Evaluating the variety of GNAS inactivation disorders and their clinical manifestations in 11 Chinese children.

BACKGROUND: The GNAS gene on chromosome 20q13.3, encodes the alpha-subunit of the stimulatory G protein, which is expressed in most tissues and regulated through reciprocal genomic imprinting. Disorders of GNAS inactivation produce several different clinical phenotypes including pseudohypoparathyroidism (PHP), pseudopseudohypoparathyroidism (PPHP), progressive osseous heteroplasia (POH), and osteoma cutis (OC). The clinical and biochemical characteristics overlap of PHP subtypes and other related disorders presents challenges for differential diagnosis. METHODS: We enrolled a total of 11 Chinese children with PHP in our study and analyzed their clinical characteristics, laboratory results, and genetic mutations. RESULTS: Among these 11 patients, nine of them (9/11) presented with resistance to parathyroid hormone (PTH); and nine (9/11) presented with an Albright's hereditary osteodystrophy (AHO) phenotype. GNAS abnormalities were detected in all 11 patients, including nine cases with GNAS gene variations and two cases with GNAS methylation defects. These GNAS variations included an intronic mutation (c.212 + 3_212 + 6delAAGT), three missense mutations (c.314C > T, c.308 T > C, c.1123G > T), two deletion mutations (c.565_568delGACT*2, c.74delA), and two splicing mutations (c.721 + 1G > A, c.432 + 1G > A). Three of these mutations, namely, c.314C > T, c.1123G > T, and c.721 + 1G > A, were found to be novel. This data was then used to assign a GNAS subtype to each of these patients with six cases diagnosed as PHP1a, two cases as PHP1b, one as PPHP, and two as POH. CONCLUSIONS: Evaluating patients with PTH resistance and AHO phenotype improved the genetic diagnosis of GNAS mutations significantly. In addition, our results suggest that when GNAS gene sequencing is negative, GNAS methylation study should be performed. Early genetic detection is required for the differential diagnosis of GNAS disorders and is critical to the clinician's ability to distinguish between heterotopic ossification in the POH and AHO phenotype.

Management of pseudohypoparathyroidism.

PURPOSE OF REVIEW: This review is timely given the 2018 publication of the first international Consensus Statement for the diagnosis and management of pseudohypoparathyroidism (PHP) and related disorders. The purpose of this review is to provide the knowledge needed to recognize and manage PHP1A, pseudopseudohypoparathyroidism (PPHP) and PHP1B - the most common of the subtypes - with an overview of the entire spectrum and to provide a concise summary of management for clinical use. This review will draw from recent literature as well as personal experience in evaluating hundreds of children and adults with PHP. RECENT FINDINGS: Progress is continually being made in understanding the mechanisms underlying the PHP spectrum. Every year, through clinical and laboratory studies, the phenotypes are elucidated in more detail, as are clinical issues such as short stature, brachydactyly, subcutaneous ossifications, cognitive/behavioural impairments, obesity and metabolic disturbances. Headed by a European PHP consortium, experts worldwide published the first international Consensus that provides detailed guidance in a systematic manner and will lead to exponential progress in understanding and managing these disorders. SUMMARY: As more knowledge is gained from clinical and laboratory investigations, the mechanisms underlying the abnormalities associated with PHP are being uncovered as are improvements in management.

A Case of Soft Tissue Ossifications: A Case Report.

CASE: A patient who had previously been diagnosed with fibrodysplasia ossificans progressiva was seen for hip pain and progressive soft tissue ossifications. Through a careful clinical examination, by which a subtype of brachydactyly was noted, the Albright hereditary osteodystrophy phenotype was recognized, and a new diagnosis of pseudopseudohypoparathyroidism was established. This paucisymptomatic condition often remains unidentified; however, its transmission can lead to more potentially serious diseases. CONCLUSIONS: A careful diagnostic process, including physical examination, is essential. Even if advanced tests exist, small clinical findings can lead to the proper conclusion. In our case, a finger pointed us in the right direction.

Screening of PRKAR1A and PDE4D in a Large Italian Series of Patients Clinically Diagnosed With Albright Hereditary Osteodystrophy and/or Pseudohypoparathyroidism.

