Clinical and genetic characteristics of Pseudohypoparathyroidism in the Chinese population

(Epi)genetic and clinical characteristics in 84 patients with pseudohypoparathyroidism type 1B

OBJECTIVE

Pseudohypoparathyroidism type 1B (PHP1B) caused by methylation defects of differentially methylated regions (DMRs) on the GNAS locus can be categorized into groups according to etiologies and methylation defect patterns of the DMRs. The aim of this study was to clarify the clinical characteristics of each group.

DESIGN

Comprehensive molecular analyses consisting of methylation, copy number, and microsatellite analyses.

METHODS

Eighty-four patients with PHP1B were included in this study. We classified them into 5 groups, namely, autosomal dominant inheritance-PHP1B (Group 1, G1), sporadic-PHP1B (G2), and atypical-PHP1B (G3-G5), based on the methylation defect patterns in 4 DMRs on the GNAS locus and etiologies and evaluated the clinical findings in each group and compared them among the groups.

RESULTS

G2 had the youngest age and the highest serum intact parathyroid hormone levels among the 5 groups at the time of diagnosis. The most common symptoms at the time of diagnosis were tetany in G1, and seizures or loss of consciousness in G2. Albright's hereditary osteodystrophy and PHP-suggestive features were most frequently observed in the G2 proband. Nine patients had neurodevelopmental disorders (NDs) consisting of mild to borderline intellectual disability and/or developmental delay. There were no significant correlations between the average methylation ratios of 7 CpG sites in the GNAS-A/B:TSS-DMR and hormonal and biochemical findings.

CONCLUSION

This study revealed the differences in some clinical characteristics, particularly clinical features, and ages at the time of diagnosis between G2 and other groups and detailed NDs observed in some patients with PHP1B.

Explorative research on glucolipid metabolism and levels of adipokines in pseudohypoparathyroidism type 1 patients

BACKGROUND

Pseudohypoparathyroidism type 1 (PHP1) is a rare disease featuring hypocalcemia and elevated PTH level. Though disturbed calcium and phosphorus metabolism under PTH resistant have been widely studied, glucolipid metabolism abnormalities observed in PHP1 patients have received little attention. The aim of this research is to explore the glucolipid metabolism features in a rather large cohort of PHP1 patient. In the current study, PHP1 patients and primary hyperparathyroidism patients as well as normal control were recruited for the investigation. Glucolipid metabolic indices as well as the level of four adipokines were examined.

RESULTS

A total of 49 PHP1 patients, 64 PHPT patients and 30 healthy volunteers were enrolled. A trend of higher HOMA-β index was found in PHP1 patients than normal controls (median 97.08% vs 68.19%, p = 0.060). Both the PHP1 and PHPT group presented with significantly lower TNFα level compared to normal controls (average 10.74 pg/ml and 12.53 pg/ml vs 15.47 pg/ml, p = 0.002 and 0.041, respectively). FGF21 level was significantly higher in PHPT group than in PHP1 group (median 255.74 pg/ml vs 167.46 pg/ml, p = 0.019). No significant difference in glucolipid metabolic indices and adipokines was found between PHP1A or PHP1B patients and normal controls, while overweight/obese PHP1 patients tended to have higher leptin than normal-BMI cases (p = 0.055). Multiple linear regression analysis showed BMI rather than PTH or HOMA-IR to be an independent variable of leptin in PHP1.

CONCLUSION

Metabolic stress given upon especially overweight PHP1 patients may resulted in possible β-cell compensation. Elevated TNFα may be related with hyper-PTH level regardless of calcium level.

Genotype-phenotype correlations in pseudohypoparathyroidism type 1a patients: a systemic review

BACKGROUND

Pseudohypoparathyroidism type 1a (PHP1a) is a rare endocrine disease caused by partial defects of the α subunit of the stimulatory Guanosin triphosphate (GTP) binding protein (Gsα) resulting from maternal GNAS gene variation. The clinical manifestations are related to PTH resistance (hypocalcemia, hyperphosphatemia, and elevated serum intact PTH) in the presence or absence of multihormone resistance, and Albright's hereditary osteodystrophy (AHO).

OBJECTIVES

To summarize the molecular genetics results and clinical characteristics as well as to explore the correlations between them.

METHODS

Articles pertaining to PHP1a until May, 31, 2021 were reviewed and 527 patients with genetic diagnosis were included in the data analysis. The clinical characteristics and molecular genetics results of these patients were analyzed and compared to explore the correlations between them.

