Marie Bex

Spectrum and prevalence of FP/TMEM127 gene mutations in pheochromocytomas and paragangliomas.

CONTEXT Pheochromocytomas and paragangliomas are genetically heterogeneous neural crest-derived neoplasms. We recently identified germline mutations of the novel transmembrane-encoding gene FP/TMEM127 in familial and sporadic pheochromocytomas consistent with a tumor suppressor effect. OBJECTIVES To examine the prevalence and spectrum of FP/TMEM127 mutations in pheochromocytomas and paragangliomas and to test the effect of mutations in vitro. DESIGN, SETTING, AND PARTICIPANTS We sequenced the FP/TMEM127 gene in 990 individuals with pheochromocytomas and/or paragangliomas, including 898 previously unreported cases without mutations in other susceptibility genes from 8 independent worldwide referral centers between January 2009 and June 2010. A multiplex polymerase chain reaction-based method was developed to screen for large gene deletions in 545 of these samples. Confocal microscopy of 5 transfected mutant proteins was used to determine their subcellular localization. MAIN OUTCOME MEASURES The frequency and type of FP/TMEM127 mutation or deletion was assessed and correlated with clinical variables; the subcellular localization of 5 overexpressed mutants was compared with wild-type FP/TMEM127 protein. RESULTS We identified 19 potentially pathogenic FP/TMEM127 germline mutations in 20 independent families, but no large deletions were detected. All mutation carriers had adrenal tumors, including 7 bilateral (P = 2.7 × 10(-4)) and/or with familial disease (5 of 20 samples; P = .005). The median age at disease onset in the FP/TMEM127 mutation group was similar to that of patients without a mutation (41.5 vs 45 years, respectively; P = .54). The most common presentation was that of a single benign adrenal tumor in patients older than 40 years. Malignancy was seen in 1 mutation carrier (5%). Expression of 5 novel FP/TMEM127 mutations in cell lines revealed diffuse localization of the mutant proteins in contrast with the discrete multiorganelle distribution of wild-type TMEM127. CONCLUSIONS Germline mutations of FP/TMEM127 were associated with pheochromocytoma but not paraganglioma and occurred in an age group frequently excluded from genetic screening algorithms. Disease-associated mutations disrupt intracellular distribution of the FP/TMEM127 protein.

AcroBel – the Belgian registry on acromegaly: a survey of the ‘real-life’ outcome in 418 acromegalic subjects

OBJECTIVES To constitute a registry on acromegaly, AcroBel, to evaluate the epidemiology and quality of care of acromegaly in Belgium and Luxembourg. DESIGN A nationwide survey from June 2003 till September 2004 aiming to collect data from all patients with acromegaly who had visited the participating endocrine clinics after 1 January 2000. METHODS Retrospective data collection coupled to a visit within the survey period, allowing sampling of metabolic parameters and centralised determination of GH and IGF-I. RESULTS Four hundred and eighteen patients (51% men) were included, of which 96 were new cases, giving a mean incidence of 1.9 cases per million (c.p.m.) per year. The global prevalence was 41 c.p.m. but varied between 21 and 61 among different areas. Twenty-eight deaths were reported at a median age of 68 years in men and 74 years in women. The standardised mortality rate was significantly increased only in irradiated patients (2.70; confidence interval 1.60-4.55). Central measurements were available in 316 (75%) patients. Mean GH was < or = 2 microg/l in 65% and IGF-I was normal for age in 56%, while both criteria were fulfilled in 49%. Multimodal treatment was more effective than primary medical therapy, since 56.5% were controlled versus 24.3% (P < 0.0001). CONCLUSIONS AcroBel provides an excellent tool to analyse the prevalence, incidence, treatment modalities and outcome of acromegaly in Belgium. This real-life survey reveals that only half of acromegalic patients received an adequate therapy resulting in cure or disease control when stringent biochemical criteria are used.

Divergence between growth hormone and insulin-like growth factor-i concentrations in the follow-up of acromegaly.