The cyclic adenosine monophosphate (cAMP) intracellular signaling pathway mediates the physiological effects of several hormones and neurotransmitters, acting by the activation of G-protein coupled receptors (GPCRs) and several downstream intracellular effectors, including the heterotrimeric stimulatory G-protein (Gs), the cAMP-dependent protein kinase A (PKA), and cAMP-specific phosphodiesterases (PDEs). Defective G-protein-mediated signaling has been associated with an increasing number of disorders, including Albright hereditary osteodistrophy (AHO) and pseudohypoparathyroidism (PHP), a heterogeneous group of rare genetic metabolic disorders resulting from molecular defects at the GNAS locus. Moreover, mutations in PRKAR1A and PDE4D genes have been recently detected in patients with acrodysostosis (ACRDYS), showing a skeletal and endocrinological phenotype partially overlapping with AHO/PHP. Despite the high detection rate of molecular defects by currently available molecular approaches, about 30% of AHO/PHP patients still lack a molecular diagnosis, hence the need to screen patients negative for GNAS epi/genetic defects also for chromosomal regions and genes associated with diseases that undergo differential diagnosis with PHP. According to the growing knowledge on Gsα-cAMP signaling-linked disorders, we investigated our series of patients (n = 81) with a clinical diagnosis of PHP/AHO but negative for GNAS anomalies for the presence of novel genetic variants at PRKAR1A and PDE4D genes. Our work allowed the detection of 8 novel missense variants affecting genes so far associated with ACRDYS in 9 patients. Our data further confirm the molecular and clinical overlap among these disorders. We present the data collected from a large series of patients and a brief review of the literature in order to compare our findings with already published data; to look for PRKAR1A/PDE4D mutation spectrum, recurrent mutations, and mutation hot spots; and to identify specific clinical features associated with ACRDYS that deserve surveillance during follow-up. © 2016 American Society for Bone and Mineral Research.

Ablation of the Stimulatory G Protein α-Subunit in Renal Proximal Tubules Leads to Parathyroid Hormone-Resistance With Increased Renal Cyp24a1 mRNA Abundance and Reduced Serum 1,25-Dihydroxyvitamin D.

PTH regulates serum calcium, phosphate, and 1,25-dihydroxyvitamin D (1,25(OH)2D) levels by acting on bone and kidney. In renal proximal tubules (PTs), PTH inhibits reabsorption of phosphate and stimulates the synthesis of 1,25(OH)2D. The PTH receptor couples to multiple G proteins. We here ablated the α-subunit of the stimulatory G protein (Gsα) in mouse PTs by using Cre recombinase driven by the promoter of type-2 sodium-glucose cotransporter (Gsα(Sglt2KO) mice). Gsα(Sglt2KO) mice were normophosphatemic but displayed, relative to controls, hypocalcemia (1.19 ±0.01 vs 1.23 ±0.01 mmol/L; P < .05), reduced serum 1,25(OH)2D (59.3 ±7.0 vs 102.5 ±12.2 pmol/L; P < .05), and elevated serum PTH (834 ±133 vs 438 ±59 pg/mL; P < .05). PTH-induced elevation in urinary cAMP excretion was blunted in Gsα(Sglt2KO) mice (2- vs 4-fold over baseline in controls; P < .05). Relative to baseline in controls, PTH-induced reduction in serum phosphate tended to be blunted in Gsα(Sglt2KO) mice (-0.39 ±0.33 vs -1.34 ±0.36 mg/dL; P = .07). Gsα(Sglt2KO) mice showed elevated renal vitamin D 24-hydroxylase and bone fibroblast growth factor-23 (FGF23) mRNA abundance (∼3.4- and ∼11-fold over controls, respectively; P < .05) and tended to have elevated serum FGF23 (829 ±76 vs 632 ±60 pg/mL in controls; P = .07). Heterozygous mice having constitutive ablation of the maternal Gsα allele (E1(m-/+)) (model of pseudohypoparathyroidism type-Ia), in which Gsα levels in PT are reduced, also exhibited elevated serum FGF23 (474 ±20 vs 374 ±27 pg/mL in controls; P < .05). Our findings indicate that Gsα is required in PTs for suppressing renal vitamin D 24-hydroxylase mRNA levels and for maintaining normal serum 1,25(OH)2D.

