Explainable deep learning for disease activity prediction in chronic inflammatory joint diseases.

Analysing complex diseases such as chronic inflammatory joint diseases (CIJDs), where many factors influence the disease evolution over time, is a challenging task. CIJDs are rheumatic diseases that cause the immune system to attack healthy organs, mainly the joints. Different environmental, genetic and demographic factors affect disease development and progression. The Swiss Clinical Quality Management in Rheumatic Diseases (SCQM) Foundation maintains a national database of CIJDs documenting the disease management over time for 19'267 patients. We propose the Disease Activity Score Network (DAS-Net), an explainable multi-task learning model trained on patients' data with different arthritis subtypes, transforming longitudinal patient journeys into comparable representations and predicting multiple disease activity scores. First, we built a modular model composed of feed-forward neural networks, long short-term memory networks and attention layers to process the heterogeneous patient histories and predict future disease activity. Second, we investigated the utility of the model's computed patient representations (latent embeddings) to identify patients with similar disease progression. Third, we enhanced the explainability of our model by analysing the impact of different patient characteristics on disease progression and contrasted our model outcomes with medical expert knowledge. To this end, we explored multiple feature attribution methods including SHAP, attention attribution and feature weighting using case-based similarity. Our model outperforms temporal and non-temporal neural network, tree-based, and naive static baselines in predicting future disease activity scores. To identify similar patients, a k-nearest neighbours regression algorithm applied to the model's computed latent representations outperforms baseline strategies that use raw input features representation.

Concomitant Sjögren's disease as a biomarker for treatment effectiveness in rheumatoid arthritis - results from the Swiss clinical quality management cohort.

OBJECTIVE: To investigate the clinical phenotype and treatment response in patients with rheumatoid arthritis (RA) with and without concomitant Sjögren's disease (SjD). METHODS: In this observational cohort study, patients with RA from the Swiss Clinical Quality Management in Rheumatic Diseases registry were categorised according to the presence or absence of SjD. To assess treatment effectiveness, drug retention of tumor necrosis factor-α-inhibitors (TNFi) was compared to other mode of action (OMA) biologics and Janus kinase-inhibitors (JAKi) in RA patients with and without SjD. Adjusted hazard ratios (HR) for time to drug discontinuation were compared in crude and adjusted Cox proportional regression models for potential confounders. RESULTS: We identified 5974 patients without and 337 patients with concomitant SjD. Patients with SjD were more likely to be female, to have a positive rheumatoid factor, higher disease activity scores, and erosive bone damage. For treatment response, a total of 6781 treatment courses were analysed. After one year, patients with concomitant SjD were less likely to reach DAS28 remission with all three treatment modalities. Patients with concomitant SjD had a higher hazard for stopping TNFi treatment (adjusted HR 1.3 [95% CI 1.07-1.6]; OMA HR 1.12 [0.91-1.37]; JAKi HR 0.97 [0.62-1.53]). When compared to TNFi, patients with concomitant SjD had a significantly lower hazard for stopping treatment with OMA (adjusted HR 0.62 [95% CI 0.46-0.84]) and JAKi (HR 0.52 [0.28-0.96]). CONCLUSION: RA patients with concomitant SjD reveal a severe RA phenotype, are less responsive to treatment, and more likely to fail TNFi.

[Immunoglobulin A vasculitis]. / Immunglobulin-A-Vaskulitis.

The immune-mediated small vessel vasculitis is known as Schoenlein-Henoch purpura predominantly from pediatrics and in these cases occurs more frequently after infections of the upper airways. In adults, immunoglobulin A (IgA) vasculitis often proceeds more severely und recurrently with the classical tetrad of skin manifestations in the sense of leukocytoclastic vasculitis, joint affection, gastrointestinal involvement and IgA nephritis, in contrast to the mostly mild and self-limiting course in children. The background of this systemic vasculitis with formation of IgA immune complexes is considered to be an altered glycosylation of IgA, as this causes the exposure of binding sites for autoantibodies so that an immune complex reaction can be elicited. This ultimately leads to perivascular deposition of IgA and a further activation of neutrophils. Groundbreaking in the diagnostics is the histological detection of leukocytoclastic vasculitis and in cases of renal manifestations a kidney biopsy with characteristic deposits of immune complexes, which cannot be clearly differentiated from IgA nephropathy. The treatment is aimed at the respective manifestation and is mostly based on consensus recommendations due to the lack of randomized studies. In addition to immunosuppressive medication, in the presence of a chronic kidney disease general nephroprotection is becoming increasingly more important also by inhibition of sodium-glucose transporter 2 (SGLT2). The type and extent of kidney involvement and also rare cardiac manifestations are the main determinants of the prognosis. Continuous medical accompaniment of those affected is necessary due to the possible progression of the disease and the risk of recurrence.

