P2RX7 gene variants associate with altered inflammasome assembly and reduced pyroptosis in chronic nonbacterial osteomyelitis (CNO).

Chronic nonbacterial osteomyelitis (CNO), an autoinflammatory bone disease primarily affecting children, can cause pain, hyperostosis and fractures, affecting quality-of-life and psychomotor development. This study investigated CNO-associated variants in P2RX7, encoding for the ATP-dependent trans-membrane K+ channel P2X7, and their effects on NLRP3 inflammasome assembly. Whole exome sequencing in two related transgenerational CNO patients, and target sequencing of P2RX7 in a large CNO cohort (N = 190) were conducted. Results were compared with publicly available datasets and regional controls (N = 1873). Findings were integrated with demographic and clinical data. Patient-derived monocytes and genetically modified THP-1 cells were used to investigate potassium flux, inflammasome assembly, pyroptosis, and cytokine release. Rare presumably damaging P2RX7 variants were identified in two related CNO patients. Targeted P2RX7 sequencing identified 62 CNO patients with rare variants (32.4%), 11 of which (5.8%) carried presumably damaging variants (MAF <1%, SIFT "deleterious", Polyphen "probably damaging", CADD >20). This compared to 83 of 1873 controls (4.4%), 36 with rare and presumably damaging variants (1.9%). Across the CNO cohort, rare variants unique to one (Median: 42 versus 3.7) or more (≤11 patients) participants were over-represented when compared to 190 randomly selected controls. Patients with rare damaging variants more frequently experienced gastrointestinal symptoms and lymphadenopathy while having less spinal, joint and skin involvement (psoriasis). Monocyte-derived macrophages from patients, and genetically modified THP-1-derived macrophages reconstituted with CNO-associated P2RX7 variants exhibited altered potassium flux, inflammasome assembly, IL-1ß and IL-18 release, and pyroptosis. Damaging P2RX7 variants occur in a small subset of CNO patients, and rare P2RX7 variants may represent a CNO risk factor. Observations argue for inflammasome inhibition and/or cytokine blockade and may allow future patient stratification and individualized care.

New Insights into Adult and Paediatric Chronic Non-bacterial Osteomyelitis CNO.

PURPOSE OF REVIEW: To describe in detail the clinical synopsis and pathophysiology of chronic non-bacterial osteomyelitis and SAPHO syndrome. RECENT FINDINGS: Chronic non-bacterial osteomyelitis (CNO) has been identified as a disease entity for almost 50 years. This inflammatory bone disorder is characterized by osteolytic as well as hyperostotic/osteosclerotic lesions. It is chronic in nature, but it can present with episodic flairs and phases of remission, which have led to the denomination "chronic recurrent osteomyelitis", with its severe multifocal form "chronic recurrent multifocal osteomyelitis" (CRMO). For almost three decades, an infectious aetiology had been considered, since especially Propionibacterium acnes had been isolated from bone lesions of individual patients. However, this concept has been challenged since long-term antibiotic therapy did not alter the course of disease and modern microbiological techniques (including PCR) failed to confirm bone infection as an underlying cause. Over recent years, a profound dysregulation of cytokine expression profiles has been demonstrated in innate immune cells of CNO patients. A hallmark of monocytes from CNO patients is the failure to produce immune regulatory cytokines interleukin-10 (IL-10) and IL-19, which have been linked with genetic and epigenetic alterations. Subsequently, a significant upregulation of pro-inflammatory, NLRP3 inflammasome-dependent cytokines (IL-1ß and TNF-α), has been demonstrated. The current knowledge on CNO, the underlying molecular pathophysiology, and modern imaging strategies are summarized; differential diagnoses, treatment options, outcome measures, as well as quality of life studies are discussed.

Chronic Recurrent Multifocal Osteomyelitis (CRMO): Presentation, Pathogenesis, and Treatment.