RESULTS

A total of 258 GNAS rare variants (RVs) were identified in 527 patients. The RVs were most commonly found in exons 1 and 7 (17.6% each), with frameshift (36.8%), and missense (31.3%) being the main types of RVs. The median age of onset was 5.0 years old. The most common clinical manifestations were elevation of PTH (86.7%) and AHO (87.5%). Thyroid stimulating hormone resistance was the most common hormone resistance (75.5%) other than PTH resistance. Patients with missense and in-frame RVs had lower incidence rates of the round face (P = .001) and subcutaneous ossifications (P < .001) than those with loss-of-function (non-sense, frameshift, splicing site variants, and large deletions) variants.

CONCLUSIONS

This study revealed the correlation between loss-of-function RVs with round faces and subcutaneous ossifications in PHP 1a patients. Further exploration of genotype-phenotype correlations through more standardized and prospective studies with long-term follow-up is necessary.

Full-length versus intact PTH concentrations in pseudohypoparathyroidism type 1 and primary hyperparathyroidism: clinical evaluation of immunoassays in individuals from China

PURPOSE

The application of the third-generation parathyroid hormone (PTH) assay [PTH(1-84) assay] for evaluating PTH levels in patients with pseudohypoparathyroidism type-1 (PHP1) is less popular than the second-generation assay. Therefore, we aimed at examining the conformity between the PTH(1-84) assay and the intact PTH (iPTH) assay, specifically examining their performance in individuals with PHP1 versus individuals with primary hyperparathyroidism (PHPT), compared to healthy controls.

METHODS

PTH(1-84) and iPTH assay were performed in patients with PHP1, patients with PHPT, and healthy volunteers. ∆PTH%, PTH(1-84)/iPTH (3^rd/2^nd ratio), iPTH/upper limit of normal (ULN), and PTH (1-84)/ULN of each group were calculated for comparison. Linear regression, Kappa conformity test, and Bland-Altman analysis of ∆PTH/mean of iPTH and PTH(1-84) (percent bias) plotted against the mean of iPTH and PTH(1-84) were performed to determine the conformance of PTH(1-84) assay with iPTH assay.

RESULTS

A total of 54 patients with PHP1, 127 patients with PHPT, and 65 healthy volunteers were enrolled in this study. All the three groups showed strong linear relationship between iPTH and PTH (1-84) (r² = 0.9661, 0.7733, and 0.9575, respectively). No significant differences were noted in 3^rd/2^nd ratio (median 0.76 vs. 0.72) between the PHP1 and PHPT groups (p > 0.05). Conformity examination showed the Kappa value was 0.778 and 0.395 for PHP1 and PHPT groups respectively. No difference in the Kappa values was found between PHP1A and PHP1B subgroups. Bland-Altman plot demonstrated that the proportion of data points that were plotted within mean ± 1.96 SD in PHP1, PHPT and normal control groups were 96.3%, 93.7%, and 98.5%, respectively. The mean percent bias of the three groups were 26.1%, 31.2%, and 17.0%, respectively. The range of mean ± 1.96 SD of percent bias of the three groups were 2.2%-50.0%, -14.3%-76.6%, and 6.7%-27.2%, respectively.

CONCLUSION

Although iPTH and PTH(1-84) values were both lower in the present PHP1 cohort than in the PHPT cohort, there appear to be differences in the relative agreement between both immunoassays, and in the relationship between the two values, especially in comparison to healthy controls. Whether these differences are due to differential accumulation of C-terminal fragments or other factors requires further study.

Different AHO phenotype in a Chinese family with a novel GNAS missense variant: a case report

Background

Albright’s hereditary osteodystrophy (AHO) is an inherited disorder which is caused by an inactivating variant in the GNAS gene. AHO appears associated to either pseudohypoparathyroidism 1a (PHP1a) when GNAS gene is maternally inherited or to pseudo-pseudohypoparathyroidism (PPHP) when it is paternally inherited. We describe the clinical and biochemical characteristics of two patients, a boy and his mother with a novel heterozygous missense variant of GNAS gene.

Case presentation

The boy presented with typical AHO phenotype (early-onset obesity, round face, short neck, shortened fifth metacarpal bone, developmental retardation, but without short stature and subcutaneous calcifications), multiple hormone resistance including PTH, TSH and ACTH, and mild calcification in the right basal ganglia. The mother only presented with brachydactyly and short stature, without hormone resistance and other signs of AHO. Whole-exome sequencing identified in the son and his mother a novel heterozygous missense variant (p. Val375Leu) in exon 13 of GNAS gene. The diagnosis of PHP-1a for the son and PPHP for the mother were confirmed.

Conclusion

This study further expands the spectrum of known GNAS pathogenic variants, and also demonstrates the heterogeneous phenotype of AHO due to a novel GNAS pathogenic variant.

Characterizing Cerebral Imaging and Electroclinical Features of Five Pseudohypoparathyroidism Cases Presenting with Epileptic Seizures

Objective

To characterize the cerebral imaging and electroclinical features and investigate their etiological contributions to seizures in pseudoparathyroidism (PHP).