Low-dose radiotherapy for greater trochanteric pain syndrome-a single-centre analysis.

PURPOSE: To determine predictive factors associated with a good response (GR) to and efficacy of low-dose radiotherapy (LDRT) in patients with greater trochanteric pain syndrome (GTPS). METHODS: Patients with GTPS were irradiated on a linear accelerator with 0.5-1.0 Gy per fraction to a total dose of 3.0-4.0 Gy per series. The endpoint was subjective good response (GR) to treatment 2 months after completion of the last LDRT series, defined as complete pain relief or marked improvement assessed using the von Pannewitz score. A positive response to steroid injection (SI) was defined as pain relief of at least 7 days. Patient and treatment-related characteristics were evaluated with respect to LDRT outcomes. RESULTS: Outcomes were assessed for 71 peritrochanteric spaces (PTSs; 65 patients, 48 females, with mean age of 63 [44-91] years). Prior SI had been given to 55 (77%) PTSs and 40 PTSs received two series of LDRT. Two months after completion of LDRT, GR was reported in 42 PTSs (59%). Two series of LDRT provided a significantly higher rate of GR than one series (72.5 vs. 42% PTSs, p = 0.015). Temporary pain relief after prior SI predicted GR to LDRT compared with PTSs which had not responded to SI (73 vs. 28% PTSs, p = 0.001). A regional structural abnormality, present in 34 PTSs (48%), was associated with a reduction of GR to LDRT (44 vs. 73% PTSs, p = 0.017). CONCLUSION: LDRT is an effective treatment for GTPS. Administration of two LDRT series, prior response to SI, and absence of structural abnormalities may predict significantly better treatment outcomes.

(p)ppGpp and moonlighting RNases influence the first step of lipopolysaccharide biosynthesis in Escherichia coli.

The outer membrane (OM) protects Gram-negative bacteria from harsh environmental conditions and provides intrinsic resistance to many antimicrobial compounds. The asymmetric OM is characterized by phospholipids in the inner leaflet and lipopolysaccharides (LPS) in the outer leaflet. Previous reports suggested an involvement of the signaling nucleotide ppGpp in cell envelope homeostasis in Escherichia coli. Here, we investigated the effect of ppGpp on OM biosynthesis. We found that ppGpp inhibits the activity of LpxA, the first enzyme of LPS biosynthesis, in a fluorometric in vitro assay. Moreover, overproduction of LpxA resulted in elongated cells and shedding of outer membrane vesicles (OMVs) with altered LPS content. These effects were markedly stronger in a ppGpp-deficient background. We further show that RnhB, an RNase H isoenzyme, binds ppGpp, interacts with LpxA, and modulates its activity. Overall, our study uncovered new regulatory players in the early steps of LPS biosynthesis, an essential process with many implications in the physiology and susceptibility to antibiotics of Gram-negative commensals and pathogens.

Management of giant-cell arteritis in Switzerland: an online national survey.

AIMS OF THE STUDY: To assess current practices in diagnosing, treating, and following-up giant-cell arteritis by specialists in Switzerland and to identify the main barriers to using diagnostic tools. METHODS: We performed a national survey of specialists potentially caring for patients with giant-cell arteritis. The survey was sent by email to all members of the Swiss Societies of Rheumatology and for Allergy and Immunology. A reminder was sent to nonresponders after 4 and 12 weeks. Its questions covered the following dimensions: respondents' main characteristics, diagnosis, treatment, and imaging's role during follow-up. The main study results were summarized using descriptive statistics. RESULTS: Ninety-one specialists, primarily aged 46-65 years (n = 53/89; 59%), working in academic or nonacademic hospitals or private practice, and treating a median of 7.5 (interquartile range [IQR]: 3-12) patients with giant-cell arteritis per year participated in this survey. Ultrasound of temporal arteries/large vessels (n = 75/90; 83%) and positron-emission-tomography-computed tomography (n = 52/91; 57%) or magnetic resonance imaging (n = 46/90; 51%) of the aorta/extracranial arteries were the most common techniques used to diagnose giant-cell arteritis with cranial or large vessel involvement, respectively. Most participants reported a short time to obtain imaging tests or arterial biopsy. The glucocorticoid tapering scheme, glucocorticoid-sparing agent, and glucocorticoid-sparing treatment duration varied among the participants. Most physicians did not follow a predefined repeat imaging scheme for follow-up and mainly relied on structural changes (vascular thickening, stenosis, or dilatation) to drive treatment choice. CONCLUSIONS: This survey indicates that imaging and temporal biopsy are rapidly accessible for diagnosing giant-cell arteritis in Switzerland but highlights heterogeneous practice in many disease management areas.

