to the patients without calcifications, patients with calcifications had higher plasma calcium levels and a lower eGFR, as well as they were older and more often males. Plasma phosphate levels and the calcium-phosphate product were not associated with LLAC. In conclusion, we found that HypoPT and PHP are associated with an increased prevalence of vascular calcifications.

Snow White and the Seven Dwarfs: a fairytale for endocrinologists

'Snow White and the Seven Dwarfs', a fairytale that is widely known across the Western world, was originally written by the Brothers Grimm, and published in 1812 as 'Snow White'. Though each dwarf was first given an individual name in the 1912 Broadway play, in Walt Disney's 1937 film 'Snow White and the Seven Dwarfs', they were renamed, and the dwarfs have become household names. It is well known that myths, fables, and fairytales, though appearing to be merely children's tales about fictional magical beings and places, have, more often than not, originated from real facts. Therefore, the presence of the seven brothers with short stature in the story is, from an endocrinological point of view, highly intriguing, in fact, thrilling. The diversity of the phenotypes among the seven dwarfs is also stimulating, although puzzling. We undertook a differential diagnosis of their common underlying disorder based on the original Disney production's drawings and the unique characteristics of these little gentlemen, while we additionally evaluated several causes of short stature and, focusing on endocrine disorders that could lead to these clinical features among siblings, we have, we believe, been able to reveal the underlying disease depicted in this archetypal tale.

Preferential Maternal Transmission of STX16-GNAS Mutations Responsible for Autosomal Dominant Pseudohypoparathyroidism Type Ib (PHP1B): Another Example of Transmission Ratio Distortion

Preferential transmission of a genetic mutation to the next generation, referred to as transmission ratio distortion (TRD), is well established for several dominant disorders, but underlying mechanisms remain undefined. Recently, TRD was reported for patients affected by pseudohypoparathyroidism type Ia or pseudopseudohypoparathyroidism. To determine whether TRD is observed also for autosomal dominant pseudohypoparathyroidism type Ib (AD-PHP1B), we analyzed kindreds with the frequent 3-kb STX16 deletion or other STX16/GNAS mutations. If inherited from a female, these genetic defects lead to loss-of-methylation at exon A/B alone or at all three differentially methylated regions (DMR), resulting in parathyroid hormone (PTH)-resistant hypocalcemia and hyperphosphatemia and possibly resistance to other hormones. In total, we investigated 212 children born to 80 females who are unaffected carriers of a STX16/GNAS mutation (n = 47) or affected by PHP1B (n = 33). Of these offspring, 134 (63.2%) had inherited the genetic defect (p = .00012). TRD was indistinguishable for mothers with a STX16/GNAS mutation on their paternal (unaffected carriers) or maternal allele (affected). The mechanisms favoring transmission of the mutant allele remain undefined but are likely to include abnormalities in oocyte maturation. Search for mutations in available descendants of males revealed marginally significant evidence for TRD (p = .038), but these analyses are less reliable because many more offspring of males than females with a STX16/GNAS mutation were lost to follow-up (31 of 98 versus 6 of 218). This difference in follow-up is probably related to the fact that inheritance of a mutation from a male does not have clinical implications, whereas inheritance from an affected or unaffected female results in PHP1B. Lastly, affected PHP1B females had fewer descendants than unaffected carriers, but it remains unclear whether abnormal oocyte development or impaired actions of reproductive hormones are responsible. Our findings highlight previously not recognized aspects of AD-PHP1B that are likely to have implications for genetic testing and counseling. © 2020 American Society for Bone and Mineral Research (ASBMR).

Symptomatic spinal cord compression: an uncommon symptom in pseudohypoparathyroidism

We describe symptomatic spinal cord compression associated with pseudohypoparathyroidism (PHP) in a young female patient and reviewed similar cases previously reported in the literature. The characteristics of these cases were analyzed from etiology, clinical subtypes, symptoms, treatment, and prognosis. Neurological examination revealed functional upper extremities with bilateral lower extremity paraplegia. Laboratory tests showed hypocalcemia, hyperphosphatemia, and elevated parathyroid hormone; high-throughput sequencing showed a heterozygous GNAS mutation in exon 12, specifically c.1006C > T (p.R336W). Imaging findings showed multilevel spinal stenosis with significant spinal cord compression at the T2-T3 level. Seventeen cases with similar characteristics were reviewed. We found that the primary clinical manifestation of these patients was bilateral lower extremity spastic paraplegia. Multilevel spinal cord compression was commonly observed, especially at the lower cervical and upper thoracic spinal cord. Most of the patients had poor surgical treatment outcome and prognosis. Clinicians should be aware of paraplegia due to spinal cord compression as a rare neurological complication in patients with PHP. Early diagnosis and treatment of PHP is one basis for preventing severe spinal cord-related complications.

Gnas Inactivation Alters Subcutaneous Tissues in Progression to Heterotopic Ossification

Heterotopic ossification (HO), the formation of bone outside of the skeleton, occurs in response to severe trauma and in rare genetic diseases such as progressive osseous heteroplasia (POH). In POH, which is caused by inactivation of GNAS, a gene that encodes the alpha stimulatory subunit of G proteins (Gsα), HO typically initiates within subcutaneous soft tissues before progressing to deeper connective tissues. To mimic POH, we used conditional Gnas-null mice which form HO in subcutaneous tissues upon Gnas inactivation. In response to Gnas inactivation, we determined that prior to detection of heterotopic bone, dermal adipose tissue changed dramatically, with progressively decreased adipose tissue volume and increased density of extracellular matrix over time. Upon depletion of the adipose tissue, heterotopic bone progressively formed in those locations. To investigate the potential relevance of the tissue microenvironment for HO formation, we implanted Gnas-null or control mesenchymal progenitor cells into Gnas-null or control host subcutaneous tissues. We found that mutant cells in a Gnas-null tissue environment induced a robust HO response while little/no HO was detected in control hosts. Additionally, a Gnas-null tissue environment appeared to support the recruitment of control cells to heterotopic bone, although control cell implants were associated with less HO formation compared to mutant cells. Our data support that Gnas inactivation alters the tissue microenvironment to influence mutant and wild-type progenitor cells to contribute to HO formation.

