Treatment switches of disease-modifying therapies in people with multiple sclerosis: long-term experience from the German MS Registry.

Background: The spectrum of disease-modifying therapies (DMTs) for people with multiple sclerosis (PwMS) has expanded over years, but data on treatment strategies is largely lacking. DMT switches are common clinical practice. Objective: To compare switchers and non-switchers, characterize the first DMT switch and identify reasons and predictors for switching the first DMT. Methods: Data on 2722 PwMS from the German MS Registry were retrospectively analyzed regarding sociodemographic/clinical differences between 1361 switchers (PwMS discontinuing the first DMT) and non-switchers matched according to age, sex, and observation period. Frequencies of first and second DMTs were calculated and switch reasons identified. Predictors for DMT switches were revealed using univariable and multivariable regression models. Results: Switchers and non-switchers differed significantly regarding time to first DMT, education, calendar period of the first DMT start (2014-2017 versus 2018-2021), first DMT class used [mild-to-moderate efficacy (MME) versus high-efficacy (HE) DMT], time on first DMT, and disease activity at first DMT start or cessation/last follow-up. The majority of PwMS started with MME DMTs (77.1%), with the most common being glatiramer acetate, dimethyl/diroximel fumarate, and beta-interferon variants. Switchers changed treatment more often to HE DMTs (39.6%), most commonly sphingosine-1-phosphate receptor modulators, anti-CD20 monoclonal antibodies, and natalizumab. Fewer PwMS switched to MME DMTs (35.9%), with the most common being dimethyl/diroximel fumarate, teriflunomide, or beta-interferon. Among 1045 PwMS with sufficient data (76.8% of 1361 switchers), the most frequent reasons for discontinuing the first DMT were disease activity despite DMT (63.1%), adverse events (17.1%), and patient request (8.3%). Predictors for the first DMT switch were MME DMT as initial treatment [odds ratio (OR) = 2.83 (1.76-4.61), p < 0.001; reference: HE DMT], first DMT initiation between 2014 and 2017 [OR = 11.55 (6.93-19.94), p < 0.001; reference: 2018-2021], and shorter time on first DMT [OR = 0.22 (0.18-0.27), p < 0.001]. Conclusion: The initial use of MME DMTs was among the strongest predictors of DMT discontinuation in a large German retrospective MS cohort, arguing for the need for prospective treatment strategy trials, not only but also on the initial broad use of HE DMTs in PwMS.

Occurrence and Risk Factors of Relapse Activity after Vaccination against COVID-19 in People with Multiple Sclerosis: 1-Year Follow-Up Results from a Nationwide Longitudinal Observational Study.

Several studies reported post-SARS-CoV-2-vaccination (PV) symptoms. Even people with multiple sclerosis (PwMS) have concerns about disease activity following the SARS-CoV-2 vaccination. We aimed to determine the proportion of PwMS with PV relapses, the PV annualized relapse rate (ARR), the time from vaccination to subsequent relapses, and identify sociodemographic/clinical risk factors for PV relapses. PwMS were surveyed several times at baseline and four follow-ups as part of a longitudinal observational study regarding the safety and tolerability of the SARS-CoV-2 vaccination. The inclusion criteria for this analysis were age ≥18 years, ≥1 SARS-CoV-2 vaccination, and ≥1-year observation period since initial vaccination. Of 2466 PwMS, 13.8% reported PV relapses (mostly after second [N = 147] or booster vaccination [N = 145]) at a median of 8.0 (first/third quantile: 3.55/18.1) weeks PV, with the shortest period following initial vaccination (3.95 weeks). The ARR was 0.153 (95% confidence interval: 0.138-0.168), with a median observation period since initial vaccination of 1.2 years. Risk factors for PV relapses were younger age, female gender, moderate-severe disability levels, concurrent autoimmune diseases, relapsing-remitting MS courses, no DMT, and relapses within the year prior to the first vaccination. Patients' health conditions before/during initial vaccination may play a more important role in PV relapse occurrence than vaccination per se.