[Paternal GNAS mutations: Which phenotypes? What genetic counseling?]. / Mutations paternelles de GNAS : quels phénotypes ? Quel conseil génétique ?

Parental imprinting and the type of the genetic alteration play a determinant role in the phenotype expression of GNAS locus associated to pseudohypoparathyroidism (PHP). GNAS locus gives rise to several different messenger RNA transcripts that are derived from the paternal allele, the maternal allele, or both and can be either coding or non-coding. As a consequence, GNAS mutations lead to a wide spectrum of phenotypes. An alteration in the coding sequence of the gene leads to a haplo-insufficiency and a dysmorphic phenotype (Albright's syndrome or AHO). AHO is a clinical syndrome defined by specific physical features including short stature, obesity, round-shaped face, subcutaneous ossifications, brachymetarcapy (mainly of the 4th and 5th ray). If the alteration is on the maternal allele, there is a hormonal resistance to the PTH at the kidney level and to the TSH at the thyroid level. The phenotype is known as pseudohypoparathyroidism type 1a (PHP1a). If the alteration is on the paternal allele, there are few clinical signs with no hormonal resistance and the phenotype is known as pseudopseudo hypoparathyroidism (pseudo-PPHP). Heterozygous GNAS mutations on the paternal GNAS allele were associated with intra uterin growth retardation (IUGR). Moreover, birth weights were lower with paternal GNAS mutations affecting exon 2-13 than with exon 1/intron 1 mutations suggesting a role for loss of function XLαs. Progressive osseous heteroplasia (POH) is a rare disease of ectopic bone formation, characterized by cutaneous and subcutaneous ossifications progressing towards deep connective and muscular tissues. POH is caused by a heterozygous GNAS inactivating mutation and has been associated with paternal inheritance. However, genotype/phenotype correlations suggest that there is no direct correlation between the ossifying process and parental origin, as there is high variability in heterotopic ossification. Clinical heterogeneity makes genetic counseling a very delicate matter, specifically where paternal inheritance is concerned as it can lead either to a mild expression of pseudo-PHP or to a severe one of POH.

Evidence of hormone resistance in a pseudo-pseudohypoparathyroidism patient with a novel paternal mutation in GNAS.

CONTEXT: Loss-of-function GNAS mutations lead to hormone resistance and Albright's hereditary osteodystrophy (AHO) when maternally inherited, i.e. pseudohypoparathyroidism-Ia (PHPIa), but cause AHO alone when located on the paternal allele, i.e. pseudoPHP (PPHP). OBJECTIVE: We aimed to establish the molecular diagnosis in a patient with AHO and evidence of hormone resistance. CASE: The patient is a female who presented at the age of 13.5years with short stature and multiple AHO features. No evidence for TSH or gonadotropin-resistance was present. Serum calcium and vitamin D levels were normal. However, serum PTH was elevated on multiple occasions (64-178pg/mL, normal: 9-52) and growth hormone response to clonidine or L-DOPA was blunted, suggesting hormone resistance and PHP-Ia. The patient had diminished erythrocyte Gsα activity and a novel heterozygous GNAS mutation (c.328 G>C; p.A109P). The mother lacked the mutation, and the father's DNA was not available. Hence, a diagnosis of PPHP also appeared possible, supported by low birth weight and a lack of AHO features associated predominantly with PHP-Ia, i.e. obesity and cognitive impairment. To determine the parental origin of the mutation, we amplified the paternally expressed A/B and biallelically expressed Gsα transcripts from the patient's peripheral blood RNA. While both wild-type and mutant nucleotides were detected in the Gsα amplicon, only the mutant nucleotide was present in the A/B amplicon, indicating that the mutation was paternal. CONCLUSION: These findings suggest that PTH and other hormone resistance may not be an exclusive feature of PHP-Ia and could also be observed in patients with PPHP.

Late-onset subcutaneous scalp calcifications in a patient with pseudo-pseudohypoparathyroidism.

