[Pseudohypoparathyroidism and variants: A translational medicine success story].

Pseudohypoparathyroidism (PHP) is an uncommon disorder which is characterized by end-organ PTH resistance. The genetic defect is located at the GNAS locus that encodes the alpha-subunit of the stimulatory G protein (Gα) and several splice variants thereof. This complex locus undergoes parental specific methylation changes that result in tissue-specific silencing of the paternal allele.

Overlapping Phenotypes Associated With , , and Mutations: A Cohort Study of Patients With Hypersensitivity to Vitamin D.

Mutations in (vitamin D 24-hydroxylase) and (renal phosphate transporter NPT2a) cause autosomal recessive Infantile Hypercalcemia type 1 and 2, illustrating links between vitamin D and phosphate metabolism. Patients may present with hypercalciuria and alternate between chronic phases with normal serum calcium but inappropriately high 1,25-(OH)D and appropriately low PTH, and acute phases with hypercalcemia with suppressed PTH. Mutations in and have been associated with phosphate wasting without hypercalcemia.

Differential diagnosis of vitamin D-related hypercalcemia using serum vitamin D metabolite profiling.

Genetic causes of vitamin D-related hypercalcemia are known to involve mutation of 25-hydroxyvitamin D-24-hydroxylase CYP24A1 or the sodium phosphate co-transporter SLC34A1, which result in excessive 1,25-(OH) D hormonal action. However, at least 20% of idiopathic hypercalcemia (IH) cases remain unresolved. In this case-control study, we used precision vitamin D metabolite profiling based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) of an expanded range of vitamin D metabolites to screen German and French cohorts of hypercalcemia patients, to identify patients with altered vitamin D metabolism where involvement of CYP24A1 or SLC34A1 mutation had been ruled out and who possessed normal 25-OH-D :24,25-(OH) D ratios.

Maternal Transmission Ratio Distortion of GNAS Loss-of-Function Mutations.

Pseudohypoparathyroidism type 1A (PHP1A) and pseudopseudohypoparathyroidism (PPHP) are two rare autosomal dominant disorders caused by loss-of-function mutations in the imprinted Guanine Nucleotide Binding Protein, Alpha Stimulating Activity (GNAS) gene, coding G α. PHP1A is caused by mutations in the maternal allele and results in Albright's hereditary osteodystrophy (AHO) and hormonal resistance, mainly to the parathormone (PTH), whereas PPHP, with AHO features and no hormonal resistance, is linked to mutations in the paternal allele. This study sought to investigate parental transmission of GNAS mutations.

High frequency of paternal iso or heterodisomy at chromosome 20 associated with sporadic pseudohypoparathyroidism 1B.

Pseudohypoparathyroidism 1B (PHP1B) is caused by maternal epigenetic defects in the imprinted GNAS cluster. PHP1B can follow an autosomal dominant mode of inheritance or occur sporadically (spor-PHP1B). These latter patients present broad methylation changes of two or more differentially methylated regions (DMR) that, when mimicking the paternal allele, raises the suspicious of the occurrence of paternal uniparental disomy of chromosome 20 (upd(20)pat).

Molecular characterization of a recurrent 10.9 kb CYP24A1 deletion in Idiopathic Infantile Hypercalcemia.

Loss-of-function mutations in CYP24A1 (MIM 126065 20q13.2), the gene encoding the 24-hydroxylase responsible for 25-OH-D and 1,25-(OH)D degradation, are identified in about 20% of patients presenting Idiopathic Infantile Hypercalcemia (IIH) (MIM 143880). Common features of this autosomal recessive condition included hypercalcemia with hypercalciuria, suppressed PTH and a high 25-OH-D:24,25-(OH)D ratio.

Diagnosis and management of pseudohypoparathyroidism and related disorders: first international Consensus Statement.

This Consensus Statement covers recommendations for the diagnosis and management of patients with pseudohypoparathyroidism (PHP) and related disorders, which comprise metabolic disorders characterized by physical findings that variably include short bones, short stature, a stocky build, early-onset obesity and ectopic ossifications, as well as endocrine defects that often include resistance to parathyroid hormone (PTH) and TSH. The presentation and severity of PHP and its related disorders vary between affected individuals with considerable clinical and molecular overlap between the different types. A specific diagnosis is often delayed owing to lack of recognition of the syndrome and associated features.