The Joint Vasculitis Registry in German-speaking countries (GeVas) - a prospective, multicenter registry for the follow-up of long-term outcomes in vasculitis.

BACKGROUND: Vasculitides comprise a group of rare diseases which affect less than 5 in 10.000 individuals. Most types of vasculitis can become organ- and life-threatening and are characterized by chronicity, high morbidity and relapses, altogether resulting in significant morbidity and mortality. Previous studies have been either monocentric or mainly retrospective - studies with a prospective design mostly consisted of rather small cohorts of 100 to 200 patients. The aim of the Joint Vasculitis Registry in German-speaking countries (GeVas) is to record all patients who have been recently diagnosed with vasculitis or who have changed their treatment due to a relapse (inception cohort). In GeVas, data are collected prospectively in a multicenter design in Germany, Austria and Switzerland. By this approach, courses of vasculitis and their outcomes can be monitored over an extended period. METHODS: GeVas is a prospective, web-based, multicenter, clinician-driven registry for the documentation of organ manifestations, damage, long-term progress and other outcomes of various types of vasculitis. The registry started recruiting in June 2019. As of October 2020, 14 centers have been initiated and started recruiting patients in Germany. Involvement of sites in Austria and the German-speaking counties of Switzerland is scheduled in the near future. DISCUSSION: In June 2019, we successfully established a prospective multicenter vasculitis registry being the first of its kind in German-speaking countries. The participating centers are currently recruiting, and systematic analysis of long-term vasculitis outcomes is expected in the ensuing period. TRIAL REGISTRATION: German Clinical Trials Register (Deutsches Register Klinischer Studien): DRKS00011866 . Registered 10 May 2019.

Clinically established biodegradable long acting injectables: An industry perspective.

Long acting injectable formulations have been developed to sustain the action of drugs in the body over desired periods of time. These delivery platforms have been utilized for both systemic and local drug delivery applications. This review gives an overview of long acting injectable systems that are currently in clinical use. These products are categorized in three different groups: biodegradable polymeric systems, including microparticles and implants; micro and nanocrystal suspensions and oil-based formulations. Furthermore, the applications of these drug delivery platforms for the management of various chronic diseases are summarized. Finally, this review addresses industrial challenges regarding the development of long acting injectable formulations.

Behçet's syndrome: clinical presentation and prevalence in Switzerland.

OBJECTIVE: Behçet's syndrome is a rare systemic autoimmune/autoinflammatory disease affecting mucocutaneous tissues, the skin and the eyes, as well as the joints, the central nervous system, the gastrointestinal tract and blood vessels. Because of the lack of clinical data in Switzerland, the aims of this cohort study were to calculate the disease prevalence and to analyse the disease manifestations and the immune-suppressive medication. METHODS: Data were extracted from 52 patient charts. Thereafter, all patients were interviewed with a questionnaire and 46 had an additional physical examination and laboratory analyses. For calculation of prevalence, data of the national statistical bureau were used. RESULTS: A disease prevalence of 4.03/100,000 inhabitants was calculated. The mean delay between first disease manifestation and diagnosis was 8 years. It was 2 years longer for Swiss than for non-Swiss individuals (p = 0.45). The time intervals between diagnosis and occurrence of different organ manifestations ranged from +8 to -11 years. There was no difference in organ involvement between different ethnicities. Colchicine was prescribed for 52% of patients only, whereas tumour necrosis factor (TNF) inhibitors and glucocorticoids were most frequently prescribed (80 and 64%, respectively). In almost half of the patients, TNF blockers could be stopped and replaced by conventional immunosuppressive drugs. CONCLUSION: The data from this cohort of Behçet's syndrome patients, the largest in Switzerland, documents a prevalence higher than anticipated. The diagnostic delay underlines an urgent need to improve awareness of the disease and allow timely treatment.

Peripheral and central nervous system involvement in a patient with primary Sjögren's syndrome: a case report.