Ectopic calcifications and even bone formation have been linked to GNAS gene mutations. A 51-year-old Caucasian female had been diagnosed of pseudo-pseudohypoparathyroidism (PPHP) in 1989. She has always had normal serum parathyroid hormone, calcium, and phosphorus levels. A non-contrast computed tomography of the head was done in 2013 and it showed finely speckled subcutaneous calcifications in the high convexity of the head. Cutaneous exploration did not show any abnormality. We herein report an unusual case of late-onset scalp calcifications in a patient with PPHP.

Pseudohypoparathyroidism vs. tricho-rhino-phalangeal syndrome: patient reclassification.

OBJECTIVES: Given that tricho-rhino-phalangeal syndrome (TRPS) and pseudohypoparathyroidism/pseudopseudohypoparathyroidism (PHP/PPHP) are very rare monogenic disorders that share some features (distinctive facies, short stature, brachydactyly and, in some patients, intellectual disability) that lead to their misdiagnosis in some cases, our objective was to identify clinical, biochemical or radiological signs that could help to distinguish these two syndromes. METHODS AND RESULTS: We report on two cases, which were referred to the Endocrinology and Pediatric Endocrinology Services for obesity. Clinical evaluation initially suggested the diagnosis of PHP-Ia [phenotype suggestive of Albright hereditary osteodystrophy (AHO) with parathyroid hormone (PTH) resistance] and PPHP (phenotype resembling AHO, without PTH resistance), but (epi)genetic analysis of the GNAS locus ruled out the suspected diagnosis. Further clinical re-evaluation prompted us to suspect TRPS, and this was confirmed genetically. CONCLUSION: TRPS was mistakenly identified as PHP/PPHP because of the coexistence of obesity and brachydactyly, with PTH resistance in one of the cases. Specific traits such as sparse scalp hair and a pear-shaped nose, present in both cases, can be considered pathognomonic signs of TRPS, which could help us to reach a correct diagnosis.

Mutations in pseudohypoparathyroidism 1a and pseudopseudohypoparathyroidism in ethnic Chinese.

An inactivating mutation in the GNAS gene causes either pseudohypoparathyroidism 1a (PHP1A) when it is maternally inherited or pseudopseudohypoparathyroidism (PPHP) when it is paternally inherited. We investigated clinical manifestations and mutations of the GNAS gene in ethnic Chinese patients with PHP1A or PPHP. Seven patients from 5 families including 4 girls and 2 boys with PHP1A and 1 girl with PPHP were studied. All PHP1A patients had mental retardation. They were treated with calcitriol and CaCO3 with regular monitoring of serum Ca levels, urinary Ca/Cr ratios, and renal sonography. Among them, 5 patients also had primary hypothyroidism suggesting TSH resistance. One female patient had a renal stone which was treated with extracorporeal shockwave lithotripsy. She had an increased urinary Ca/Cr ratio of 0.481 mg/mg when the stone was detected. We detected mutations using PCR and sequencing as well as analysed a splice acceptor site mutation using RT-PCR, sequencing, and minigene construct. We detected 5 mutations: c.85C>T (Q29*), c.103C>T (Q35*), c.840-2A>G (R280Sfs*21), c.1027_1028delGA (D343*), and c.1174G>A (E392K). Mutations c.840-2A>G and c.1027_1028delGA were novel. The c.840-2A>G mutation at the splice acceptor site of intron 10 caused retention of intron 10 in the minigene construct but skipping of exon 11 in the peripheral blood cells. The latter was the most probable mechanism which caused a frameshift, changing Arg to Ser at residue 280 and invoking a premature termination of translation at codon 300 (R280Sfs*21). Five GNAS mutations in ethnic Chinese with PHP1A and PPHP were reported. Two of them were novel. Mutation c.840-2A>G destroyed a spice acceptor site and caused exon skipping. Regular monitoring and adjustment in therapy are mandatory to achieve optimal therapeutic effects and avoid nephrolithiasis in patients with PHP1A.

Clinical characterization and molecular classification of 12 Korean patients with pseudohypoparathyroidism and pseudopseudohypoparathyroidism.