PURPOSE OF REVIEW: Chronic non-bacterial osteomyelitis (CNO) with its most severe form chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory bone disorder. We summarize the clinical presentation, diagnostic approaches, most recent advances in understanding the pathophysiology, and available treatment options and outcomes in CNO/CRMO. RECENT FINDINGS: Though the exact molecular pathophysiology of CNO/CRMO remains somewhat elusive, it appears likely that variable defects in the TLR4/MAPK/inflammasome signaling cascade result in an imbalance between pro- and anti-inflammatory cytokine expressions in monocytes from CNO/CRMO patients. In this context, we present previously unpublished data on cytokine and chemokine expression in monocytes and tissues. CNO/CRMO is an autoinflammatory bone disorder resulting from imbalanced cytokine expression from innate immune cells. Though the exact molecular pathophysiology remains unclear, variable molecular defects appear to result in inflammasome activation and pro-inflammatory cytokine expression in monocytes from CNO/CRMO patients. Recent advances suggest signaling pathways and single molecules as biomarkers for CNO/CRMO as well as future treatment targets.

Chronic Nonbacterial Osteomyelitis: Pathophysiological Concepts and Current Treatment Strategies.

Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory bone disorder, covering a clinical spectrum with asymptomatic inflammation of single bones at the one end, and chronic recurrent multifocal osteomyelitis (CRMO) at the other end. The exact molecular pathophysiology of CNO remains largely unknown. Provided familial clusters and the association with inflammatory disorders of the skin and intestine suggest a genetic predisposition. Recently, profound dysregulation of cytokine responses was demonstrated in CRMO. Failure to produce antiinflammatory cytokines interleukin (IL)-10 and IL-19 contributes to activation of inflammasomes and subsequent IL-1ß release. In IL-10-deficient and in CNO-prone chronic multifocal osteomyelitis mice, IL-1ß was linked to bone inflammation. Further, alterations to the gut microbiome were suggested in contributing to IL-1ß release from innate immune cells in mice, offering an interesting target in the search for molecular mechanisms in CNO. Here, we summarize clinical presentation and treatment options in CNO/CRMO, current pathophysiological concepts, available mouse models, and promising future scientific directions.

Recombinant Enzyme Replacement Therapy in Hypophosphatasia.

Hypophosphatasia (HPP) is a rare monogenetic and multisystemic disease with involvement of different organs, including bone, muscle, kidney, lung, gastrointestinal tract and the nervous system. The exact metabolic mechanisms of the effects of TNAP deficiency in different tissues are not understood in detail. There is no approved specific treatment for HPP; therefore symptomatic treatment in order to improve the clinical features is of major interest. Enzyme replacement therapy (ERT) is a relatively new type of treatment based on the principle of administering a medical treatment replacing a defective or absent enzyme. Recently ERT with a bone targeted recombinant human TNAP molecule has been reported to be efficient in ten severely affected patients and improved survival of life threatening forms. These results are very promising especially with regard to the skeletal phenotype but it is unclear whether ERT also has beneficial effects for craniosynostosis and in other affected tissues in HPP such as brain and kidney. Long-term data are not yet available and further systematic clinical trials are needed. It is also necessary to establish therapeutic approaches to help patients who are affected by less severe forms of HPP but also suffer from a significant reduction in quality of life. Further basic research on TNAP function and role in different tissues and on its physiological substrates is critical to gain a better insight in the pathogenesis in HPP. This and further experiences in new therapeutic strategies may improve the prognosis and quality of life of patients with all forms of HPP.

Psychomotor development following early treatment of severe infantile vitamin B12 deficiency and West syndrome--is everything fine? A case report and review of literature.

BACKGROUND: Severe infantile vitamin B12 deficiency is occasionally reported in developed countries due to maternal nutritional deficiency. The clinical manifestation comprises megaloblastic anemia and neurodevelopmental delay culminating in demyelination and brain atrophy. Few case reports have documented manifestation of West syndrome. PATIENT: We report the 8-year long-term follow-up on a 6-month-old exclusively breast-fed girl with serious vitamin B12 deficiency secondary to undiagnosed maternal pernicious anemia. MRI revealed cerebral atrophy and delayed myelination. Strikingly, initial vitamin B12-mediated improvement of neurological and hematological findings was followed by temporary manifestation of infantile spasms requiring anticonvulsive therapy. RESULTS: Seizures soon dissolved, EEG and MRI scan normalized and developmental catch-up occurred. At the age of 8 years, the girl is symptom-free and visits primary school illustrating remarkable recovery of severe neurodevelopmental delay and symptomatic West syndrome. CONCLUSION: Infantile vitamin B12 deficiency has to be considered in the differential diagnosis of mental retardation and infantile spasms, especially if maternal nutritional deficiency might be suspected. Early treatment seems to be crucial for the prevention of irreversible brain damage.