There's an App for it: A systematic review of mobile apps providing information about abortion using a revised MARS scale.

Mobile applications (apps) are increasingly being used to access health-related information, but it may be challenging for consumers to identify accurate and reliable platforms. We conducted a systematic review of applications that provide information about abortion. We searched the iTunes and Google Play stores and queried professional networks to identify relevant apps. To evaluate the apps, we used the validated Mobile App Rating Scale (MARS) and added relevant abortion-specific elements. Two reviewers independently rated each app, and we report mean scores on a 5-point scale across the domains of engagement, functionality, esthetics, and information. We also rated app characteristics (including target population and reach), and number of desirable abortion-specific features. We defined recommended apps as those that achieved a score of 4.0 or above for the question: "would you recommend this app to people who may benefit from it?" Our search initially yielded 282 apps and we identified two additional apps through professional mailing lists. Most were irrelevant or not abortion-specific. We excluded 37 apps that sought to discourage users from seeking abortion. Only 10 apps met inclusion criteria for this review. The Euki app had the highest overall score (4.0). Half of the apps achieved a score of 3.0 or greater. Most of the apps had few desirable design features. Some apps provided significant information but had poor functionality. Only four apps met criteria for being recommended: Euki, Safe Abortion by Hesperian, Ipas Mexico, and Marie Stopes Mexico. In conclusion, we found few apps that provide unbiased information about abortion, and their quality varied greatly. App developers and abortion experts should consider designing additional apps that are clinically accurate, unbiased and well-functioning. We registered this review in the PROSPERO database (Registration # CRD42020195802).

Frequency and Predictors of Relapses following SARS-CoV-2 Vaccination in Patients with Multiple Sclerosis: Interim Results from a Longitudinal Observational Study.

Despite protection from severe COVID-19 courses through vaccinations, some people with multiple sclerosis (PwMS) are vaccination-hesitant due to fear of post-vaccination side effects/increased disease activity. The aim was to reveal the frequency and predictors of post-SARS-CoV-2-vaccination relapses in PwMS. This prospective, observational study was conducted as a longitudinal Germany-wide online survey (baseline survey and two follow-ups). Inclusion criteria were age ≥18 years, MS diagnosis, and ≥1 SARS-CoV-2 vaccination. Patient-reported data included socio-demographics, MS-related data, and post-vaccination phenomena. Annualized relapse rates (ARRs) of the study cohort and reference cohorts from the German MS Registry were compared pre- and post-vaccination. Post-vaccination relapses were reported by 9.3% PwMS (247/2661). The study cohort's post-vaccination ARR was 0.189 (95% CI: 0.167-0.213). The ARR of a matched unvaccinated reference group from 2020 was 0.147 (0.129-0.167). Another reference cohort of vaccinated PwMS showed no indication of increased post-vaccination relapse activity (0.116; 0.088-0.151) compared to pre-vaccination (0.109; 0.084-0.138). Predictors of post-vaccination relapses (study cohort) were missing immunotherapy (OR = 2.09; 1.55-2.79; p < 0.001) and shorter time from the last pre-vaccination relapse to the first vaccination (OR = 0.87; 0.83-0.91; p < 0.001). Data on disease activity of the study cohort in the temporal context are expected for the third follow-up.

SARS-CoV-2 vaccination in patients with multiple sclerosis in Germany and the United Kingdom: Gender-specific results from a longitudinal observational study.

