Practice patterns for chronic hypoparathyroidism: data from patients and physicians in France.

Context: Recent guidelines have provided recommendations for the care of patients with chronic hypoparathyroidism. Very little is known about actual physicians' practices or their adherence to such guidelines. Objective: To describe the physicians' practice patterns and their compliance with international guidelines. Design: The cohort studies included were Épi-Hypo (118 physicians and 107 patients, from September 2016 to December 2019) and ePatients (110 patients, November 2019). Methods: Internet-based cohorts involving all settings at a nationwide level (France). Participants were (i) physicians treating patients with chronic hypoparathyroidism and patients with chronic hypoparathyroidism either participating in the (ii) Épi-Hypo study (Épi-Hypo 2019 patients), or (iii) Hypoparathyroidism France, the national representative association (ePatients). Results: The physicians' specialties were mainly endocrinology (61%), nephrology (28%), family medicine (2.5%), pediatrics (2.5%), rheumatology (2%), or miscellaneous (4%) and 45% were practicing in public universities. The median number of pharmaceutical drug classes prescribed was three per patient. The combination of active vitamin D and calcium salt was given to 59 and 58% of ePatients and Épi-Hypo 2019 patients, respectively. Eighty-five percent of ePatients and 87% of physicians reported monitoring plasma calcium concentrations at a steady state at least twice a year. In 32 and 26% of cases, respectively, ePatients and physicians reported being fully in accordance with international guidelines that recommend targeting symptoms, plasma calcium and phosphate values, and urine calcium excretion. Conclusions: The care of patients with chronic hypoparathyroidism involves physicians with very different practices, so guidelines should include and target other specialists as well as endocrinologists. Full adherence to the guidelines is low in France.

[A complex case of renal phosphate wasting ]. / Une fuite rénale de phosphates complexe .

We describe here the case report of a young man of 34-years old suffering from a haemorrhagic rectocolitis and presenting with marked hypophosphatemia secondary to an infusion of ferric-carboxymaltose. The renal phosphate wasting was asserted by a very low renal maximal reabsorption rate of phosphate associated with a high plasma FGF-23 level. Three months later we explored the patient and his father since we learnt that both of them had suffered from kidney stones for years with marked hypercalciuria. Kidney stones were composed of weddellite and carbapatite. We suspected a familial phosphate renal wasting syndrome but however no mutation of the renal phosphate carriers could be identified.

Recommendations for Diagnosis and Treatment of Pseudohypoparathyroidism and Related Disorders: An Updated Practical Tool for Physicians and Patients.

Patients affected by pseudohypoparathyroidism (PHP) or related disorders are characterized by physical findings that may include brachydactyly, a short stature, a stocky build, early-onset obesity, ectopic ossifications, and neurodevelopmental deficits, as well as hormonal resistance most prominently to parathyroid hormone (PTH). In addition to these alterations, patients may develop other hormonal resistances, leading to overt or subclinical hypothyroidism, hypogonadism and growth hormone (GH) deficiency, impaired growth without measurable evidence for hormonal abnormalities, type 2 diabetes, and skeletal issues with potentially severe limitation of mobility. PHP and related disorders are primarily clinical diagnoses. Given the variability of the clinical, radiological, and biochemical presentation, establishment of the molecular diagnosis is of critical importance for patients. It facilitates management, including prevention of complications, screening and treatment of endocrine deficits, supportive measures, and appropriate genetic counselling. Based on the first international consensus statement for these disorders, this article provides an updated and ready-to-use tool to help physicians and patients outlining relevant interventions and their timing. A life-long coordinated and multidisciplinary approach is recommended, starting as far as possible in early infancy and continuing throughout adulthood with an appropriate and timely transition from pediatric to adult care.

"Isolated" Amelogenesis Imperfecta Associated with DLX3 Mutation: A Clinical Case.