BACKGROUND: Primary Sjögren's syndrome is the second most common rheumatological disorder after rheumatoid arthritis. It typically presents as xerophthalmia and xerostomia in postmenopausal women. Involvement of the central nervous system has been recognized, although its pathogenesis and characteristics are poorly understood. Central nervous system complications are a diagnostic challenge and emphasize the need for systematic screening of patients with new peripheral and central neurological symptoms. CASE REPORT: We report a case of a 58-year-old Swiss woman presenting with rapidly progressive sensorimotor distal polyneuropathy together with new-onset generalized seizures. Initial magnetic resonance imaging (MRI) of the brain performed after the first seizure showed multiple, bihemispheric, confluent white matter hyperintensities with contrast enhancement. Follow-up imaging 3 days after the initial magnetic resonance imaging demonstrated a fulminant disease progression associated with the serious clinical deterioration of the patient. In light of the results of a minor salivary gland biopsy, autoantibody testing, nerve conduction studies, and cranial magnetic resonance imaging, primary Sjögren's syndrome with cryoglobulinemia type II was diagnosed. Response to plasmapheresis and subsequent administration of cyclophosphamide was favorable. CONCLUSION: Even though exocrinopathy is the hallmark of Sjögren's syndrome, systemic symptoms are observed in one-third of patients. There is an urgent need to better characterize the mechanisms underlying different disease phenotypes and to perform randomized controlled trials in order to provide tailored and evidence-based treatment for primary Sjögren's syndrome.

Risk of relapse after discontinuation of tocilizumab therapy in giant cell arteritis.

OBJECTIVE: It is currently unknown how long GCA should be treated with tocilizumab. In the first randomized controlled trial, the biologic agent was stopped after 52 weeks. We therefore studied what proportion of patients relapsed, when relapses occurred and whether factors might predict relapse after tocilizumab treatment discontinuation. METHODS: All patients in the tocilizumab arm who had received a 52-week treatment were evaluated. In case of lasting remission, magnetic resonance angiography (MRA) was performed and sera were taken to search for biomarkers associated with subclinical disease activity. RESULTS: Seventeen of 20 patients randomized to the tocilizumab treatment arm were in lasting remission without any co-medication at week 52. Mean follow-up after study end was 28.1 months (range 17-44). Eight patients relapsed after a mean of 6.3 months (range 2-14) (six within the first 5 months, two patients at months 13 and 14, respectively). Relapsing patients were younger and showed more signs of mural enhancement in MRA compared with non-relapsing patients. MRA documented low-intensity vessel wall signals in all subjects. No morphological changes such as formation of aneurysm of aorta occurred. Biomarkers in sera did not indicate subclinical disease activity: levels of IL-6, MMP-3, soluble TNF receptor 2, soluble CD163, soluble intercellular adhesion molecule-1 and Pentraxin-3 did not differ from matched healthy controls. CONCLUSION: The data show that a 52-week treatment with tocilizumab induces a lasting remission that persists in half of the patients after treatment stop. None of the clinical, serological or MRA findings qualify to predict relapse. Remarkably, MRA revealed a persisting wall enhancement of the descending aorta.

Safety and immunogenicity of tetanus/diphtheria vaccination in patients with rheumatic diseases-a prospective multi-centre cohort study.

OBJECTIVES: We aimed to assess the safety and immunogenicity of a diphtheria/tetanus vaccine booster dose in three different patient groups with rheumatic diseases on a variety of immunosuppressive/immunomodulatory medications compared with healthy controls (HCs). METHODS: We conducted a multi-centre prospective cohort study in Switzerland. We enrolled patients with RA, axial SpA/PsA, vasculitis (Behçet's disease, ANCA-associated vasculitis) and HCs. Diphtheria/tetanus vaccination was administered according to the Swiss vaccination recommendations. Blood samples were drawn before vaccination, and 1 month and 3 months afterwards. Antibody concentrations against vaccine antigens were measured by ELISA. Immunogenicity was compared between patient and medication groups. A mixed model was applied for multivariate analysis. Missing data were dealt with using multiple imputation. RESULTS: Between January 2014 and December 2015, we enrolled 284 patients with rheumatic diseases (131 RA, 114 SpA/PsA, 39 vasculitis) and 253 HCs. Of the patients, 89% were on immunosuppressive/immunomodulatory medication. Three months post-vaccination 100% of HCs vs 98% of patients were protected against tetanus and 84% vs 73% against diphtheria. HCs and SpA/PsA patients had significantly higher responses than RA and vasculitis patients. Assessing underlying diseases and medications in a multivariate model, rituximab was the only factor negatively influencing tetanus immunogenicity, whereas only MTX treatment had a negative influence on diphtheria antibody responses. No vaccine-related serious adverse events were recorded. CONCLUSION: Diphtheria/tetanus booster vaccination was safe. Tetanus vaccination was immunogenic; the diphtheria component was less immunogenic. Vaccine responses were blunted by rituximab and MTX. TRIAL REGISTRATION: ClinicalTrials.gov, http://clinicaltrials.gov, Identifier: NCT01947465.