Proteomic Profiling Change and Its Implies in the Early Mycosis Fungoides (MF) Using Isobaric Tags for Relative and Absolute Quantification (iTRAQ)

Purpose

Mycosis fungoides (MF) is the most common T-cell lymphoma, with indolent biologic behavior in the early stage and features of invasive in the tumor stage. The diagnosis of MF is still ambiguous and difficult. We focused on the proteomic profiling change in the pathogenesis of early MF and identified candidate biomarkers for early diagnosis.

Methods

We collected peripheral blood samples of MF patients and healthy individuals (HI) performed proteomic profiling analysis using isobaric tags for relative and absolute quantification (iTRAQ) platform. Differently expressed proteins (DEPs) were filtered, and involved biological functions were analyzed through Gene Ontology (GO) and Ingenuity Pathway Analysis (IPA) software.

Results

We identified 78 DEPs including fifty proteins were upregulated and 28 proteins were downregulated in the MF group with HI as a control. Total DEPs were analyzed according to the biological regulation and metabolic process through GO analysis. The pathways of LXR/RXR activation and FXR/RXR activation were significantly activated, in which APOH, CLU, and ITIH4 were involved. The top annotated disease and function network was (Cancer, Organismal Injury and Abnormalities, Reproductive System Disease), with a key node CLU. These DEPs were involved in cancer, including thyroid carcinoma, head and neck carcinoma, and cancer of secretory structure, in which CLU, GNAS, and PKM played an indirect role in the occurrence and development of cancer. Relevant causal network was IL12 (family), which is related to GNAS, PKM, and other DEPs.

Conclusion

Proteomic profiling of early-stage MF provided candidate protein biomarkers such as CLU, GNAS, and PKM, which benefit the early diagnosis and understanding of the mechanism of MF development. Besides, lipid metabolism may be one of the pathogenesis of MF, and IL12 was a potential marker for the diagnosis and treatment of early MF.

Selective pharmacological inhibition of the sodium-dependent phosphate cotransporter NPT2a promotes phosphate excretion

The sodium-phosphate cotransporter NPT2a plays a key role in the reabsorption of filtered phosphate in proximal renal tubules, thereby critically contributing to phosphate homeostasis. Inadequate urinary phosphate excretion can lead to severe hyperphosphatemia as in tumoral calcinosis and chronic kidney disease (CKD). Pharmacological inhibition of NPT2a may therefore represent an attractive approach for treating hyperphosphatemic conditions. The NPT2a-selective small-molecule inhibitor PF-06869206 was previously shown to reduce phosphate uptake in human proximal tubular cells in vitro. Here, we investigated the acute and chronic effects of the inhibitor in rodents and report that administration of PF-06869206 was well tolerated and elicited a dose-dependent increase in fractional phosphate excretion. This phosphaturic effect lowered plasma phosphate levels in WT mice and in rats with CKD due to subtotal nephrectomy. PF-06869206 had no effect on Npt2a-null mice, but promoted phosphate excretion and reduced phosphate levels in normophophatemic mice lacking Npt2c and in hyperphosphatemic mice lacking Fgf23 or Galnt3. In CKD rats, once-daily administration of PF-06869206 for 8 weeks induced an unabated acute phosphaturic and hypophosphatemic effect, but had no statistically significant effect on FGF23 or PTH levels. Selective pharmacological inhibition of NPT2a thus holds promise as a therapeutic option for genetic and acquired hyperphosphatemic disorders.

Diagnosis and management of hypocalcemia

The aim of this clinical narrative review is to summarize and critically appraise the literature on the differential diagnosis of hypocalcemia and to provide its correct management. Calcium is essential for muscle contraction and neurotransmitter release, but clinical manifestations of hypocalcaemia (serum calcium level <8 mg/dl; 2.12 mmol/L) may involve almost any organ and system and may range from asymptomatic to life-threating conditions. Disorders causing hypocalcemia can be divided into parathyroid hormone (PTH) and non-PTH mediated. The most frequent cause of hypocalcemia is postsurgical hypoparathyroidism, while a more comprehensive search for other causes is needed for appropriate treatment in the non PTH-mediated forms. Intravenous calcium infusion is essential to raise calcium levels and resolve or minimize symptoms in the setting of acute hypocalcemia. Oral calcium and/or vitamin D supplementation is the most frequently used as treatment of chronic hypocalcemia. In hypoparathyroidism, providing the missing hormone with the use of the recombinant human (rh) PTH(1-84) has been recently approved both by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA). This new therapy has the advantage of being effective for correcting serum calcium levels and significantly reducing the daily requirements of calcium and active vitamin D supplements. However, due to the high cost, a strict selection of candidates to this therapy is necessary. More challenging is the long-term hypocalcemia treatment, due to its associated complications. The development of long-acting recombinant human PTH will probably modify the management of chronic hypoparathyroidism in the future.