Autosomal dominant granulomatous arthritis, uveitis, skin rash, and synovial cysts

Distinct NOD2 mutations reported in three families with Blau syndrome (BS) from a single center in India - Case series and review of literature

OBJECTIVE

Blau syndrome (BS), considered a rare pediatric autoinflammatory disease, is characterised by a triad of granulomatous arthritis, dermatitis and uveitis. Here we present a tale of three families visited in our outpatient department in the last two years (2020-2022) where more than one member was affected with either skin, ophthalmological and joint involvement with either biopsy-proven granuloma or genetic mutation at NOD2 gene suggesting the diagnosis of BS.

CASE SERIES

The first family had three affected members where the mother and her two children had skin changes, polyarthritis and a pathogenic mutation in NOD2 gene (exon 4, c.1000C > T, p.Arg334Trp) suggesting BS. The second family had two affected members where both mother and her son had uveitis, skin changes with NOD2 mutation at exon 4 with c.1147G > A (p Glu 383 Lys) variant. The son also had polyarthritis and his skin biopsy was suggestive of granulomatous inflammation. In the third family with two affected members, we found a mutation in NOD2 on exon 4 (c 1324C > T, p.Lys 442 Phe) which was described as pathogenic with only one report published till date.

CONCLUSION

These three cases presented to us within the last two years and led to a diagnosis of BS in three other family members with discrete mutations (commonest to rarest) on the NOD2 gene in the three families.

Potential Benefits of TNF Targeting Therapy in Blau Syndrome, a NOD2-Associated Systemic Autoinflammatory Granulomatosis

Blau syndrome is a systemic autoinflammatory granulomatous disease caused by mutations in the nucleotide-binding oligomerization domain 2 (NOD2) gene. NOD2 is an intracellular pathogen recognition receptor. Upon binding to muramyl dipeptide (MDP), NOD2 activates the NF-κB pathway, leading to the upregulation of proinflammatory cytokines. Clinical manifestations of Blau syndrome appear in patients before the age of four. Skin manifestations resolve spontaneously in some cases; however, joint and eye manifestations are progressive, and lead to serious complications, such as joint contracture and blindness. Currently, there is no specific curative treatment for the disease. Administration of high-dose oral steroids can improve clinical manifestations; however, treatments is difficult to maintain due to the severity of the side effects, especially in children. While several new therapies have been reported, including JAK inhibitors, anti-IL-6 and anti-IL-1 therapies, anti-TNF therapy plays a central role in the treatment of Blau syndrome. We recently performed an ex vivo study, using peripheral blood and induced pluripotent stem cells from patients. This study demonstrated that abnormal cytokine expression in macrophages from untreated patients requires IFNγ stimulation, and that anti-TNF treatment corrects the abnormalities associated with Blau syndrome, even in the presence of IFNγ. Therefore, although the molecular mechanisms by which the genetic mutations in NOD2 lead to granuloma formation remain unclear, it is possible that prior exposure to TNFα combined with IFNγ stimulation may provide the impetus for the clinical manifestations of Blau syndrome.

Blau syndrome: a rare cause of exuberant granulomatous synovitis of the knee

Blau syndrome (BS) is a rare autosomal dominant familial granulomatous inflammatory disease presenting in early childhood with dermatitis, arthritis and uveitis. Early-onset sarcoidosis represents the sporadic form, and both are characterised by mutations in the CARD15/NOD2 gene on chromosome 16. We describe a 38-year-old man with known BS who presented for orthopaedic review following right-sided patellar dislocation. MRI of the injured knee demonstrated diffuse synovitis and prominent fatty tissue resembling lipoma arborescens with evidence of recent patellar dislocation. Synovectomy was performed and confirmed granulomatous synovitis. Knee imaging findings are described for the first time. Combining distinct morphological bone changes with synovitis which resembles lipoma arborescens and histology which includes sarcoidal-type granulomatous synovitis should lead the radiologist and pathologist to consider the diagnosis of BS.

When to Suspect Autoinflammatory/Recurrent Fever Syndromes

Autoinflammatory disorders are disorders characterized by rash, arthritis, fever, and systemic inflammation. These disorders are caused by mutations in genes important in innate immune system sensors. This review highlights the workup of an individual with recurrent episodes of inflammation, features of these disorders, the genetic defects that cause these disorders, and the specific treatments available.