Background: Vaccines offer people with multiple sclerosis (PwMS) an effective protection against severe COVID-19 disease courses. However, representative real-world data on the tolerability of SARS-CoV-2 vaccines in PwMS are limited. We aimed at analysing vaccination reactions (VRs) and MS deterioration following SARS-CoV-2 vaccinations in German and United Kingdom (UK) PwMS, especially regarding gender-specific differences. Methods: The German Multiple Sclerosis Society and the UK MS Registry acquired health data via an online system following the first (X1) and second SARS-CoV-2 vaccination (X2), respectively: sociodemographic and clinical data, vaccines used, VRs, MS deterioration (worsened or new MS symptoms, Germany only) and relapses (Germany only). The frequencies of VRs and MS deterioration were analysed stratified by gender. Findings: Following X1 (X2), 2346 (1835) German PwMS and 3796 (683) UK PwMS participated in the study. The most frequent vaccination scheme was two-dose tozinameran for Germany (77·1%, 1424/1847) and two-dose AZD1222 for the UK (61·3%, 419/683). The most common VRs were fatigue, headache and pain (at the injection site) and occurred more often in women compared with men. German PwMS reported VRs more frequently after X2 vs. X1 (65·4% [1201/1835] vs. 61·2% [1435/2346]), while for UK patients it was the opposite (X1 vs. X2: 48·7% [1849/3796] vs. 30·0% [205/683]). MS deterioration occurred in 19·0% (445/2346) of the German PwMS without resulting in gender-specific differences. Fatigue and gait impairment were the most frequent deteriorated MS symptoms. Interpretation: Female PwMS reported experiencing VRs more often than men. Longitudinal data are needed to enable valid statements regarding long-term MS deterioration and long-lasting VRs. Funding: German Multiple Sclerosis Society (DMSG Bundesverband e.V.), Biogen, Bristol Myers Squibb, Merck Serono, Mylan, Novartis, Roche and Sanofi.

Trends in administrative prevalence of multiple sclerosis and utilization patterns of disease modifying drugs in Germany.

BACKGROUND: This study aimed to describe recent developments of multiple sclerosis (MS) prevalence in Germany and to assess utilization patterns of disease-modifying drugs (DMDs). METHODS: We used nationwide outpatient claims data of the statutory health insurance (SHI) from the years 2012 to 2019, covering 87% of the total German population. In annual cross-sectional analyses, MS prevalence was measured as the percentage of the SHI population affected by MS. Annual agent-specific prescription prevalence of DMDs was calculated by the number of patients receiving the DMD per 1.000 MS patients. RESULTS: From 2012 to 2019, the prevalence of MS increased gradually from 0.27% to 0.34%. The overall DMD prescription prevalence in MS patients rose from 436 per 1,000 MS patients (2012) to 483 (2019). From 2012 to 2019 the prescription prevalence of interferon-beta 1a and interferon-beta 1b decreased sharply from 180.2 to 70.8 (-61%) and 80.2 to 34.1 (-57%), respectively. In contrast, the prescription prevalence of teriflunomide (2012: 8.5; 2019: 54.5) and fingolimod (2012: 28.5; 2019: 63.8) exhibited a pronounced increase by factors of 5.4 and 2.2, respectively. CONCLUSION: MS prevalence in Germany steadily increased in recent years. MS treatment patterns changed markedly indicating a shifting predominance of DMD injectable drugs to oral medications.

Treatment patterns in pediatric patients with multiple sclerosis in Germany-a nationwide claim-based analysis.