Methods

The clinical symptoms, biochemical imaging by magnetic resonance imaging (MRI) and computed tomography (CT) tests, and electroencephalogram (EEG) manifestations of five PHP patients with seizures were retrospectively collected and analyzed.

Results

Physical examination showed an average stature in cases 2~4 and short stature in cases 1 and 5. X-ray tests suggested ectopic calcification in four patients. The seizures in four cases were effectively controlled with antiseizure medicines (ASMs). Cerebral CT scans showed extensive brain calcifications in the bilateral basal ganglia (all five cases), cerebellum (cases 1, 3, and 5), thalamus (case 4), and cerebral cortex. Cerebral MRI showed short T1 signals mainly in the basal ganglia. EEG records revealed focal EEG abnormalities, including abnormal slow waves and epileptiform discharges, mainly over the temporal and frontal lobes. The brain areas with focal EEG abnormalities and calcification did not always coincide.

Conclusion

The seizures in PHP can be focal to bilateral tonic–clonic. ASMs are effective in epilepsy combined with PHP. Intracranial calcification is not a reliable etiological cause of epilepsy in PHP patients.

Fahr syndrome discovered in adulthood revealing a rare GNAS mutation in pseudohypoparathyroidism type 1a in a Tunisian family

Pseudohypoparathyroidism (PHP) indicates a rare heterogeneous group of disorders characterized by hypocalcemia, hyperphosphatemia, increased serum concentration of parathyroid hormone (PTH), and insensitivity to the biologic activity of PTH. One of its most common types is PHP‐1a. In this report, we present a familial PHP‐1a and a novel mutation of the GNAS gene.

PHP1a is one of the rare and little‐known pathologies that can take a long time to be discovered. It associates a particular morphotype, subcutaneous calcifications and bone and renal resistance to parathormone. It is an inherited condition, which results from an abnormality in the GNAS gene. It is usually diagnosed in childhood. and few studies have addressed its natural history. Our report illustrates the natural history of a patient with PHP1A, which went undiagnosed until the age of 31 years. Through this clinical case, we emphasize the importance of a complete phosphocalcic balance in order to find and recognize the typical biochemical alterations associated with this pathology (hypocalcemia, hyperphosphatemia and high levels of PTH), the need for a detailed clinical examination because the phenotypic appearance often escapes notice and the identification of the responsible mutation in the index case is useful for screening other family members avoiding late diagnosis.

Pseudohypoparathyroidism during pregnancy and the postpartum period: A case series of five patients

OBJECTIVES

Pseudohypoparathyroidism (PHP) is a rare disease, especially when combined with pregnancy. We aimed to explore the changes in serum calcium/parathyroid hormone (PTH) level and medical treatment in a case series of PHP during pregnancy and the postpartum period.

METHODS

A total of five PHP patients with six pregnancies were enrolled. The classification of PHP was based on (epi)genetic analysis. Clinical characteristics, biochemical indices, and treatment strategies before, during, and after pregnancy were retrospectively collected.

RESULTS

All patients received calcium and vitamin D agents with nearly normal serum calcium before pregnancy except patient 2 who was found hypocalcemic during gestation. All patients chose Cesarean section, and one suffered preterm delivery due to oligoamnios. The neonatal birth weight ranged from 2,250 to 4,300 g, and all neonates were free of hypocalcemia-related symptoms. The change in calcium metabolism was inconsistent including stable, improved, or worsened during pregnancy. Serum PTH level remained low in the first two trimesters in patients with stable and improved conditions while increased in the last two trimesters in patients with a worsened condition. Serum calcium changed inconsistently while PTH increased consistently during lactation. For patients who did not breastfeed, calcium homeostasis improved after delivery.

CONCLUSION

Calcium homeostasis and medicine dosage changed differently in PHP patients during pregnancy and lactation. However, most patients had good pregnancy outcomes. Serum PTH levels might predict changes in calcium metabolism during pregnancy.

Bone turnover markers are associated with the PTH levels in different subtypes of pseudohypoparathyroidism type 1 patients

OBJECTIVE

Bone responsiveness to parathyroid hormone (PTH) in different subtypes of pseudohypoparathyroidism type 1 (PHP1) remains controversial. We aimed to investigate this phenomenon using bone turnover markers (BTMs) in a large cohort of PHP1 patients.

DESIGN

Retrospective study.

PATIENTS

Sixty-three PHP1 patients diagnosed by molecular analysis were used as subjects, and 48 sex- and age-matched patients with nonsurgical hypoparathyroidism (NS-HP) were used for comparison.

MEASUREMENTS

Bone turnover markers, alkaline phosphatase (ALP), C-terminal telopeptide of type I collagen (β-CTX) and related parameters in PHP1 were compared among different subtypes and with NS-HP.