Autoinflammatory bone disorders with special focus on chronic recurrent multifocal osteomyelitis (CRMO).

Sterile bone inflammation is the hallmark of autoinflammatory bone disorders, including chronic nonbacterial osteomyelitis (CNO) with its most severe form chronic recurrent multifocal osteomyelitis (CRMO). Autoinflammatory osteopathies are the result of a dysregulated innate immune system, resulting in immune cell infiltration of the bone and subsequent osteoclast differentiation and activation. Interestingly, autoinflammatory bone disorders are associated with inflammation of the skin and/or the intestine. In several monogenic autoinflammatory bone disorders mutations in disease-causing genes have been reported. However, regardless of recent developments, the molecular pathogenesis of CNO/CRMO remains unclear.Here, we discuss the clinical presentation and molecular pathophysiology of human autoinflammatory osteopathies and animal models with special focus on CNO/CRMO. Treatment options in monogenic autoinflammatory bone disorders and CRMO will be illustrated.

A clinical and pathomechanistic profile of chronic nonbacterial osteomyelitis/chronic recurrent multifocal osteomyelitis and challenges facing the field.

Sporadic chronic nonbacterial osteomyelitis (CNO) is the most common auto-inflammatory bone disorder. The clinical picture is highly variable ranging from nonsymptomatic monofocal lesions to chronic recurrent multifocal disease. Symptoms include pain, local swelling and warmth in the absence or presence of fever. A subset of CNO patients exhibits additional symptoms of psoriatic skin involvement, palmoplantar pustulosis and inflammatory bowel disease. Novel insights into the pathogenesis of CNO link the failure to produce IL-10 and the resulting imbalance toward pro-inflammatory IL-6 and TNF-α with disease expression. Treatment is empiric and includes NSAIDs, corticosteroids, sulfasalazine, methotrexate, TNF inhibitors and bisphosphonates. Laboratory studies and clinical trials are warranted to: establish biomarkers that predict flares and clinical outcomes, identify patients that require additional treatment on top of NSAIDs, establish evidence-based treatment regimens, allow a risk-benefit assessment for the available therapeutic strategies, and identify novel therapeutic targets.

Autoinflammatory bone disorders.

Autoinflammatory bone disorders are characterized by chronic non-infectious osteomyelitis and inflammation-induced bone resorption and result from aberrant activation of the innate immune system. Sporadic chronic non-bacterial osteomyelitis (CNO) is the most common disease subtype. The clinical picture is highly variable and the exact underlying pathophysiology remains to be determined. Recently, novel insights in the pathophysiology of sterile bone inflammation have been gathered by analyzing patients with rare, monogenic inflammatory diseases. In this overview CNO and Majeed syndrome, cherubism, hypophosphatasia and primary hypertrophic osteoarthropathy will be discussed. For the latter four disorders, a genetic cause affecting bone metabolism and leading to chronic bone inflammation has been described. The exact pathophysiology of CNO remains to be determined. Insights from monogenic autoinflammatory bone diseases and the identification of distinct inflammatory pathways may help to understand the pathogenesis of bone inflammation and inflammation-induced bone resorption in more common diseases.

Chronic non-bacterial osteomyelitis in childhood - a comprehensive review.

The clinical picture of childhood chronic recurrent multifocal osteomyelitis (CRMO) is characterized by an aseptic chronic osteomyelitis, most often affecting the metaphyses of the long bones. Skin inflammation (palmoplantar pustulosis, psoriatic lesions, acne) and inflammatory bowel disease may be associated with CRMO and therefore subsume this disease into the entity of SAPHO syndrome. Deregulated cytokine/chemokine expression in myeloid cells seems to drive chronic inflammation of the disease. NSAIDs may reduce pain, but additional second-line treatments (DMARDs, biologicals) are needed to treat persisting or progressing inflammation in a significant number of patients. The use of bisphosphonates may be a promising option in treating NSAID-refractory osteomyelitis in CRMO.

Attenuated TLR4/MAPK signaling in monocytes from patients with CRMO results in impaired IL-10 expression.