BACKGROUND: The manifestation of multiple sclerosis (MS) in childhood and adolescence occurs in 3%-5% of all MS cases. However, the immunomodulatory and symptomatic treatment options in this population group are still limited. OBJECTIVE: We aimed to elucidate the prescription frequency of medications used in pediatric patients with multiple sclerosis (PwMS) compared with the general population, considering the entire spectrum of medications prescribed. METHODS: Based on nationwide outpatient drug prescription data and statutory health insurance (SHI) physicians' claims data from 2018, we conducted a population-based cross-sectional study in Germany. Children and adolescents aged ⩽17 years (n = 11,381,939) diagnosed with MS (n = 613), and a matched (age, sex, and health insurance sector) control group (n = 6130) were included. The prescription prevalence was measured as the proportion of MS patients with ⩾1 prescription. RESULTS: Of the 613 pediatric PwMS with a median age of 16 years, 403 (65.7%) were female. For 15 out of the 18 different active agents analyzed, PwMS had a significantly higher prescription prevalence than the control group (Fisher's exact test: p ⩽ 0.037). The most frequently prescribed drugs in PwMS were ibuprofen (28.4%; anti-inflammatory drug), cholecalciferol (23.0%; vitamin D3), and interferon beta-1a (21.5%; disease-modifying drug, DMD). The proportions of DMD prescriptions and antibiotic prescriptions were higher among PwMS aged 15-17 years than among those ⩽14 years (DMD: 43.4% vs 34.2%, p = 0.05; antibiotic: 34.1% vs 24.8%, p = 0.031). In contrast, younger PwMS were more likely to receive a prescription for anti-inflammatory/anti-rheumatic drugs (36.6% vs 26.5%, p = 0.02). CONCLUSION: Our study analyzing real-world medication data showed that interferon beta, anti-inflammatory drugs, and vitamins play an essential role in the treatment of pediatric PwMS. Future research should evaluate longitudinal treatment patterns of pediatric PwMS, paying particular attention to the time of diagnosis, time of first DMD initiation, and therapy switches.

Prevalence of pediatric multiple sclerosis in Germany: A nationwide population-based analysis.

BACKGROUND AND PURPOSE: Prevalence data are needed to reveal trends regarding the pediatric multiple sclerosis (MS) situation worldwide. The aim was to identify changes in MS diagnosis prevalence in pediatric patients over a 10-year period in Germany. METHODS: This analysis is based on nationwide outpatient claims data of children aged <18 years covered by the German statutory health insurance (n = 11,381,939 in 2018). People with MS (PwMS) had ≥1 documented MS diagnosis (International Classification of Diseases, 10th Revision, German modification code G35.x). The annual pediatric MS diagnosis prevalence was analyzed regarding age, sex, and place of residence during 2009-2018. RESULTS: The prevalence of pediatric MS developed from 5.3 (2009) to 5.4 (2018)/100,000 insured population aged <18 years. The MS prevalence in patients aged 15-17 years showed a moderate increase over 10 years (19.6-22.7/100,000), whereas patients ≤14 years old showed a slight decrease (1.9-1.7/100,000). The sex ratio (female:male) in 2018 was relatively balanced in PwMS aged ≤14 years (1.32) but female-dominated in those aged 15-17 years (2.47). The formerly different prevalence of pediatric MS between East and West Germany has converged since 2012. CONCLUSIONS: So far, this is the largest study of pediatric MS prevalence in terms of source population size (87% of German children <18 years of age, n = 11,381,939 in 2018) and study period (2009-2018) worldwide. The analyses revealed an increase in MS prevalence and a female-dominated sex ratio in "older" adolescents compared to younger patients.

1-800-Externship: The Use of Hotlines as a Training Modality for Future Clinicians.

Mental health on college campuses is a growing issue. Despite a rise in demand for services, counseling centers generally offer assistance during business hours, with a limited number of clinicians. Hotlines can provide an avenue for suicide prevention and intervention while offering training to graduate counseling students. The present study used a qualitative approach to examine the benefits and challenges of using hotlines as a clinical training modality. Interviews with nine graduate students volunteering at a hotline were analyzed using a consensual qualitative research methodology. Several domains were identified, including: three domains related to initial involvement with a clinical training experience at a hotline, four related to the experience of volunteering, and five related to the connection of the clinical training experience to the participant's development as a clinician. Hotlines as a training modality can be used to benefit the community and contribute to the development of future clinicians.

Which visibility indicators best represent a population's preference for a level of visual air quality?