Caveats and truths in genetic, clinical, autoimmune and autoinflammatory issues in Blau syndrome and early onset sarcoidosis

Blau syndrome (BS) and early onset sarcoidosis (EOS) are, respectively, the familial and sporadic forms of the pediatric granulomatous autoinflammatory disease, which belong to the group of monogenic autoinflammatory syndromes. Both of these conditions are caused by mutations in the NOD2 gene, which encodes the cytosolic NOD2 protein, one of the pivotal molecules in the regulation of innate immunity, primarily expressed in the antigen-presenting cells. Clinical onset of BS and EOS is usually in the first years of life with noncaseating epithelioid granulomas mainly affecting joints, skin, and uveal tract, variably associated with heterogeneous systemic features. The dividing line between autoinflammatory and autoimmune mechanisms is probably not so clear-cut, and the relationship existing between BS or EOS and autoimmune phenomena remains unclear. There is no established therapy for the management of BS and EOS, and the main treatment aim is to prevent ocular manifestations entailing the risk of potential blindness and to avoid joint deformities. Nonsteroidal anti-inflammatory drugs, corticosteroids and immunosuppressive drugs, such as methotrexate or azathioprine, may be helpful; when patients are unresponsive to the combination of corticosteroids and immunosuppressant agents, the tumor necrosis factor-α inhibitor infliximab should be considered. Data on anti-interleukin-1 inhibition with anakinra and canakinumab is still limited and further corroboration is required. The aim of this paper is to describe BS and EOS, focusing on their genetic, clinical, and therapeutic issues, with the ultimate goal of increasing clinicians' awareness of both of these rare but serious disorders.

Granulomatous inflammation: The overlap of immune deficiency and inflammation

Pediatric granulomatous diseases constitute a heterogenous group of conditions in terms of clinical phenotypes, pathogenic mechanisms, and outcomes. The common link is the presence of multinucleated giant cells in the inflammatory infiltrate. The clinical scenario in which a tissue biopsy shows granulomatous inflammation is not an uncommon one for practicing adult and pediatric rheumatologists. Our role as rheumatologists is to develop a diagnostic plan based on a rational differential diagnostic exercise tailored to the individual patient and based mainly on a detailed clinical assessment. This chapter presents a comprehensive differential diagnosis associated with a classification developed by the authors. We describe with some detail extrapulmonary sarcoidosis, Blau syndrome, and immunodeficiency associated granulomatous inflammation, which in our view are the paradigmatic primary forms of granulomatous diseases in childhood. The other entities are presented only as differential diagnoses listing their most relevant clinical features. This chapter shows that almost all granulomatous diseases seen in adults can be found in children and that there are some entities that are essentially pediatric at onset, namely Blau syndrome and most forms of immunodeficiency associated granulomatous diseases.

Blau syndrome, the prototypic auto-inflammatory granulomatous disease

Blau syndrome is a monogenic disease resulting from mutations in the pattern recognition receptor NOD2, and is phenotypically characterized by the triad of granulomatous polyarthritis, dermatitis and uveitis. This paper reviews briefly the classical clinical features of the disease, as well as more recently described extra-triad symptoms. From an ongoing prospective multicenter study, we provide new data on the natural history of Blau syndrome, focusing on functional status and visual outcome. We also present an update of the range of different NOD2 mutations found in Blau syndrome as well as recent data on morphologic and immunohistochemical characteristics of the Blau granuloma. Finally, emerging insights into pathogenic mechanisms including activation of NOD2 signal transduction, and potential biomarkers of disease activity are discussed.

Early-onset sarcoidosis caused by a rare CARD15/NOD2 de novo mutation and responsive to infliximab: a case report with long-term follow-up and review of the literature

Granulomatous autoinflammatory diseases are monogenic syndromes caused by mutations in the region encoding for the nucleotide-binding domain region of the NOD2/CARD15 gene with subsequent dysregulation of the inflammatory response and formation of noncaseous granulomas. They include Blau syndrome (BS) and early-onset sarcoidosis (EOS); both are clinically and genetically indistinguishable between them and they are the familial (autosomal dominantly inherited) and sporadic forms of the same disease, respectively. We describe a case of EOS, misdiagnosed for 30 years such as "juvenile rheumatoid arthritis" before and "classic sarcoidosis" later. In our patient, we found a new de novo mutation (E383G) in NOD2 that has been reported only in a family of Japanese patients with BS. After long-term follow-up (42 months), infliximab maintained good efficacy and safety without any sign of disease relapse and side effects.