GPCR-specific autoantibody signatures are associated with physiological and pathological immune homeostasis.

Autoantibodies have been associated with autoimmune diseases. However, studies have identified autoantibodies in healthy donors (HD) who do not develop autoimmune disorders. Here we provide evidence of a network of immunoglobulin G (IgG) autoantibodies targeting G protein-coupled receptors (GPCR) in HD compared to patients with systemic sclerosis, Alzheimer's disease, and ovarian cancer. Sex, age and pathological conditions affect autoantibody correlation and hierarchical clustering signatures, yet many of the correlations are shared across all groups, indicating alterations to homeostasis. Furthermore, we identify relationships between autoantibodies targeting structurally and functionally related molecules, such as vascular, neuronal or chemokine receptors. Finally, autoantibodies targeting the endothelin receptor type A (EDNRA) exhibit chemotactic activity, as demonstrated by neutrophil migration toward HD-IgG in an EDNRA-dependent manner and in the direction of IgG from EDNRA-immunized mice. Our data characterizing the in vivo signatures of anti-GPCR autoantibodies thus suggest that they are a physiological part of the immune system.

[Adolescent rheumatism : The same but different]. / Rheuma beim Jugendlichen : Das Gleiche ist nicht dasselbe.

Between childhood and adulthood, there often exists a difficult period of coming of age. This phase frequently represents a significant challenge for adolescents and young adults at the physical, psychological, and social level. Having trouble with adolescence itself it puts an extra weight on young people with chronic rheumatic diseases. Thus, medical and interpersonal support can be multifaceted. In light of this, support from an interprofessional team in the form of a specialist transition clinic has proven to be of great value. In the outpatient clinic established at the Inselspital Bern (Bern University Hospital), specialists in pediatric and adult rheumatology work together with a team of nurses, physiotherapists, occupational therapists, social workers, and psychologists, who are called in on an individual-requirement basis. All personnel involved in the care of these young patients should understand that a rheumatic disease developing in childhood normally progresses differently than it does if first developed during adulthood.

Immuno-monitoring reveals an extended subclinical disease activity in tocilizumab-treated giant cell arteritis.

Objective: Tocilizumab is effective in inducing and maintaining remission of GCA. Despite clinical and serological control of disease, magnetic resonance angiography may show persistence of inflammatory signals of unknown significance in arterial walls. Thus, there is an unmet need for tools to detect subclinical disease activity. Methods: Immune-inflammatory markers were measured in prospectively collected sera of the first randomized, double-blind, placebo-controlled trial investigating the use of tocilizumab in GCA. As a comparison, immune-inflammatory markers were also measured in sera from age- and sex-matched healthy volunteers. The biomarkers were quantified using luminex technology. Results: Of all the parameters determined, only MMP-3, pentraxin-3 and sTNFR2 were significantly elevated, while ICAM-1 and CD163 were significantly decreased during the early stages of the study, at time points of full clinical remission under treatment with tocilizumab plus glucocorticoids. In contrast, tocilizumab monotherapy towards the end of the study resulted in an almost complete normalization of immune-inflammatory molecules, as defined by the healthy controls. MMP-3 levels showed a weak association with magnetic resonance signal intensity; none of the biomarkers predicted relapse occurring within 6 months after study end. Conclusion: The data documented a subclinical disease activity in GCA that was more pronounced during the early stages of treatment and almost disappeared towards the study end. They indicated that tocilizumab treatment of at least 52 weeks is necessary in order to reset a broad range of immune-inflammatory pathways. Trial registration: ClinicalTrials.gov, http://clinicaltrials.gov, NCT01450137.

Magnetic resonance angiography in giant cell arteritis: results of a randomized controlled trial of tocilizumab in giant cell arteritis.