CONTEXT: Pseudohypoparathyroidism (PHP) is defined as resistance toward parathyroid hormones. PHP and pseudopseudohypoparathyroidism (PPHP) are rare disorders resulting from genetic and epigenetic aberrations within or upstream of the GNAS locus. This study investigated the clinical characteristics and performed a molecular analysis of PHP and PPHP. METHODS: A total of 12 patients with (P)PHP from 11 unrelated families (4 with PHP-Ia, 6 with PHP-Ib, and 2 with PPHP) were characterized using both clinical and molecular methods. Clinical features included the presenting symptoms, Albright hereditary osteodystrophy features, and resistance to hormones. Comprehensive analysis of the GNAS and STX16 loci was undertaken to investigate the molecular defects underlying (P)PHP. RESULTS: All PHP-Ib patients displayed hypocalcemic symptoms. All PHP-Ia patients showed resistance toward TSH, in addition to PTH. In most patients with PHP, when the diagnosis of PHP was first established, hypocalcemia and hyperphosphatemia were associated with a significant increase in serum PTH levels. One patient with PHP-Ia was diagnosed with growth hormone deficiency and showed a good response to human recombinant growth hormone therapy. 6 patients with PHP-Ia and PPHP showed 5 different mutations in the GNAS gene. 5 patients with PHP-Ib displayed a loss of differentially methylated region (DMR) imprints of the maternal GNAS. One PHP-Ib patient showed a de novo microdeletion in STX16 and a loss of methylation of exon A/B on the maternal allele. No patients revealed paternal disomy among 4 patients with PHP-Ib. CONCLUSIONS: Identification of the molecular causes of PHP and PPHP explains their distinctive clinical features and enables confirmation of the diagnosis and exact genetic counseling.

Paternal GNAS mutations lead to severe intrauterine growth retardation (IUGR) and provide evidence for a role of XLαs in fetal development.

CONTEXT: Heterozygous GNAS inactivating mutations cause pseudohypoparathyroidism type Ia (PHP-Ia) when maternally inherited and pseudopseudohypoparathyroidism (PPHP)/progressive osseous heteroplasia (POH) when paternally inherited. Recent studies have suggested that mutations on the paternal, but not the maternal, GNAS allele could be associated with intrauterine growth retardation (IUGR) and thus small size for gestational age. OBJECTIVES: The aim of the study was to confirm and expand these findings in a large number of patients presenting with either PHP-Ia or PPHP/POH. PATIENTS AND METHODS: We collected birth parameters (ie, gestational age, weight, length, and head circumference) of patients with either PHP-Ia (n = 29) or PPHP/POH (n = 26) with verified GNAS mutations. The parental allele carrying the mutation was assessed by investigating the parents or, when a de novo mutation was identified, through informative intragenic polymorphisms. RESULTS: Heterozygous GNAS mutations on either parental allele were associated with IUGR. However, when these mutations are located on the paternal GNAS allele, IUGR was considerably more pronounced than with mutations on the maternal allele. Moreover, birth weights were lower with paternal GNAS mutations affecting exons 2-13 than with exon 1/intron 1 mutations. CONCLUSIONS: These data indicate that a paternally derived GNAS transcript, possibly XLαs, is required for normal fetal growth and development and that this transcript affects placental functions. Thus, similar to other imprinted genes, GNAS controls growth and/or fetal development.

Sinus pauses and high-grade atrioventricular block in Albright's hereditary osteodystrophy with pseudopseudohypoparathyroidism.

Albright's hereditary osteodystrophy (AHO) is a rare inherited syndrome involving the molecular defects in the gene encoding the α subunit of the stimulatory G protein (Gsα). AHO has several variants, mainly pseudohypoparathyroidism (PHP) and pseudopseudohypoparathyroidism (PPHP). We present a family that share the same inactivating GNAS1 mutation, the daughter being affected by PPHP and her late father with PHP. The daughter, in her late teens, presented with a long history of presyncopal and syncopal attacks. Her father died suddenly in his mid-40 s. As expected, her laboratory tests to date have shown normal biochemistry and hormonal levels. Subsequently, an implantable loop recorder was inserted. This demonstrated extreme sinus pauses of >11 s and also high-grade atrioventricular block. A dual-chamber pacemaker was therefore inserted.