Genetic and Epigenetic Defects at the GNAS Locus Lead to Distinct Patterns of Skeletal Growth but Similar Early-Onset Obesity.

Pseudohypoparathyroidism type 1A (PHP1A), pseudoPHP (PPHP), and PHP type 1B (PHP1B) are caused by maternal and paternal GNAS mutations and abnormal methylation at maternal GNAS promoter(s), respectively. Adult PHP1A patients are reportedly obese and short, whereas most PPHP patients are born small. In addition to parathyroid hormone (PTH) resistance, PHP1A and PHP1B patients may display early-onset obesity.

Pseudohypoparathyroidism type 1B associated with assisted reproductive technology.

Evidence suggests an increased incidence of imprinting disorders in children conceived by assisted reproductive technologies (ART). Maternal loss-of-methylation at GNAS exon A/B, observed in pseudohypoparathyroidism type 1b (PHP1B), leads to decreased expression of the stimulatory Gsα. We present a patient conceived by ART, who presented at age 4 years with delayed neurocognitive development and persistently increased creatine kinase (CK).

Vitamin D-Dependent Rickets Type 1B (25-Hydroxylase Deficiency): A Rare Condition or a Misdiagnosed Condition?

Vitamin D requires a two-step activation by hydroxylation: The first step is catalyzed by hepatic 25-hydroxylase (CYP2R1, 11p15.2) and the second one is catalyzed by renal 1α-hydroxylase (CYP27B1, 12q13.1), which produces the active hormonal form of 1,25-(OH) D.

[Hypercalcemia and inactive mutation of CYP24A1. Case-study and literature review].

We present the case of a family whose members have high levels of serum calcium (hypercalcaemia) by loss of function of the enzyme vitamin D 24-hydroxylase due to bi-allelic mutations in the CYP24A1 gene: c.443 T>C (p.Leu148Pro) and c.

Improved Screening Test for Idiopathic Infantile Hypercalcemia Confirms Residual Levels of Serum 24,25-(OH) D in Affected Patients.

CYP24A1 mutations are now accepted as a cause of idiopathic infantile hypercalcemia (IIH). A rapid liquid-chromatography tandem mass spectrometry (LC-MS/MS)-based blood test enabling measurement of the 25-OH-D :24,25-(OH) D ratio (R) can identify IIH patients on the basis of reduced C24-hydroxylation of 25-OH-D by CYP24A1 in vivo. Although values of this ratio are significantly elevated in IIH, somewhat surprisingly, serum 24,25-(OH) D remains detectable.

Calcium pyrophosphate deposition disease revealing a hypersensitivity to vitamin D.

Objective: Hypersensitivity to vitamin D (HVD) due to a loss of function mutation of the CYP24A1 gene, which encodes vitamin D catabolizing enzyme was initially described as a cause of acute hypercalcemia in children and chronic renal diseases in adults.

Methods: We describe the first case of a patient presenting a calcium pyrophosphate deposition disease (CPDD) revealing a HVD.

Results: An abnormality of phospho-calcic metabolism was discovered during the course of an etiological workup for CPDD in a 52-year-old patient.

A Large Inversion Involving GNAS Exon A/B and All Exons Encoding Gsα Is Associated With Autosomal Dominant Pseudohypoparathyroidism Type Ib (PHP1B).

Pseudohypoparathyroidism type Ib (PHP1B) is characterized primarily by resistance to parathyroid hormone (PTH) and thus hypocalcemia and hyperphosphatemia, in most cases without evidence for Albright hereditary osteodystrophy (AHO). PHP1B is associated with epigenetic changes at one or several differentially-methylated regions (DMRs) within GNAS, which encodes the α-subunit of the stimulatory G protein (Gsα) and splice variants thereof. Heterozygous, maternally inherited STX16 or GNAS deletions leading to isolated loss-of-methylation (LOM) at exon A/B alone or at all maternal DMRs are the cause of autosomal dominant PHP1B (AD-PHP1B).

Genotype-Phenotype Relationship in Patients and Relatives with SHOX Region Anomalies in the French Population.

Background: The aim of our study was to describe a large population with anomalies involving the SHOX region, responsible for idiopathic short stature and Léri-Weill dyschondrosteosis (LWD), and to identify a possible genotype/phenotype correlation.