Amelogenesis imperfecta (AI) represents rare tooth anomalies that affect the quality and/or quantity of the enamel. Clinical phenotypes display a wide spectrum, ranging from mild color changes to severe structural alterations with daily pain. However, all affect the quality of life because of mechanical, psychological, esthetic, and/or social repercussions. Several gene mutations have been linked to AI as a nonsyndromic (isolated) phenotype or a wider syndrome. This case report aimed to present a family with dental structure anomalies followed up in the dental department of the Louis Mourier Hospital (APHP, France) for their extremely poor dental condition. The proband and his mother were clinically diagnosed with AI, and genetic analysis revealed an already described variant in DLX3. Then, the family was further examined for tricho-dento-osseous syndrome. This report illustrates the challenge of diagnosing dental structure anomalies, specifically AI, in adults and highlights the need for an accurate and accessible molecular diagnosis for those anomalies to discriminate between isolated and syndromic pathologies.

Clinical characteristics of familial hypocalciuric hypercalcaemia type 1: A multicentre study of 77 adult patients.

OBJECTIVE: Familial hypocalciuric hypercalcaemia type 1 (FHH1), related to heterozygous loss-of-function mutations of the calcium-sensing receptor gene, is the main differential diagnosis for primary hyperparathyroidism. The aim of our study was to describe clinical characteristics of adult patients living in France with a genetically confirmed FHH1. DESIGN AND PATIENTS: This observational, retrospective, multicentre study included 77 adults, followed up in 32 clinical departments in France, with a genetic FHH1 diagnosis between 2001 and 2012. RESULTS: Hypercalcaemia was diagnosed at a median age of 53 years [IQR: 38-61]. The diagnosis was made after clinical manifestations, routine analysis or familial screening in 56, 34 and 10% of cases, respectively, (n = 58; data not available for 19 patients). Chondrocalcinosis was present in 11/51 patients (22%), bone fractures in 8/56 (14%) and renal colic in 6/55 (11%). The median serum calcium was 2.74 mmol/L [IQR: 2.63-2.86 mmol/L], the median plasma parathyroid hormone level was 4.9 pmol/L [3.1-7.1], and the median 24-hour urinary calcium excretion was 2.8 mmol/24 hours [IQR: 1.9-4.0]. Osteoporosis (dual X-ray absorptiometry) or kidney stones (renal ultrasonography) were found in 6/38 patients (16%) and 9/32 patients (28%), respectively. Fourteen patients (18%) underwent parathyroid surgery; parathyroid adenoma was found in three patients (21%) and parathyroid hyperplasia in nine patients (64%). No correlation between genotype and phenotype was established. CONCLUSION: This large cohort study demonstrates that FHH1 clinical characteristics can be atypical in 33 patients (43%). Clinicians should be aware of this rare differential diagnosis in order to adopt an appropriate treatment strategy.

Hyperparathyroidism in Patients With X-Linked Hypophosphatemia.

X-linked hypophosphatemia (XLH) is characterized by increased activity of circulating FGF23 resulting in renal phosphate wasting and abnormal bone mineralization. Hyperparathyroidism may develop in XLH patients; however, its prevalence, pathogenesis, and clinical presentation are not documented. This observational study (CNIL 171036 v 0) recruited XLH adult patients in a single tertiary referral center. Each patient was explored in standardized conditions and compared with two healthy volunteers, matched for sex, age, and 25-OH vitamin D concentrations. The primary endpoint was the proportion of patients with hyperparathyroidism. The secondary endpoints were the factors influencing serum parathyroid hormone (PTH) concentrations and the prevalence of hypercalcemic hyperparathyroidism. Sixty-eight patients (51 women, 17 men) were enrolled and matched with 136 healthy volunteers. Patients had higher PTH concentrations compared with healthy controls (53.5 ng/L, interquartile range [IQR] 36.7-72.7 versus 36.0 ng/L, IQR 27.7-44.0, p < .0001). Hyperparathyroidism was observed in 17 patients of 68 (25%). In patients, a positive relationship between PTH and calcium concentrations and a negative relationship between PTH and phosphate concentrations were observed. Seven (10%) patients (3 premenopausal women, 1 postmenopausal woman, and 3 men) were diagnosed with hypercalcemic hyperparathyroidism. All underwent parathyroid surgery, with consecutive normalization of calcium and PTH concentrations. Hyperparathyroidism is a frequent complication in XLH adult patients. Disruption of the physiological regulation of PTH secretion contributes to parathyroid disease. Early-onset hypercalcemic hyperparathyroidism can be effectively and safely cured by surgical resection. © 2020 American Society for Bone and Mineral Research.