Autoinflammation: From monogenic syndromes to common skin diseases

Autoinflammation is characterized by aberrant regulation of the innate immune system and often manifests as periodic fevers and systemic inflammation involving multiple organs, including the skin. Mutations leading to abnormal behavior or activity of the interleukin 1 beta (IL-1ß)-processing inflammasome complex have been found in several rare autoinflammatory syndromes, for which anticytokine therapy such as IL-1 or tumor necrosis factor-alfa inhibition may be effective. It is becoming clear that features of autoinflammation also affect common dermatoses, some of which were previously thought to be solely autoimmune in origin (eg, vitiligo, systemic lupus erythematosus). Recognizing the pathogenetic role of autoinflammation can open up new avenues for the targeted treatment of complex, inflammatory dermatoses.

Monogenic causes of inflammatory disease in rheumatology

PURPOSE OF REVIEW

To review the single-gene defects that can mimic rheumatologic diseases.

RECENT FINDINGS

Monogenic disorders can cause a variety of diseases that may be seen by a rheumatologist. Many of these illnesses present with recurrent episodes of arthritis, rash, fever and inflammation, and serositis. Recent discoveries have defined inflammatory diseases due to mutations in the IL-1 and IL-36 receptor antagonists, as well as the immunoproteosome. Further study of well defined monogenic causes of inflammatory diseases, such as FMF, PAPA, TRAPS, and HIDS, has elucidated the pathophysiology of these diseases leading to targeted immunotherapy with anticytokine biological medications.

SUMMARY

A rheumatologist should be aware of the genetic causes of inflammatory disease mimics. This will not only help with the prognosis of these diseases, but also help to guide therapy to prevent long-term complications associated with these disorders.

Blau syndrome, clinical and genetic aspects

Blau syndrome (BS) is a rare autosomal dominant, autoinflammatory syndrome characterized by the clinical triad of granulomatous recurrent uveitis, dermatitis and symmetric arthritis. The gene responsible for BS has been identified in the caspase recruitment domain gene CARD15/NOD2. In the majority of patients, the disease is characterized by early onset, usually before 3-4years of age. The manifestations at disease onset are usually represented by articular and cutaneous involvement signs, generally followed later by ocular manifestations which are often the most relevant morbidity of BS. In some cases the presence of fever is also observed; atypical cases of BS have been reported with cardiovascular, neurological, renal, intestinal and other organ involvement. The rarity and the variations in the severity and evolution of its expressions do not permit sufficient data about optimal treatment for patients with BS. The first step of therapy is represented by the use of corticosteroids and successively, in case of unsatisfactory response, by additional treatment with immunosuppressive agents. The results with biologic anti-cytokine agents, such as anti-TNFα and anti-IL1β, are different, particularly with regard to ocular morbidity. Clinical and genetic aspects of the familial and the sporadic form of BS will be discussed and focused on. A description of a case study of an Italian family is also included.

Miscellaneous non-inflammatory musculoskeletal conditions. Blau syndrome

Blau syndrome (BS) is a rare dominantly inherited, inflammatory syndrome characterised by the clinical triad of granulomatous dermatitis, symmetric arthritis and recurrent uveitis. The caspase recruitment domain gene CARD15/NOD2 has been identified as the gene responsible for BS. In the majority of patients, the disease is characterised by early onset, usually before 3-4 years of age. Onset is most often articular and cutaneous. Eye symptoms usually start later; however, eye involvement is the most relevant morbidity of BS. Atypical cases of BS have been reported with involvement of organs other than skin, joint and eyes. Due to its rarity and the variations in the severity and evolution of its expressions, there have been no studies on the optimal treatment for patients with BS. If the therapeutic response to corticosteroids is unsatisfactory, additional treatment with immunosuppressive agents should be tried. The results with biologic anti-cytokine agents, such as infliximab and anakinra, are variable, particularly with regard to ocular morbidity. This review will focus on the clinical and genetics aspects of the familial and the sporadic form of BS. Further, we will describe an Italian family followed by us over the past 25 years.