Methods: We performed a retrospective multicenter study on French subjects with a SHOX region anomaly diagnosed by multiplex ligation-dependent probe amplification or Sanger sequencing. Phenotypes were collected in each of the 7 genetic laboratories practicing this technique for SHOX analysis.

Hyperparathyroidism complicating CYP 24A1 mutations.

CYP24A1 gene mutations induce infantile hypercalcemia, with high 1,25(OH)D contrasting with low PTH levels. The adult phenotype is not well known. Two unrelated adult patients were referred for nephrolithiasis, hypertension, hypercalcemia, hypercalciuria, normal 25-OHD levels, and inappropriate PTH levels (22 to 92pg/mL;N: 15-68) suggesting primary hyperparathyroidism, leading to surgery.

Expanding the Spectrum of Founder Mutations Causing Isolated Gonadotropin-Releasing Hormone Deficiency.

Context: Loss of function (LoF) mutations in more than 20 genes are now known to cause isolated GnRH deficiency (IGD) in humans. Most causal IGD mutations are typically private, ie, limited to a single individual/pedigree. However, somewhat paradoxically, four IGD genes (GNRH1, TAC3, PROKR2, and GNRHR) have been shown to harbor LoF founder mutations that are shared by multiple unrelated individuals.

[Paternal GNAS mutations: Which phenotypes? What genetic counseling?].

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.

Loss of methylation at GNAS exon A/B is associated with increased intrauterine growth.

Context: GNAS is one of few genetic loci that undergo allelic-specific methylation resulting in the parent-specific expression of at least four different transcripts. Due to monoallelic expression, heterozygous GNAS mutations affecting either paternally or maternally derived transcripts cause different forms of pseudohypoparathyroidism (PHP), including autosomal-dominant PHP type Ib (AD-PHP1B) associated with loss of methylation (LOM) at exon A/B alone or sporadic PHP1B (sporPHP1B) associated with broad GNAS methylation changes. Similar to effects other imprinted genes have on early development, we recently observed severe intrauterine growth retardation in newborns, later diagnosed with pseudopseudohypoparathyroidism (PPHP) because of paternal GNAS loss-of-function mutations.

Diagnosis and management of congenital hypothyroidism associated with pseudohypoparathyroidism.

Unlabelled: Hypothyroidism is a particular condition observed in pseudohypoparathyroidism (PHP), a rare disorder characterized by parathyroid (PTH) resistance leading to hypocalcemia and hyperphosphatemia associated with a GNAS (guanine nucleotide-binding protein α-subunit) mutation (PHP1A) or epimutation (PHP1B). To determine the presence of hypothyroidism at birth we conducted a retrospective study in our cohort of patients presenting with either PHP1A (n = 116) or PHP1B (n = 99). We also investigated patients presenting at birth with congenital hypothyroidism (CH) and a eutopic thyroid gland for phosphocalcium abnormalities suggesting PTH resistance and PHP.

Kidney function and influence of sunlight exposure in patients with impaired 24-hydroxylation of vitamin D due to CYP24A1 mutations.

Loss-of-function mutations of CYP24A1, the enzyme that converts the major circulating and active forms of vitamin D to inactive metabolites, recently have been implicated in idiopathic infantile hypercalcemia. Patients with biallelic mutations in CYP24A1 present with severe hypercalcemia and nephrocalcinosis in infancy or hypercalciuria, kidney stones, and nephrocalcinosis in adulthood. We describe a cohort of 7 patients (2 adults, 5 children) presenting with severe hypercalcemia who had homozygous or compound heterozygous mutations in CYP24A1.

TSH elevations as the first laboratory evidence for pseudohypoparathyroidism type Ib (PHP-Ib).

Hypocalcemia and hyperphosphatemia because of resistance toward parathyroid hormone (PTH) in the proximal renal tubules are the most prominent abnormalities in patients affected by pseudohypoparathyroidism type Ib (PHP-Ib). In this rare disorder, which is caused by GNAS methylation changes, resistance can occur toward other hormones, such as thyroid-stimulating hormone (TSH), that mediate their actions through G protein-coupled receptors. However, these additional laboratory abnormalities are usually not recognized until PTH-resistant hypocalcemia becomes clinically apparent.