CONTEXT Divergence between GH and IGF-I values is regularly observed in treated acromegalic patients, and its significance is unclear. OBJECTIVES The objective of the study was to explore the frequency and identify potential determinants of discordant serum GH and IGF-I concentrations in noncured acromegalic patients. PATIENTS Two hundred twenty-nine noncured acromegalic patients of the Belgian acromegaly registry (AcroBel) were grouped according to their mean GH level (< or = or > 2 microg/liter) and IGF-I z-score (< or = 2 or > 2). Clinical and metabolic parameters were compared between groups with active disease (high GH and IGF-I; n=81),high GH (with normal IGF-I; n=25), high IGF-I (with normal GH; n=55), and controlled disease (GH and IGF-I normal; n=68). RESULTS Compared with the high IGF-I group, the high GH group was characterized by younger age (52 vs. 58 yr, P < 0.05), female predominance (72 vs. 36%, P < 0.01), and lower body mass index (25 vs. 31 kg/m(2); P < 0.001), fasting glucose (91 vs. 99 mg/dl; P < 0.05), and glycated hemoglobin levels (5.7 vs. 6.1%; P < 0.01). There was no difference among the groups regarding baseline characteristics of pituitary adenoma, current medical treatment, or symptom score. CONCLUSIONS Thirty-five percent of noncured acromegalic patients exhibit a discordant GH and IGF-I pattern. The high GH phenotype was found predominantly in younger estrogen-sufficient females, implying a possible role for age, gender, and estrogens in this biochemical divergence. The high IGF-I phenotype was associated with a worse metabolic profile, suggesting that high IGF-I, rather than high GH, is indicative of persistently active disease.

The effects of growth hormone replacement therapy on bone metabolism in adult-onset growth hormone deficiency: a 2-year open randomized controlled multicenter trial.

Adult hypopituitary patients with growth hormone deficiency (GHD) show a significant decrease in bone mass and an increased fracture rate. Replacement therapy with GH increases bone turnover. Most of the long‐term data on bone mineral content (BMC) and bone mineral density (BMD) have been acquired in open, noncontrolled trials involving limited numbers of patients. To determine whether long‐term GH therapy is beneficial for bone despite the increased bone turnover, 100 patients (59 men and 41 women), aged 25‐65 years (mean, 49.7 years) with adult‐onset GHD were randomized to treatment with GH (40 men and 28 women; mean dose, 0.18 IU/kg per week) or to a nontreated control group (19 men and 13 women) for 24 months. Despite a similar increase in parameters of bone turnover (osteocalcin [OC], procollagen type I carboxy‐terminal propeptide [PICP], and pyridinolines ([PYD]) in male and female GH‐treated patients compared with controls, the effects on BMC and BMD as evaluated by dual‐energy X‐ray absorptiometry were gender specific. A significant increase in spine BMC and BMD and total hip BMD and a decrease in BMD at the ultradistal radius over time was observed in male GH‐treated patients compared with the evolution in controls (mean ± SEM change at 24 months: +6.8 ± 1.1% and p = 0.009, +5.1 ± 0.8% and p = 0.005, +3.5 ± 0.7% and p = 0.02, and −2.6 ± 0.8% and p = 0.008, respectively). No significant treatment effects were observed in female patients. Despite the increase in the total remodeling space induced by GH treatment, prolonged GH therapy in adult‐onset GHD has a positive effect on bone balance, maintaining bone mass in women, and even increasing it in men over a 2 year‐period.

Primary role of the HLA class II DRB1*0301 allele in Graves disease

The association of the Graves disease (GD) with HLA DR3 and DQA1*0501 in Caucasians has been described previously. From these studies it could not be determined whether one specific locus was primarily involved. Using a case-control study design, we have examined the role of HLA class II gene polymorphisms in the predisposition for GD in a group of Belgian subjects. We demonstrated that both DRB1*0301 and DQA1*0501 alleles conferred significant susceptibility in the DRB1*0301-DQA1*0501 haplotype. The DRB1*0301 allele was the primary susceptibility allele for GD, however, because the susceptibility provided by DQA1*0501 was most likely due to it being in linkage disequilibrium with DRB1*0301. The DRB1*0701/x and DQA1*0201/x genotypes and the DRB1*0701-DQA1*0201 haplotype provided protection with an equal RR of 0.29. Predictive value calculations showed that testing for DRB1*0301 gave the highest positive predictive value for GD in females and males. This was, however, 10 times higher in females and predicted a 3.63% risk for a random female to develop GD.