Shortened Fingers and Toes: GNAS Abnormalities are Not the Only Cause.

The PTH/PTHrP receptor (PTHR1) mediates the actions of parathyroid hormone (PTH) and PTH-related peptide (PTHrP) by coupling this G protein-coupled receptor (GPCR) to the alpha-subunit of the heterotrimeric stimulatory G protein (Gsα) and thereby to the formation of cAMP. In growth plates, PTHrP-dependent activation of the cAMP/PKA second messenger pathway prevents the premature differentiation of chondrocytes into hypertrophic cells resulting in delayed growth plate closure. Heterozygous mutations in GNAS, the gene encoding Gsα, lead to a reduction in cAMP levels in growth plate chondrocytes that is sufficient to cause shortening of metacarpals and/or -tarsals, i. e. typical skeletal aspects of Albright's Hereditary Osteodystrophy (AHO). However, heterozygous mutations in other genes, including those encoding PTHrP, PRKAR1A, PDE4D, and PDE3A, can lead to similar or even more pronounced acceleration of skeletal maturation that is particularly obvious in hands and feet, and reduces final adult height. Genetic mutations other than those resulting in Gsα haploinsufficiency thus reduce intracellular cAMP levels in growth plate chondrocytes to a similar extent and thereby accelerate skeletal maturation.

McCune Albright syndrome is a genetic predisposition to intraductal papillary and mucinous neoplasms of the pancreas associated pancreatic cancer in relation with GNAS somatic mutation - a case report.

RATIONALE: Intraductal papillary and mucinous neoplasms of the pancreas (IPMN) are preneoplastic lesions diagnosed with an increasing incidence. Recently, several groups have described, in up to 70% of IPMN, activating mutations of the G-protein alpha stimulatory sub-unit (Gsα subunit) gene (GNAS). GNAS-activating somatic, post-zygotic, mutations are also associated with McCune-Albright syndrome (MCAS) characterized by fibrous dysplasia, precocious puberty, and café-au-lait spots. PATIENT CONCERNS: We herein report a patient with McCune Albright Syndrome that presented with malignant IPMN and underwent pancreatic resection. DIAGNOSES AND INTERVENTIONS: Leucocyte and duodenum juice DNA analysis, endoscopically collected from secretin-stimulated pancreatic juice revealed the same (GNAS) activating mutation also found in the invasive pancreatic colloid adenocarcinoma arising from intestinal subtype IPMN. OUTCOMES: Thirty months after surgery, the patient was alive with recurrence (bone only metastasis). LESSONS: In this observation, we show that MCAS should be view as a new genetic predisposition to IPMN associated pancreatic cancer, and consequently a targeted screening in this high-risk population might be proposed.

GNAS but Not Extended RAS Mutations Spectrum are Associated with a Better Prognosis in Intraductal Pancreatic Mucinous Neoplasms.