Brachydactyly mental retardation syndrome in differential diagnosis of pseudopseudohypoparathyroidism.

Patients with Albright hereditary osteodystrophy (AHO) phenotype are usually seen in pediatric endocrinology policlinics when they are evaluated for short stature and/or obesity. Brachydactyly mental retardation syndrome (BDMR, OMIM #600430) is a rare genetic disorder caused by aberrations of chromosomal region 2q37 and characterized with AHO-like phenotype without any hormone resistance. Diagnosis of BDMR is based on the detection of the deletion on the long arm of chromosome 2. Diagnosis can usually be made with karyotype analysis but sometimes chromosomal deletion can only be detected by fluorescent in situ hybridization (FISH) screening. We report a patient with the AHO phenotype whose karyotype was normal but who was diagnosed with BDMR with FISH analysis showing 2q deletion. In pediatric endocrinology practice, in patients with AHO phenotype but without parathormone (PTH) resistance, BDMR should be considered. For the diagnosis of BDMR, the subtelomeric region of chromosome 2 should be screened for deletion by FISH analysis even in patients with normal karyotypes.

Endocrine profile and phenotype-(epi)genotype correlation in Spanish patients with pseudohypoparathyroidism.

CONTEXT: Recent advances in genetics and epigenetics have revealed an overlap between molecular and clinical features of pseudohypoparathyroidism (PHP) subtypes, broadening the previous spectrum of PHP genotype-phenotype correlations and indicating limitations of the current classification of the disease. OBJECTIVES: The aim of the study was to screen patients with clinical diagnoses of PHP type I or pseudo-PHP for underlying molecular defects and explore possible correlations between molecular findings and clinical features. PATIENTS AND METHODS: We investigated the GNAS locus at the molecular level in 72 affected patients (46 women and 26 men) from 56 nonrelated families. Clinical data were obtained for 63 of these patients (38 women and 25 men). RESULTS: The molecular analysis showed that 35 patients carried structural mutations, 32 had loss of methylation, and 2 had a 2q37 deletion but did not reveal any (epi)mutation for 3 patients. Comparing these results and the clinical data, we observed that a younger age at diagnosis was associated with structural defects at the GNAS gene and epigenetic defects with a diagnosis later in life (9.19 ± 1.64 vs 24.57 ± 2.28 years, P < .0001). CONCLUSIONS: This first global review of PHP in Spain highlights the importance of a detailed clinical and genetic study of each patient and the integrated analysis of the findings from the two approaches. It may also help geneticists and clinicians to raise the suspicion of PHP earlier, reach more accurate diagnoses, and provide patients with PHP and their families with useful genetic information and counseling, thereby improving outcomes and quality of life.

Pseudohypoparathyroidism type Ia and pseudo-pseudohypoparathyroidism: the growing spectrum of GNAS inactivating mutations.

Pseudohypoparathyroidism (PHP) is a rare heterogeneous genetic disorder characterized by end-organ resistance to parathyroid hormone due to partial deficiency of the α subunit of the stimulatory G protein (Gsα), encoded by the GNAS gene. Heterozygous inactivating GNAS mutations lead to either PHP type Ia (PHP-Ia), when maternally inherited, or pseudo-pseudohypoparathroidism (PPHP), if paternally derived. Both diseases feature typical physical traits identified as Albright's hereditary osteodystrophy in the presence or absence of multihormone resistance, respectively. GNAS mutations are detected in 60-70% of affected subjects, most patients/families harbor private mutations and no genotype-phenotype correlation has been found to date. We investigated Gsα-coding GNAS exons in a large panel of PHP-Ia-PPHP patients collected over the past decade in the two Italian referring centers for PHP. Of 49 patients carrying GNAS mutations, we identified 15 novel mutations in 19 patients. No apparent correlation was found between clinical/biochemical data and results of molecular analysis. Furthermore, we summarized the current knowledge of GNAS molecular pathology and updated the GNAS-locus-specific database. These results further expand the spectrum of GNAS mutations associated with PHP/PPHP and underline the importance of identifying such genetic alterations to supplement clinical evaluation and genetic counseling.