Several studies have been carried out over the past 20 or so years to assess the level of visual air quality that is judged to be acceptable in urban settings. Groups of individuals were shown slides or computer-projected scenes under a variety of haze conditions and asked to judge whether each image represented acceptable visual air quality. The goal was to assess the level of haziness found to be acceptable for purposes of setting an urban visibility regulatory standard. More recently, similar studies were carried out in Beijing, China, and the more pristine Grand Canyon National Park and Great Gulf Wilderness. The studies clearly showed that when preference ratings were compared to measures of atmospheric haze such as atmospheric extinction, visual range, or deciview (dv), there was not a single indicator that represented acceptable levels of visual air quality for the varied urban or more remote settings. For instance, using a Washington, D.C., setting, 50% of the observers rated the landscape feature as not having acceptable visual air quality at an extinction of 0.19 km-1 (21 km visual range, 29 dv), while the 50% acceptability point for a Denver, Colorado, setting was 0.075 km-1 (52 km visual range, 20 dv) and for the Grand Canyon it was 0.023 km-1 (170 km visual range, 7 dv). Over the past three or four decades, many scene-specific visibility indices have been put forth as potential indicators of visibility levels as perceived by human observers. They include, but are not limited to, color and achromatic contrast of single landscape features, average and equivalent contrast of the entire image, edge detection algorithms such as the Sobel index, and just-noticeable difference or change indexes. This paper explores various scene-specific visual air quality indices and examines their applicability for use in quantifying visibility preference levels and judgments of visual air quality. Implications: Visibility acceptability studies clearly show that visibility become more unacceptable as haze increases. However, there are large variations in the preference levels for different scenes when universal haze indicators, such as atmospheric extinction, are used. This variability is significantly reduced when the sky-landscape contrast of the more distant landscape features in the observed scene is used. Analysis suggest that about 50% of individuals would find the visibility unacceptable if at any time the more distant landscape features nearly disappear, that is, they are at the visual range. This common metric could form the basis for setting an urban visibility standard.

Perinatal management of a preterm neonate affected by hyperprostaglandin E2 syndrome (HPS).

BACKGROUND: Neonates affected by hyperprostaglandin E(2) syndrome (HPS) present with severe polyuria. Both urinary losses as well as prostaglandin synthesis inhibitors may precipitate acute renal failure (ARF). AIM: Our goal was to maintain euvolaemia by replacement of urinary losses. PATIENT: Our patient was born prematurely with a family history typical of HPS. Urinary salt and water losses and PGE(2) excretion were determined in 2- to 4-h intervals. Salt and water were replaced accordingly. RESULTS: Within the first 48 h, urinary losses and PGE(2) increased continuously to 50 ml/kg/h and 374 ng/h/1.73 m(2), respectively. Following exposure to 0.05-0.5 mg/kg/d indomethacin, urinary output decreased steadily to 10-15/ml/kg/h. CONCLUSION: In euvolaemic preterm neonates with HPS and the need for excessive replacement of salt and water, inhibition of renal PGE(2) excretion with indomethacin effectively reduces polyuria and natriuresis without acutely compromising renal function.

Impact of tele-advice on community nurses' knowledge of venous leg ulcer care.

AIM: This paper reports a study assessing the impact of the provision of expert tele-advice to community nurses in enhancing their knowledge of leg ulcer care. BACKGROUND: Community nurses have traditionally been responsible for the care of patients with leg ulcers. However, access to expert medical and nursing advice has been restricted to the local hospital environment. The introduction of e-health and telemedicine have created opportunities to provide online and immediate access to wound care expertise from centres of excellence to primary health care staff in managing patients' wounds in their own home. METHOD: A stratified randomized controlled trial was used to examine community nurses' knowledge before and after the provision of expert tele-advice. A knowledge measurement tool comprised of 40 multiple-choice questions was adopted, with correct responses identified by a panel of wound care experts. The questions covered the three themes of dressings, management and physiology, with different levels of difficulty categorized as easy, medium or difficult. The tool was administered before and after the intervention (12 weeks) to both the experimental and control groups. RESULTS: Statistically significant improvements were observed only for the experimental group in the areas of dressings and management, as well as in the medium level questions. No statistically significant improvement was seen for the easy questions, as there was little room for improvement because of preintervention high scores. For the difficult questions, it was thought that more time would be needed for a more positive outcome. CONCLUSIONS: The results suggest that tele-advice can be of great benefit to community nurses in enhancing their knowledge in the practice of leg ulcer care. This will have significant implications for more efficient use of human resources and cost effectiveness in wound care.