BACKGROUND: The management of intraductal papillary mucinous neoplasms (IPMNs) is mainly based on imaging features and clinical symptoms, and remains challenging. OBJECTIVE: The aim of this study was to assess GNAS, RAS family (KRAS, NRAS and HRAS), BRAF, and PIK3CA mutation status in resected IPMNs and correlate it with clinicopathological characteristics and patient survival. METHODS: Overall, 149 consecutive unselected patients who underwent pancreatectomy for IPMNs were included. After dissection from formalin-fixed and paraffin-embedded tumors, GNAS mutational screening was assessed by allelic discrimination using Taqman® probes and confirmed by SNaPshot analysis. RAS family, BRAF, and PIK3CA mutational screening was assessed by high resolution melt and Sanger sequencing. RESULTS: Gastric- and intestinal-type IPMNs were the most frequent lesions (52% and 41%, respectively). Intestinal-type IPMNs were more frequently associated high-grade dysplasia (49%) and were the only IPMNs associated with colloid-type carcinoma. All pancreatobiliary IPMNs were invasive lesions, located in the main pancreatic duct. GNAS-activating mutations were strongly associated with the intestinal phenotype (p < 10-4), while RAS pathway mutations were not associated with any particular phenotype. Mutations within other members of the epidermal growth factor receptor (EGFR) pathway were very rare (2%). GNAS-mutated IPMNs were rarely invasive (11%) and almost exclusively (83%) of the colloid type. For invasive lesions, multivariate analyses determined that only node negativity was associated with improved cancer-specific survival, but, in univariate analysis, GNAS mutation was associated with prolonged survival. CONCLUSION: In patients selected for surgery, GNAS mutation analysis and tumor phenotype can help to better predict patient prognosis. In the near future, a more precise mutational analysis of IPMNs might help to better tailor their management.

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. The participants in this Consensus Statement agreed that the diagnosis of PHP should be based on major criteria, including resistance to PTH, ectopic ossifications, brachydactyly and early-onset obesity. The clinical and laboratory diagnosis should be confirmed by a molecular genetic analysis. Patients should be screened at diagnosis and during follow-up for specific features, such as PTH resistance, TSH resistance, growth hormone deficiency, hypogonadism, skeletal deformities, oral health, weight gain, glucose intolerance or type 2 diabetes mellitus, and hypertension, as well as subcutaneous and/or deeper ectopic ossifications and neurocognitive impairment. Overall, a coordinated and multidisciplinary approach from infancy through adulthood, including a transition programme, should help us to improve the care of patients affected by these disorders.

Progression of Mineral Ion Abnormalities in Patients With Jansen Metaphyseal Chondrodysplasia.

Context: Five different activating PTH/PTH-related peptide (PTHrP) receptor (PTHR1) mutations have been reported as causes of Jansen metaphyseal chondrodysplasia (JMC), a rare disorder characterized by severe growth plate abnormalities and PTH-independent hypercalcemia. Objectives: Assess the natural history of clinical and laboratory findings in 24 patients with JMC and characterize the disease-causing mutant receptors in vitro. Patients and Methods: The H223R mutation occurred in 18 patients. T410P, I458R and I458K each occurred in single cases; T410R was present in a father and his two sons. Laboratory records were analyzed individually and in aggregate. Results: Postnatal calcium levels were normal in most patients, but elevated between 0.15 and 10 years (11.8 ± 1.37 mg/dL) and tended to normalize in adults (10.0 ± 1.03 mg/dL). Mean phosphate levels were at the lower end of the age-specific normal ranges. Urinary calcium/creatinine (mg/mg) were consistently elevated (children, 0.80 ± 0.40; adults, 0.28 ± 0.19). Adult heights were well below the 3rd percentile for all patients, except for those with the T410R mutation. Most patients with JMC had undergone orthopedic surgical procedures, most had nephrocalcinosis, and two had advanced chronic kidney disease. The five PTHR1 mutants showed varying degrees of constitutive and PTH-stimulated cAMP signaling activity when expressed in HEK293 reporter cells. The inverse agonist [L11,dW12,W23,Y36]PTHrP(7-36) reduced basal cAMP signaling for each PTHR1 mutant. Conclusions: Except for T410R, the other PTHR1 mutations were associated with indistinguishable mineral ion abnormalities and cause similarly severe growth impairment. Hypercalciuria persisted into adulthood. An inverse agonist ligand effectively reduced in vitro PTH-independent cAMP formation at all five PTHR1 mutants, suggesting a potential path toward therapy.