Objective: To analyse magnetic resonance angiographic (MRA) vessel wall signals from a randomized controlled trial of tocilizumab (TCZ) to treat GCA. Methods: Participants were assigned in a 2:1 ratio to receive either TCZ + glucocorticoids (GCs) or placebo + GC infusions at 4-week intervals for 52 weeks. GCs were started at 1 mg/kg/day, then tapered to 0.1 mg/kg/day at week 12 and thereafter down to zero. Patients with initial positive MRA findings underwent control MRA at weeks 12 and 52. Vessel wall signals were scored from 0 (normal) to 3 (intense late enhancement). Outcomes were the number of patients with complete MRA remission at weeks 12 and 52, and changes in vasculitis score, vessel anatomy and atherosclerosis. Results: Of the 30 randomized participants, nine TCZ and two placebo patients had no vessel wall enhancement on initial MRA. At week 12, MRAs were performed in nine TCZ and four placebo patients (nine and three in clinical remission, respectively). Three (33%) TCZ patients showed normalization of vessel wall signals compared with one (25%) placebo patient. At week 52, there was additional MRA improvement in some TCZ patients, but one-third showed persistent or increased late vessel wall enhancement. There was no formation of aneurysms or stenosis and no increase in atherosclerosis. Conclusions: Although TCZ resulted in complete clinical and laboratory remission of GCA over 52 weeks, MRA signals in vessel walls normalized in only one-third of patients. Whether these signals are of prognostic importance remains to be determined.

Systemic sclerosis associated interstitial lung disease - individualized immunosuppressive therapy and course of lung function: results of the EUSTAR group.

BACKGROUND: Interstitial lung disease in systemic sclerosis (SSc-ILD) is a major cause of SSc-related death. Imunosuppressive treatment (IS) is used in patients with SSc for various organ manifestations mainly to ameliorate progression of SSc-ILD. Data on everyday IS prescription patterns and clinical courses of lung function during and after therapy are scarce. METHODS: We analysed patients fulfilling American College of Rheumatology (ACR)/European League against Rheumatism (EULAR) 2013 criteria for SSc-ILD and at least one report of IS. Types of IS, pulmonary function tests (PFT) and PFT courses during IS treatment were evaluated. RESULTS: EUSTAR contains 3778/11,496 patients with SSc-ILD (33%), with IS in 2681/3,778 (71%). Glucocorticoid (GC) monotherapy was prescribed in 30.6% patients with GC combinations plus cyclophosphamide (CYC) (11.9%), azathioprine (AZA) (9.2%), methotrexate (MTX) (8.7%), or mycophenolate mofetil (MMF) (7.3%). Intensive IS (MMF + GC, CYC or CYC + GC) was started in patients with the worst PFTs and ground glass opacifications on imaging. Patients without IS showed slightly less worsening in forced vital capacity (FVC) when starting with FVC 50-75% or >75%. GC showed negative trends when starting with FVC <50%. Regarding diffusing capacity for carbon monoxide (DLCO), negative DLCO trends were found in patients with MMF. CONCLUSIONS: IS is broadly prescribed in SSc-ILD. Clusters of clinical and functional characteristics guide individualised treatment. Data favour distinguished decision-making, pointing to either watchful waiting and close monitoring in the early stages or start of immunosuppressive treatment in moderately impaired lung function. Advantages of specific IS are difficult to depict due to confounding by indication. Data do not support liberal use of GC in SSc-ILD.

Identification of a MAFB mutation in a patient with multicentric carpotarsal osteolysis.

Multicentric carpotarsal osteolysis (MCTO) is an autosomal dominant disease of the skeleton characterised by progressive destruction of carpal and tarsal bones. Recently, it has been demonstrated that this disease is caused by heterozygous mutations in the gene for the transcriptional repressor MAFB. We analysed genomic DNA and RNA from leucocytes of a female patient diagnosed with MCTO. We identified the mutation c.161C>T in the genomic sequence and in the expressed messenger RNA for MAFB. This is the second report of the c.161C>T mutation in a MCTO patient. Since the parents do not possess this mutation, the daughter must have acquired a de novo mutation. At the level of the gene, this mutation is found at a CpG dinucleotide sequence, suggesting that DNA methylation was involved in the occurrence of the DNA aberration. At the level of the protein, the mutation exchanges a serine with a leucine residue at a position on MAFB that can become phosphorylated in the wild-type protein. MAFB negatively regulates the RANKL-dependent differentiation of monocytes into osteoclasts. It is likely that the mutation will affect the phosphorylation status of the protein and its biological activity. When the activity of the transcriptional repressor is reduced, osteoclastogenesis will be increased, which might explain the carpotarsal bone destruction observed in the patient.