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory bone disorder of unknown origin. We previously demonstrated that monocytes from CRMO patients fail to express the immune-modulatory cytokine interleukin-10 (IL-10) in a chromatin dependent manner. Here, we demonstrate that attenuated extracellular-signal regulated kinase (ERK)1 and 2 signaling in response to TLR4 activation results in failure to induce IL-10 expression in monocytes from CRMO patients. Attenuated ERK1/2 activation results in 1) reduced levels of Sp-1, a transcription factor that induces IL-10 expression in monocytes, and 2) impaired H3S10 phosphorylation of the IL10 promoter, an activating epigenetic mark. The pro-inflammatory cytokines tumor necrosis factor (TNF)α and IL-6 are not negatively affected, resulting in an imbalance towards pro-inflammatory cytokines. Thus, impaired ERK1/2 signaling with subsequently reduced Sp-1 expression and H3S10 phosphorylation of the IL10 promoter may centrally contribute to the pathophysiology of CRMO.

Mutation screening of the IL-1 receptor antagonist gene in chronic non-bacterial osteomyelitis of childhood and adolescence.

OBJECTIVES: Chronic non-bacterial osteomyelitis CNO is an inflammatory disorder of the musculoskeletal system with unknown etiology. In addition to bone inflammation, patients may present with inflammatory involvement of other tissues including, e.g., skin. Recently, a novel syndrome due to deficiency of interleukin-1 receptor antagonist (IL1RN), DIRA has been identified. Clinically the syndrome is characterized by neonatal onset of pustular dermatosis, periostitis and chronic sterile multifocal osteomyelitis, strongly resembling CNO. Homozygous mutations of IL1RN have been identified and resulted in a truncated protein that is not secreted, hence leaving the action of interleukin-1 unopposed. METHODS: Because of similar clinical, radiological and histological features of CNO and DIRA, we hypothesized that both disorders might share a common autoinflammatory process. Thus, we searched for the presence of mutations in the interleukin-1 receptor antagonist gene in 60 patients diagnosed with CNO. RESULTS: In one patient with chronic multifocal osteomyelitis a heterozygous missense variant: c.281G>T (p.Cys94Phe) was detected. In the other patients only frequent polymorphisms were found. CONCLUSIONS: Our findings were not able to confirm mutations in IL1RN being an important contributing factor to the pathogenesis of CNO.

Activated memory B cells may function as antigen-presenting cells in the joints of children with juvenile idiopathic arthritis.

OBJECTIVE: B cells impact the perpetuation of chronic inflammatory or autoimmune diseases in multiple ways. A role of B cells as antigen-presenting cells (APCs) in the pathogenesis of chronic arthritis in humans has been suggested; however, as of yet the presence of such B cells at the site of inflammation has not been demonstrated. This study was undertaken to investigate whether synovial B cells in patients with juvenile idiopathic arthritis (JIA) might display features of APCs. METHODS: The frequency, phenotype, and immunoglobulin repertoire of synovial B cells were studied by flow cytometry and single-cell polymerase chain reaction (PCR). Cytokine expression by B cells was analyzed by real-time PCR, and interaction between B cells and T cells was investigated in a mixed lymphocyte culture. RESULTS: CD27+IgD- and CD27-IgD- B cells accumulated in the joints of JIA patients and displayed an activated phenotype. Both B cell subsets expressed hypermutated and class-switched immunoglobulins, indicators of memory B cells. The accumulating memory B cells expressed the costimulatory molecules CD80/CD86 and showed a higher capacity to activate allogeneic T cells and prime a Th1 phenotype than their peripheral blood counterparts. CONCLUSION: Activated immunoglobulin class-switched CD27- and CD27+ memory B cells, indicating a phenotype of APCs with expression of costimulatory molecules, accumulate in the joints of patients with JIA and might be involved in the amplification of pathogenic T cell activation. These findings provide evidence that B cells play an antibody-independent immunopathologic role in human chronic inflammatory arthritis of childhood.

Varicella-zoster virus infections in immunocompromised patients - a single centre 6-years analysis.