Pro-FHH: A Risk Equation to Facilitate the Diagnosis of Parathyroid-Related Hypercalcemia.

Context: Parathyroid-related hypercalcemia is due to primary hyperparathyroidism (PHPT) or to familial hypocalciuric hypercalcemia (FHH). PHPT can lead to complications that necessitate parathyroidectomy. FHH is a rare genetic disease resembling PHPT; surgery is ineffective. A reliable method for distinguishing FHH from PHPT is needed. Objective: To develop an easy-to-use tool to predict if a patient has PHPT. Design: Retrospective analysis of two prospective cohorts. Development of an unsupervised risk equation (Pro-FHH). Setting: University hospitals in Paris, France, and Aarhus, Denmark. Participants: Patients (Paris: 65 with FHH, 85 with PHPT; Aarhus: 38 with FHH, 55 with PHPT) were adults with hypercalcemia and PTH concentration within normal range. Main Outcome Measures: Performance of Pro-FHH to predict PHPT. Results: Pro-FHH takes into account plasma calcium, PTH, and serum osteocalcin concentrations, and calcium-to-creatinine clearance ratio calculated from 24-hour urine collection (24h-CCCR). In the Paris cohort, area under the receiver operating characteristic curve (AUROC) of Pro-FHH was 0.961, higher than that of 24h-CCCR. With a cutoff value of 0.928, Pro-FHH had 100% specificity and 100% positive predictive value for the diagnosis of PHPT; it correctly categorized 51 of 85 patients with PHPT; the remaining 34 were recommended to undergo genetic testing. No patients with FHH were wrongly categorized. In an independent cohort from Aarhus, AUROC of Pro-FHH was 0.951, higher than that of 24h-CCCR. Conclusion: Pro-FHH effectively predicted whether a patient has PHPT. A prospective trial is necessary to assess its usefulness in a larger population and in patients with elevated PTH concentration.

Hyperphosphatemic tumoral calcinosis caused by FGF23 compound heterozygous mutations: what are the therapeutic options for a better control of phosphatemia?

BACKGROUND: Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disease caused by mutations in genes encoding FGF23 or its regulators, and leading to functional deficiency or resistance to fibroblast growth factor 23 (FGF23). Subsequent biochemical features include hyperphosphatemia due to increased renal phosphate reabsorption, and increased or inappropriately normal 1,25-dihydroxyvitamin D (1,25-D) levels. CASE-DIAGNOSIS/TREATMENT: A 15-year-old girl was referred for a 1.2-kg-calcified mass of the thigh, with hyperphosphatemia (2.8 mmol/L); vascular impairment and soft tissue calcifications were already present. DNA sequencing identified compound heterozygous mutations in the FGF23 gene. Management with phosphate dietary restriction, phosphate binders (sevelamer, aluminum, nicotinamide), and acetazolamide moderately decreased serum phosphate levels; oral ketoconazole was secondary administered, leading to significantly decreased 1,25-D levels albeit only moderate additionally decreased phosphate levels. However, therapeutic compliance was questionable. Serum phosphate levels always remained far above the upper normal limit for age. The patient presented with two relapses of the thigh mass, requiring further surgery. CONCLUSIONS: We suggest that control of phosphate metabolism is crucial to prevent recurrences and vascular complications in HFTC; however, the medical management remains challenging.

Mutations causing acrodysostosis-2 facilitate activation of phosphodiesterase 4D3.