Effect of motilin on gastric emptying in patients with diabetic gastroparesis

Erythromycin markedly accelerates gastric emptying, possibly because it acts as a motilin agonist. In the present study, the effect of an equipotent dose of motilin was tested. In six patients with severe diabetic gastroparesis, gastric emptying of liquids and solids was examined scintigraphically after motilin or placebo in a double-blind crossover study. Motilin (10 pmol.kg-1.min-1) or saline was infused over a 90-minute period starting 5 minutes before breakfast. Motilin markedly accelerated emptying. For liquids, the half-emptying time was reduced from 51 +/- 6 to 22 +/- 11 minutes (P less than 0.01) and for solids from 111 +/- 4 to 51 +/- 12 minutes (P less than 0.01). The mean increase in plasma motilin levels was 1315 +/- 342 pg/mL, corresponding to an effective infusion rate of about 4 pmol.kg-1.min-1. In the control experiments, basal motilin levels (173 +/- 17 pg/mL) were within the normal range but increased steadily postprandially, reaching 321 +/- 25 pg/mL at the end of the study period, probably reflecting gastric distension. The postprandial increase in pancreatic polypeptide level was blunted compared with accepted normal values but was more pronounced during motilin infusion, i.e., 650 +/- 217 vs. 279 +/- 66 pg/mL (P less than 0.01), probably because of the improved emptying. Our data show that motilin accelerates gastric emptying in diabetic gastroparesis and support the hypothesis that erythromycins effect is mediated through motilin receptors.

A homozygous inactivating calcium-sensing receptor mutation, Pro339Thr, is associated with isolated primary hyperparathyroidism: correlation between location of mutations and severity of hypercalcaemia

Background  Inactivating mutations of the calcium‐sensing receptor (CaSR), a G‐protein‐coupled receptor with extracellular (ECD), transmembrane (TMD) and intracellular (ICD) domains, cause familial hypocalciuric hypercalcaemia, neonatal severe primary hyperparathyroidism and occasionally primary hyperparathyroidism in adults.

GNAS defects identified by stimulatory G protein alpha-subunit signalling studies in platelets.

CONTEXT GNAS is an imprinted region that gives rise to several transcripts, antisense transcripts, and noncoding RNAs, including transcription of RNA encoding the alpha-subunit of the stimulatory G protein (Gsalpha). The complexity of the GNAS cluster results in ubiquitous genomic imprints, tissue-specific Gsalpha expression, and multiple genotype-phenotype relationships. Phenotypes resulting from genetic and epigenetic abnormalities of the GNAS region include Albrights hereditary osteodystrophy, pseudohypoparathyroidism types Ia (PHPIa) and Ib (PHPIb), and pseudopseudohypoparathyroidism (PPHP). OBJECTIVE The aim was to study the complex GNAS pathology by a functional test as an alternative to the generally used but labor-intensive erythrocyte complementation assay. DESIGN AND PATIENTS We report the first platelet-based diagnostic test for Gsalpha hypofunction, supported by clinical, biochemical, and molecular data for six patients with PHPIa or PPHP and nine patients with PHPIb. The platelet test is based on the inhibition of platelet aggregation by cAMP, produced after Gsalpha stimulation. RESULTS Platelets are easily accessible, and platelet aggregation responses were found to reflect Gsalpha signaling defects in patients, in concordance with the patients phenotype and genotype. Gsalpha hypofunction in PHPIa and PPHP patients with GNAS mutations was clearly detected by this method. Mildly decreased or normal Gsalpha function was detected in patients with PHPIb with either an overall or exon 1A-only epigenetic defect, respectively. Platelet Gsalpha expression was reduced in both PHPIb patient groups, whereas XLalphas was up-regulated only in PHPIb patients with the broad epigenetic defect. CONCLUSION The platelet-based test is a novel tool for establishing the diagnosis of Gsalpha defects, which may otherwise be quite challenging.

Association of particular HLA class II alleles, haplotypes and genotypes with susceptibility to IDDM in the Belgian population.

SummaryUsing a highly discriminatory DNA typing technique, based on the polymerase chain reaction and reverse dot blot hybridization, more refined results were obtained on the association of particular HLA class II alleles, haplotypes and genotypes with insulin-dependent diabetes mellitus in the Belgian population. The previously reported predisposing effect for the DRB1*0301 encoded DR3 serologic specificity was confirmed and could be assigned to the DRB3*0200 encoded DR52b serologic specificity. A second high risk haplotype, DRB1*0401-DQB1*0302 encoding the DR4-DQ8 serologic specificity, accounted for increased susceptibility both in the total insulin-dependent diabetic population and among DR4-positive patients. Moreover, we found that these DR4 associated DRB1 and DQB1 alleles act as independent risk factors. A possible role for the DPB1 locus can be rejected since the observed predisposing effect for DPB1*0202 probably occurred due to linkage disequilibrium of this allele with DRB1*0301. Particular extended haplotypes accounted for the decreased relative risk observed for the DR2, DR11 and DR13 serologic specificities. The highest relative risk was observed for those DQA1/DQB1 genotypes, allowing for the formation of 4SS (DQαArg52+/DQΒAsp57−) heterodimers.