Salt handling in the distal nephron: lessons learned from inherited human disorders.

The molecular basis of inherited salt-losing tubular disorders with secondary hypokalemia has become much clearer in the past two decades. Two distinct segments along the nephron turned out to be affected, the thick ascending limb of Henle's loop and the distal convoluted tubule, accounting for two major clinical phenotypes, hyperprostaglandin E syndrome and Bartter-Gitelman syndrome. To date, inactivating mutations have been detected in six different genes encoding for proteins involved in renal transepithelial salt transport. Careful examination of genetically defined patients ("human knockouts") allowed us to determine the individual role of a specific protein and its contribution to the overall process of renal salt reabsorption. The recent generation of several genetically engineered mouse models that are deficient in orthologous genes further enabled us to compare the human phenotype with the animal models, revealing some unexpected interspecies differences. As the first line treatment in hyperprostaglandin E syndrome includes cyclooxygenase inhibitors, we propose some hypotheses about the mysterious role of PGE(2) in the etiology of renal salt-losing disorders.

Classification and rescue of ROMK mutations underlying hyperprostaglandin E syndrome/antenatal Bartter syndrome.

BACKGROUND: Mutations in the renal K+ channel ROMK (Kir 1.1) cause hyperprostaglandin E syndrome/antenatal Bartter syndrome (HPS/aBS), a severe tubular disorder leading to renal salt and water wasting. Several studies confirmed the predominance of alterations of current properties in ROMK mutants. However, in most of these studies, analysis was restricted to nonmammalian cells and electrophysiologic methods. Therefore, for the majority of ROMK mutations, disturbances in protein trafficking remained unclear. The aim of the present study was the evaluation of different pathogenic mechanisms of 20 naturally occurring ROMK mutations with consecutive classification into mutational classes and identification of distinct rescue mechanisms according to the underlying defect. METHODS: Mutated ROMK potassium channels were expressed in Xenopus oocytes and a human kidney cell line and analyzed by two electrode voltage clamp analysis, immunofluorescence, and Western blot analysis. RESULTS: We identified 14 out of 20 ROMK mutations that did not reach the cell surface, indicating defective membrane trafficking. High expression levels rescued six out of 14 ROMK mutants, leading to significant K+ currents. In addition, two early inframe stop mutations could be rescued by aminoglycosides, resulting in full-length ROMK and correct trafficking to the plasma membrane in a subset of transfected cells. CONCLUSION: In contrast to previous reports, most of the investigated ROMK mutations displayed a trafficking defect that might be rescued by pharmacologic agents acting as molecular chaperones. The evaluation of different disease-causing mechanisms will be essential for establishing new and more specific therapeutic strategies for HPS/aBS patients.

Hereditary Hypokalemic Salt-losing Tubular Disorders.

The inherited hypokalemic tubular disorders are frequently summarized under the heading "Bartter syndrome" since they shareseveral clinical and biochemical findings such as renal salt wasting, hypokalemic metabolic alkalosis, normal blood pressure despite hypereninemic hyperaldosteronism and hyperplasia of the juxtaglomerular apparatus. However, careful characterization of the clinical phenotype and the correlation with the underlying molecular basis justifies the differentiation into at least four distinct disease entities: (i) the hyperprostaglandin E syndrome or antenatal variant of Bartter syndrome (HPS/aBS), which is caused by mutations in either the Na-K-2Cl cotransporter or the potassium channel of the medullary thick ascending limb of Henle's loop; (ii) the HPS/aBS with sensorineural deafness which results from inactivating mutations in the Barttin beta-subunit of the renal chloride channels; (iii) the classic Bartter syndrome caused by mutations in the chloride channel of the distal nephron; and (iv) Gitelman's variant of Bartter syndrome which is caused by mutations of the Na-Cl cotransporter of the distal convoluted tubule. This review will summarize the clinical characteristics of these diseases and the progress recently made in the identification of the underlying molecular defects that will hopefully add to the current knowledge of the pathogenesis of these diseases.