BACKGROUND: Infection with varicella-zoster virus (VZV) contemporaneously with malignant disease or immunosuppression represents a particular challenge and requires individualized decisions and treatment. Although the increasing use of varicella-vaccines in the general population and rapid initiation of VZV-immunoglobulins and acyclovir in case of exposure has been beneficial for some patients, immunocompromised individuals are still at risk for unfavourable courses. METHODS: In this single center, 6-year analysis we review incidence, hospitalization and complication rates of VZV-infections in our center and compare them to published data. Furthermore, we report three instructive cases. RESULTS: Hospitalization rate of referred children with VZV-infections was 45%, among these 17% with malignancies and 9% under immunosuppressive therapy. Rate of complications was not elevated in these two high-risk cohorts, but one ALL-patient died due to VZV-related complications. We report one 4-year old boy with initial diagnosis of acute lymphoblastic leukemia who showed a rapidly fatal outcome of his simultaneous varicella-infection, one 1.8-year old boy with an identical situation but a mild course of his disease, and an 8.5-year old boy with a steroid-dependent nephrotic syndrome. This boy developed severe hepatic involvement during his varicella-infection but responded to immediate withdrawl of steroids and administration of acyclovir plus single-dose cidofovir after nonresponse to acyclovir after 48 h. CONCLUSION: Our data show that patients with malignant diseases or immunosuppressive therapy should be hospitalized and treated immediately with antiviral agents. Despite these measures the course of VZV-infections can be highly variable in these patients. We discuss aids to individual decision-making for these difficult situations.

Gastroenteritis in childhood: a retrospective study of 650 hospitalized pediatric patients.

BACKGROUND: Acute diarrhea continues to be an important cause of hospitalization in young children, and deaths still occur as a result. We reviewed a large cohort of hospitalized children affected by gastroenteritis. The hypothesis of our study was that clinical characteristics and a limited set of laboratory data can differentiate between the different causative pathogens of diarrhea. METHODS: A chart review was performed of 650 patients with pathogen-proven diarrhea treated between April 2005 and May 2008 in the children's hospital of the University of Würzburg. Clinical presentation at the time of admission and during hospital stay, laboratory findings, stool pathogen results, and epidemiological data were collected and compared. A severity score was generated. RESULTS: Rotavirus was the most common gastroenteritis pathogen identified, followed by norovirus, adenovirus and Salmonella spp. Nosocomial infections were caused most commonly by norovirus. Rotavirus was the most common agent when there was simultaneous detection of two or more viruses. Rotavirus infections were significantly more severe, with a higher frequency of diarrhea and elevated liver enzymes. Infections due to Salmonella spp showed significantly higher values for C-reactive protein, erythrocyte sedimentation rate, and body temperature. A seasonal distribution was noted, with the peak for rotaviruses/noroviruses in winter/spring, the peak for adenoviruses in November/December, and the peak for Salmonella spp in the summer months. Younger children and toddlers had significantly higher gastroenteritis and airway inflammation scores. Of note, respiratory symptoms and parameters of systemic inflammation differed between the different pathogens. CONCLUSIONS: Gastroenteritis is a common reason for hospital admission in previously healthy children during the first years of life. Rotaviruses were found to be the most common pathogens in our cohort. On the basis of clinical and laboratory parameters it appears possible to distinguish between the different causative agents. This may have implications for hospital hygiene management and for the identification of predictive markers of a severe course.

Corticosteroid-induced spinal epidural lipomatosis in the pediatric age group: report of a new case and updated analysis of the literature.

Spinal epidural lipomatosis is a rare complication of chronic corticosteroid treatment. We report a new pediatric case and an analysis of this and 19 pediatric cases identified in the international literature. The youngest of these combined 20 patients was 5 years old when lipomatosis was diagnosed. Lipomatosis manifested after a mean of 1.3 (+/- 1.5) years (SD) (median, 0.8 years; range, 3 weeks - 6.5 years) of corticosteroid treatment. The corticosteroid dose at the time of presentation of the lipomatosis ranged widely, between 5 and 80 mg of prednisone/day. Back pain was the most common presenting symptom. Imaging revealed that lipomatosis almost always involved the thoracic spine, extending into the lumbosacral region in a subset of patients. Predominantly lumbosacral involvement was documented in only two cases. Although a neurological deficit at presentation was documented in about half of the cases, surgical decompression was not performed in the cases reported after 1996. Instead, reducing the corticosteroid dose (sometimes combined with dietary restriction to mobilize fat) sufficed to induce remission. In summary, pediatric spinal epidural lipomatosis remains a potentially serious untoward effect of corticosteroid treatment, which, if recognized in a timely manner, can have a good outcome with conservative treatment.