Type 2 acrodysostosis (ACRDYS2), a rare developmental skeletal dysplasia characterized by short stature, severe brachydactyly and facial dysostosis, is caused by mutations in the phosphodiesterase (PDE) 4D (PDE4D) gene. Several arguments suggest that the mutations should result in inappropriately increased PDE4D activity, however, no direct evidence supporting this hypothesis has been presented, and the functional consequences of the mutations remain unclear. We evaluated the impact of four different PDE4D mutations causing ACRDYS2 located in different functional domains on the activity of PDE4D3 expressed in Chinese hamster ovary cells. Three independent approaches were used: the direct measurement of PDE activity in cell lysates, the evaluation of intracellular cAMP levels using an EPAC-based (exchange factor directly activated by cAMP) bioluminescence resonance energy transfer sensor , and the assessment of PDE4D3 activation based on electrophoretic mobility. Our findings indicate that PDE4D3s carrying the ACRDYS2 mutations are more easily activated by protein kinase A-induced phosphorylation than WT PDE4D3. This occurs over a wide range of intracellular cAMP concentrations, including basal conditions, and result in increased hydrolytic activity. Our results provide new information concerning the mechanism whereby the mutations identified in the ACRDYS2 dysregulate PDE4D activity, and give insights into rare diseases involving the cAMP signaling pathway. These findings may offer new perspectives into the selection of specific PDE inhibitors and possible therapeutic intervention for these patients.

Phenotypic Variability in a Family with Acrodysostosis Type 2 Caused by a Novel PDE4D Mutation Affecting the Serine Target of Protein Kinase-A Phosphorylation.

Acrodysostosis is a very rare congenital multisystem condition characterized by skeletal dysplasia with severe brachydactyly, midfacial hypoplasia, and short stature, varying degrees of intellectual disability, and possible resistance to multiple G protein-coupled receptor signalling hormones. Two distinct subtypes are differentiated: acrodysostosis type 1 resulting from defects in protein kinase type 1-α regulatory subunit and acrodysostosis type 2 caused by mutations in phosphodiesterase 4D (PDE4D). Most cases are sporadic. We report on a rare multigenerational familial case of acrodysostosis type 2 due to a novel autosomal dominantly inherited PDE4D mutation. A 3.5-year-old boy presented with short stature, midfacial hypoplasia, severe brachydactyly, developmental delay, and behavioural problems. Laboratory investigations revealed mild thyrotropin resistance. His mother shared some characteristic features, such as midfacial hypoplasia and severe brachydactyly, but did not show short stature, intellectual disability or hormonal resistance. Genetic analysis identified the identical, novel heterozygous missense mutation of the PDE4D gene c.569C>T (p.Ser190Phe) in both patients. This case illustrates the significant phenotypic variability of acrodysostosis even within one family with identical mutations. Hence, a specific clinical diagnosis of acrodysostosis remains challenging because of great interindividual variability and a substantial overlap of the two subtypes as well as with other related Gsα-cAMP-signalling-linked disorders.

Knock-In of the Recurrent R368X Mutation of PRKAR1A that Represses cAMP-Dependent Protein Kinase A Activation: A Model of Type 1 Acrodysostosis.