Barttin increases surface expression and changes current properties of ClC-K channels.

The term Bartter syndrome encompasses a heterogeneous group of autosomal recessive salt-losing nephropathies that are caused by disturbed transepithelial sodium chloride reabsorption in the distal nephron. Mutations have been identified in the NKCC2 (Na(+)-K(+)-2Cl(-)) cotransporter and ROMK potassium channel, which cooperate in the process of apical sodium chloride uptake, and ClC-Kb chloride channels, which mediate basolateral chloride release. Recently, mutations in barttin, a protein not related to any known ion transporter or channel, were described in BSND, a variant of Bartter syndrome associated with sensorineural deafness. Here we show that barttin functions as an activator of ClC-K chloride channels. Expression of barttin together with ClC-K in Xenopus oocytes increased ClC-K current amplitude, changed ClC-K biophysical properties, and enhanced ClC-K abundance in the cell membrane. Co-immunoprecipitation revealed a direct interaction of barttin with ClC-K. We performed in situ hybridization on rat kidney slices and RT-PCR analysis on microdissected nephron segments to prove co-expression of barttin, ClC-K1 and ClC-K2 along the distal nephron. Functional analysis of BSND-associated point mutations revealed impaired ClC-K activation by barttin. The results demonstrate regulation of a CLC chloride channel by an accessory protein and indicate that ClC-K activation by barttin is required for adequate tubular salt reabsorption.

Hypomagnesemia with secondary hypocalcemia is caused by mutations in TRPM6, a new member of the TRPM gene family.

Magnesium is an essential ion involved in many biochemical and physiological processes. Homeostasis of magnesium levels is tightly regulated and depends on the balance between intestinal absorption and renal excretion. However, little is known about specific proteins mediating transepithelial magnesium transport. Using a positional candidate gene approach, we identified mutations in TRPM6 (also known as CHAK2), encoding TRPM6, in autosomal-recessive hypomagnesemia with secondary hypocalcemia (HSH, OMIM 602014), previously mapped to chromosome 9q22 (ref. 3). The TRPM6 protein is a new member of the long transient receptor potential channel (TRPM) family and is highly similar to TRPM7 (also known as TRP-PLIK), a bifunctional protein that combines calcium- and magnesium-permeable cation channel properties with protein kinase activity. TRPM6 is expressed in intestinal epithelia and kidney tubules. These findings indicate that TRPM6 is crucial for magnesium homeostasis and implicate a TRPM family member in human disease.

Clinical presentation of genetically defined patients with hypokalemic salt-losing tubulopathies.