Paroxysmal Nonkinesigenic Dyskinesias due to Recurrent Hypoglycemia Caused by an Insulinoma

Paroxysmal dyskinesias are characterized by recurrent attacks of dystonic, choreatic, or ballistic movements. They can be sporadic or inherited and are classified traditionally into three subtypes. Paroxysmal kinesigenic dyskinesias (PKD) typically present with brief (seconds to minutes) dyskinetic episodes triggered by sudden movements. Attacks of paroxysmal exertional dyskinesias (PED) are provoked by prolonged physical exercise and typically last between 5 min and 2 h. Paroxysmal nonkinesigenic dyskinesias (PNKD) usually last from 5 min to 4 h, are not induced by movement or exercise but sometimes by fatigue, alcohol or caffeine. The distinction between sporadic PNKD and psychogenic movement disorders is often difficult. Recently, several groups including ours identified mutations in the glucose transporter of the blood brain barrier, GLUT1, as a cause of familial PED. These mutations decrease the ability of GLUT1 to transport glucose, leading to a reduced cerebrospinal fluid (CSF)/serum glucose ratio. Here, we describe a patient with sporadic PNKD due to recurrent hypoglycemia caused by an insulinoma. This further strengthens the emerging connection between paroxysmal dyskinesias and disturbed brain glucose homeostasis. A 39-year-old woman was admitted to the emergency department because of involuntary movements of arms and legs with acute onset. On admission, there were random, nonrhythmic, nonsynchronous movements of arms and legs, which clinically seemed to be choreatic and ballistic rather than epileptic in nature. Clinical examination revealed no other significant abnormalities. In particular, consciousness and orientation were normal. Approximately 1 h after onset the dyskinesias ceased spontaneously. The patient reported approximately five similar dyskinetic episodes over the preceding 2 yr, each lasting approximately 30 min. Consciousness was always preserved although she sometimes felt ‘‘dreamy’’ during attacks. There was no amnesia. Apart from psychological stress and fatigue, she identified no provoking factors. Her medical history was otherwise unremarkable. She occasionally took ibuprofen for left arm pain. She denied any substance abuse. She had no family history of neurological disorders. Blood sampling 10 min after admission revealed hypoglycemia (42 mg/dL; normal: 55–100 mg/dL) and insulin (5 mU/L) and C-peptide (0.57 nmol/L) levels that were inappropriately high for the degree of hypoglycemia, but no other abnormalities. Toxicological urine screening, cranial CT and MRI were normal. EEG on the following day was normal except for a slight excess in beta activity. Daily controls also revealed frequent asymptomatic hypoglycemic episodes (with glucose levels as low as 35 mg/dL). The CSF/serum glucose ratio after overnight fasting was normal (0.64; CSF glucose: 34 mg/dL; serum glucose: 53 mg/dL). Abdominal CT and endoscopic ultrasound visualised a 0.7-cm diameter lesion in the pancreatic tail. After laparoscopic enucleation the suspected diagnosis of an insulinoma was confirmed pathologically. No more hypoglycemic and dyskinetic attacks occurred in the 12 months between insulinoma removal and manuscript submission. Our patient suffered from sporadic PNKD, which resolved after removal of an insulinoma. Although dyskinesia during hypoglycemia has been described, it is an uncommon manifestation of hypoglycemia compared with typical neuroglycopenic symptoms such as confusion, behavioural changes, dizziness, weakness, loss of consciousness, seizures, and amnesia. Reports of paroxysmal dyskinesias caused by recurrent hypoglycemia are scarce. Marsden and coworkers described a patient with a suspected insulinoma who adopted dystonic postures when recovering from hypoglycemic episodes. To our knowledge, there have been only two published reports of patients with paroxysmal dyskinesias, a pathologically confirmed insulinoma and documented remission of the attacks following insulinoma removal. In one of these two cases the patient had a structural lesion in the globus pallidus, which may have contributed to the dyskinesias. In both published cases, however, the patient had typical PED, whereas our patient had PNKD. Our findings suggest that the possibility of an insulinoma should be considered in every patient with sporadic PNKD, especially since insulinomas are often curable. Interestingly, our patient also had documented hypoglycemic episodes without dyskinesias, consistent with the known lack of a tight correlation between plasma glucose levels and hypoglycemic neurological symptoms in general. Adequate glucose delivery to the brain does not only depend on plasma glucose levels, but also on efficient glucose transport across the blood brain barrier. The latter process is impaired by GLUT1 mutations, a recently identified cause of familial PED. Thus, recurrent shortage of glucose supply to the brain may represent a common mechanism underlying several subtypes of paroxysmal dyskinesias, including familial PED, sporadic PED, and sporadic PNKD.