In humans, activating mutations in the PRKAR1A gene cause acrodysostosis 1 (ACRDYS1). These mutations result in a reduction in PKA activation caused by an impaired ability of cAMP to dissociate mutant PRKAR1A from catalytic PKA subunits. Two striking features of this rare developmental disease are renal resistance to PTH and chondrodysplasia resulting from the constitutive inhibition of PTHR1/Gsa/AC/cAMP/PKA signaling. We developed a knock-in of the recurrent ACRDYS1 R368X PRKAR1A mutation in the mouse. No litters were obtained from [R368X]/[+] females (thus no homozygous [R368X]/[R368X] mice). In [R368X]/[+] mice, Western blot analysis confirmed mutant allele heterozygous expression. Growth retardation, peripheral acrodysostosis (including brachydactyly affecting all digits), and facial dysostosis were shown in [R368X]/[+] mice by weight curves and skeletal measurements (µCT scan) as a function of time. [R368X]/[+] male and female mice were similarly affected. Unexpected, however, whole-mount skeletal preparations revealed a striking delay in mineralization in newborn mutant mice, accompanied by a decrease in the height of terminal hypertrophic chondrocyte layer, an increase in the height of columnar proliferative prehypertrophic chondrocyte layer, and changes in the number and spatial arrangement of proliferating cell nuclear antigen (PCNA)-positive chondrocytes. Plasma PTH and basal urinary cAMP were significantly higher in [R368X]/[+] compared to WT mice. PTH injection increased urinary cAMP similarly in [R368X]/[+] and WT mice. PRKACA expression was regulated in a tissue (kidney not bone and liver) manner. This model, the first describing the germline expression of a PRKAR1A mutation causing dominant repression of cAMP-dependent PKA, reproduced the main features of ACRDYS1 in humans. It should help decipher the specificity of the cAMP/PKA signaling pathway, crucial for numerous stimuli. In addition, our results indicate that PRKAR1A, by tempering intracellular cAMP levels, is a molecular switch at the crossroads of signaling pathways regulating chondrocyte proliferation and differentiation. © 2016 American Society for Bone and Mineral Research.

Modulation of signaling through GPCR-cAMP-PKA pathways by PDE4 depends on stimulus intensity: Possible implications for the pathogenesis of acrodysostosis without hormone resistance.

In acrodysostosis without hormone resistance, a disease caused by phosphodiesterase (PDE)-4D mutations, increased PDE activity leads to bone developmental defects but with normal renal responses to PTH. To identify potential mechanisms for these disparate responses, we compared the effect of PDE activity on hormone signaling through the GPCR-Gsα-cAMP-PKA pathway in cells from two lineages, HEK-293 cells stably overexpressing PTH1R (HEKpthr) and human dermal fibroblasts, including studies evaluating cAMP levels using an Epac-based BRET-sensor for cAMP (CAMYEL). For ligand-induced responses inducing strong cAMP accumulation, the inhibition of PDE4 activity resulted in relatively small further increases. In contrast, when ligand-induced cAMP accumulation was of lesser intensity, the inhibition of PDE4 had a more pronounced effect. Similar results were obtained evaluating downstream events (cellular CREB phosphorylation and CRE-luciferase activity). Thus, the ability of PDE4 to modulate signaling through GPCR-cAMP-PKA pathways can depend on the cell type and stimulus intensity.

Clinical and Genetic Characterization of Tunisian Children with Hereditary 1,25-Dihydroxyvitamin D-Resistant Rickets.

BACKGROUND: Hereditary vitamin D-resistant rickets (HVDRR) is an autosomal recessive disorder characterized by the early onset of rickets and is caused by mutations in the vitamin D receptor (VDR) gene. Some HVDRR patients also have alopecia. PATIENTS AND METHODS: We retrospectively studied the clinical features, laboratory findings, genetic defects, as well as responses to treatment in a series of children with HVDRR. RESULTS: Eight patients from 7 families met the inclusion criteria. Alopecia was noted in 7 patients. Two different homozygous mutations in the VDR gene were identified in 6 patients: the p.K45E mutation located in the DNA-binding domain (5 patients with alopecia) and a novel p.T415R mutation located in the ligand-binding domain. A p.E143del CYP24A1 mutation, in the gene encoding the 25-hydroxyvitamin D3-24-hydroxylase, was identified in 2 brothers carrying the VDR gene mutation p.K45E. Six patients were treated with intermittent intravenous calcium treatment via the peripheral route with a clear improvement in 5 cases. CONCLUSION: To the best of our knowledge, this is the first major series reporting on HVDRR in Tunisia. The same mutation (p.K45E) was found in 5 apparently unrelated affected individuals. We have also extended the mutation spectrum by studying 1 novel VDR mutation.