RESULTS

Among all the PHP1 patients (15 PHP1A, 14 familial 1B and 34 sporadic 1B), 23.8% had elevated baseline BTM levels. No significant difference was found in the β-CTX levels among different subtypes. The β-CTX level was positively correlated with the PTH level for all PHP1, PHP1B and PHP1A patients (B = 0.001, 0.001 and 0.004, respectively; all p < .05). The BTM levels of PHP1 patients were significantly higher than those of NS-HP patients (β-CTX: 0.56 ng/ml vs. 0.20 ng/ml, p = .001; ALP: 105 U/L vs. 72 U/L, p = .001). The serum β-CTX levels in different PHP1 subtypes were all significantly higher than those in NS-HP patients in adults. Among the 22 followed up patients, changes in BTMs were associated with changes in PTH (β-CTX: r = .507, p = .023; ALP: r = .475, p = .034).

CONCLUSIONS

Bone tissues respond to PTH in different PHP1 subtypes, and it is reasonable to monitor and normalize PTH and BTMs in addition to the serum and urinary calcium levels in the follow-up of PHP1 patients.

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.

A novel GNAS mutation in pseudohypoparathyroidism type 1a in a Chinese man presented with recurrent seizure: a case report

BACKGROUND

Pseudohypoparathyroidism is a rare genetic disease characterized by hypocalcaemia and hyperphosphataemia due to the defect to the guanine nucleotide-binding protein alpha subunit (GNAS) gene. Patients with pseudoparathyroidism type 1a and 1c could manifest Albright's hereditary osteodystrophy and multiple hormone resistance including gonadotropin and thyroid stimulating hormone.

CASE PRESENTATION

Here we report a Chinese man who presented with fatigue, recurrent seizure and Albright's hereditary osteodystrophy. His genetic study revealed a heterozygote mutation in the GNAS gene [NM_000516.4(GNAS): c2787_2788del (p.Val930AspfsTer12)]. After calcium and calcitriol supplement, his seizures achieved partially remission.

CONCLUSIONS

We report a case of PHP1a or 1c with a novel frameshift mutation in GNAS gene in a patient presenting with AHO, as well as TSH and partial gonadotropin resistance. This mutation in this case has not been reported in literature and adds to the spectrum of genetic mutations related to PHP.

A novel long-range deletion spanning STX16 and NPEPL1 causing imprinting defects of the GNAS locus discovered in a patient with autosomal-dominant pseudohypoparathyroidism type 1B

BACKGROUND

Pseudohypoparathyroidism (PHP) is a rare disorder characterized by hypocalcemia, hyperphosphatemia, and resistance to parathyroid hormone (PTH). According to different GNAS mutations, PHP is divided into several subtypes, among which autosomal-dominant PHP1B (AD-PHP1B) is caused by STX16 deletion and epigenetic alteration of GNAS. Although the deletion of STX16 exons 2-6 is commonly observed, other mutations involving STX16 can also result in AD-PHP1B.

MATERIALS AND METHODS

The clinical information of a 38-year-old male PHP patient was collected. The genomic DNA from peripheral blood cells was extracted for genetic analysis of GNAS and upstream STX16 by methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and whole-exome sequencing (WES). Sanger sequencing was performed to verify the break point of the novel long-range deletion.

RESULTS

The patient's medical history of tetany and seizure as well as laboratory examination showing hypocalcemia and elevated PTH levels indicated the diagnosis of PHP. The results of MS-MLPA showed loss of methylation of GNAS A/B:TSS-DMR and half-reduced copy number of STX16 exon 1-9, which revealed the subtype of AD-PHP1B. Furthermore, the WES study displayed a 87.5 kb missing upstream of GNAS. A 87.5 kb deletion spanning STX16 and NPEPL1 together with an insertion of 28 bp of unknown origin was verified by PCR along with Sanger sequencing.

CONCLUSIONS

A novel deletion of 87.5 kb spanning STX16 and NPEPL1 was discovered in an AD-PHP1B patient, which provides new information on molecular defects leading to AD-PHP1B.

Cranio-Maxillofacial and Dental Findings in Albright's Hereditary Osteodystrophy and Pseudohypoparathyroidism

INTRODUCTION

The clinical phenotype of pseudohypoparathyroidism (PHP) is caused by Albright's Hereditary Osteodystrophy (AHO). Often, "round face" the only facial clinical sign reported in the literature. The aim of this study was to highlight various cranio-maxillofacial clinical findings associated with AHO.

RESULTS

Four patients presented with PHP type 1a. Only one patient exhibited the classical round face. All patients exhibited dental anomalies, class III malocclusion with maxillary retrusion, and a copper beaten appearance of the skull. One suffered from craniosynostosis.

CONCLUSION

The frequency of craniofacial and dental features associated with malocclusion should prompt careful follow-up, particularly during facial growth, in patients with AHO.