PURPOSE: Hypokalemic salt-losing tubulopathies (Bartter-like syndromes) comprise a set of clinically and genetically distinct inherited renal disorders. Mutations in four renal membrane proteins involved in electrolyte reabsorption have been identified in these disorders: the furosemide-sensitive sodium-potassium-chloride cotransporter NKCC2, the potassium channel ROMK, the chloride channel ClC-Kb, and the thiazide-sensitive sodium-chloride cotransporter NCCT. The aim of this study was to characterize the clinical features associated with each mutation in a large cohort of genetically defined patients. PATIENTS AND METHODS: The phenotypic characteristics of 65 patients with molecular defects in NKCC2, ROMK, ClC-Kb, or NCCT were collected retrospectively. RESULTS: ROMK and NKCC2 patients presented with polyhydramnios, nephrocalcinosis, and hypo- or isosthenuria. Hypokalemia was less severe in the ROMK patients compared with the NKCC2 patients. In contrast, NCCT patients had hypocalciuria, hypomagnesemia, and marked hypokalemia. While this dissociation of renal calcium and magnesium handling was also observed in some ClC-Kb patients, a few ClC-Kb patients presented with hypercalciuria and hypo- or isosthenuria. CONCLUSIONS: ROMK, NKCC2, and NCCT mutations usually have uniform clinical presentations, whereas mutations in ClC-Kb occasionally lead to phenotypic overlaps with the NCCT or, less commonly, with the ROMK/NKCC2 cohort. Based on these results, we propose an algorithm for the molecular diagnosis of hypokalemic salt-losing tubulopathies.

Primary gene structure and expression studies of rodent paracellin-1.

The novel member of the claudin multigene family, paracellin-1/claudin-16, encoded by the gene PCLN1, is a renal tight junction protein that is involved in the paracellular transport of magnesium and calcium in the thick ascending limb of Henle's loop. Mutations in human PCLN1 are associated with familial hypomagnesemia with hypercalciuria and nephrocalcinosis, an autosomal recessive disease that is characterized by severe renal magnesium and calcium loss. The complete coding sequences of mouse and rat Pcln1 and the murine genomic structure are here presented. Full-length cDNAs are 939 and 1514 bp in length in mouse and rat, respectively, encoding a putative open-reading frame of 235 amino acids in both species with 99% identity. Exon-intron analysis of the human and mouse genes revealed a 100% homology of coding exon lengths and splice-site loci. By radiation hybrid mapping, the murine Pcln1 gene was assigned directly to marker D16Mit133 on mouse chromosome 16 (syntenic to a locus on human chromosome 3q27, which harbors the human PCLN1 gene). Mouse multiple-tissue Northern blot showed Pcln1 expression exclusively in the kidney. The expression profile along the nephron was analyzed by reverse transcriptase-PCR on microdissected nephron segments and immunohistochemistry of rat kidney. Paracellin-1 expression was restricted to distal tubular segments including the thick ascending limb of Henle's loop, the distal tubule, and the collecting duct. The identification and characterization of the rodent Pcln1 genes provide the basis for further studies of paracellin-1 function in suitable animal models.

Novel paracellin-1 mutations in 25 families with familial hypomagnesemia with hypercalciuria and nephrocalcinosis.

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is an autosomal recessive tubular disorder that is frequently associated with progressive renal failure. The primary defect is related to impaired tubular reabsorption of magnesium and calcium in the thick ascending limb of Henle's loop. Mutations in PCLN-1, which encodes the renal tight junction protein paracellin-1 (claudin-16), were identified as the underlying genetic defects. Comprehensive clinical data and the results of PCLN-1 mutation analysis of 25 FHHNC families with 33 affected individuals are presented. Patients presented mainly with urinary tract infections, polyuria, and hematuria at a median age of 3.5 yr. At the time of diagnosis, the GFR was already decreased to <60 ml/min per 1.73 m(2) for 11 patients. Twelve patients exhibited progression to end-stage renal disease, at a median age of 14.5 yr. Treatment with magnesium salts and thiazides seemed to have no effect on the progression of the disease. Genotype analysis revealed PCLN-1 mutations in all except three mutant alleles (94%). Fifteen different mutations were observed, including eight novel mutations. The accumulation of mutations affecting the first extracellular loop was striking, with 48% of all mutant alleles exhibiting a Leu151Phe exchange. Haplotype analysis strongly suggested a founder effect among patients with FHHNC who originated from Germany or eastern European countries. In 13 of 23 families, hypercalciuria and/or nephrolithiasis were observed in otherwise unaffected family members, indicating a possible role of heterozygous PCLN-1 mutations in yielding hypercalciuric stone-forming conditions.