Co-existence of chronic renal failure, renal clear cell carcinoma, and Blau syndrome

Blau syndrome is a rare, multisystem, autosomal-dominant, and granulomatous disorder caused by susceptibility variants in the NOD2 gene. We describe here a 14-year-old girl with Blau syndrome with incidentally diagnosed renal carcinoma. The index case presented with growth retardation and recurrent symmetric arthritis. Her clinical symptoms included bilateral cataract due to recurrent uveitis, camptodactyly, and persistent erythematous rash with ichthyosis. Her two sisters and her mother were affected with combinations of these conditions-symmetric polyarthritis, uveitis, and skin involvement-suggesting an autosomal dominant trait. The index case developed a chronic renal insufficiency, and an abdominal computerized tomography scan revealed a 2.5-cm mass in the left kidney. The histopathological examination showed renal clear cell carcinoma, chronic tubulointerstitial nephritis,and giant cell granulomas in both the tumor and nonneoplastic renal tissue. Granulomatous inflammation was observed in the skin biopsy specimen. The patient was diagnosed with Blau syndrome based on her family history, uveitis, granulomatous inflammation proved by skin biopsy, and polyarthritis. Sequencing of the NOD2 gene showed a heterozygous p.R334Q mutation in all affected family members. To the best of our knowledge, this is the first reported case of a patient with Blau syndrome accompanied by chronic renal failure and renal carcinoma.

Association of a de novo 16q copy number variant with a phenotype that overlaps with Lenz microphthalmia and Townes-Brocks syndromes

BACKGROUND

Anophthalmia and microphthalmia are etiologically and clinically heterogeneous. Lenz microphthalmia is a syndromic form that is typically inherited in an X-linked pattern, though the causative gene mutation is unknown. Townes-Brocks syndrome manifests thumb anomalies, imperforate anus, and ear anomalies. We present a 13-year-old boy with a syndromic microphthalmia phenotype and a clinical diagnosis of Lenz microphthalmia syndrome.

CASE PRESENTATION

The patient was subjected to clinical and molecular evaluation, including array CGH analysis. The clinical features included left clinical anophthalmia, right microphthalmia, anteriorly placed anus with fistula, chordee, ventriculoseptal defect, patent ductus arteriosus, posteriorly rotated ears, hypotonia, growth retardation with delayed bone age, and mental retardation. The patient was found to have an approximately 5.6 Mb deletion of 16q11.2q12.1 by microarray based-comparative genomic hybridization, which includes the SALL1 gene, which causes Townes-Brocks syndrome.

CONCLUSIONS

Deletions of 16q11.2q12.2 have been reported in several individuals, although those prior reports did not note microphthalmia or anophthalmia. This region includes SALL1, which causes Townes-Brocks syndrome. In retrospect, this child has a number of features that can be explained by the SALL1 deletion, although it is not clear if the microphthalmia is a rare feature of Townes-Brocks syndrome or caused by other mechanisms. These data suggest that rare copy number changes may be a cause of syndromic microphthalmia allowing a personalized genomic medicine approach to the care of patients with these aberrations.

NOD2-associated pediatric granulomatous arthritis, an expanding phenotype: study of an international registry and a national cohort in Spain

OBJECTIVE

To study the phenotype characteristics of the largest to date cohort of patients with pediatric granulomatous arthritis (PGA) and documented mutations in the NOD2 gene.

METHODS

We analyzed merged data from 2 prospective cohorts of PGA patients, the International PGA Registry and a Spanish cohort. A systematic review of the medical records of interest was performed to identify phenotype characteristics.

RESULTS

Forty-five patients with PGA (23 sporadic cases and 22 from familial pedigrees) and documented NOD2 mutations were identified and formed the basis of the study. Of these 45 patients, 18 had the R334W-encoding mutation, 18 had R334Q, 4 had E383K, 3 had R587C, 1 had C495Y, and 1 had W490L. The majority of patients manifested the typical triad of dermatitis, uveitis, and arthritis. In contrast, in 13 patients, the following "atypical" manifestations were noted: fever, sialadenitis, lymphadenopathy, erythema nodosum, leukocytoclastic vasculitis, transient neuropathy, granulomatous glomerular and interstitial nephritis, interstitial lung disease, arterial hypertension, hypertrophic cardiomyopathy, pericarditis, pulmonary embolism, hepatic granulomatous infiltration, splenic involvement, and chronic renal failure. In addition, 4 individuals who were asymptomatic carriers of a disease-causing mutation were documented.

CONCLUSION

NOD2-associated PGA can be a multisystem disorder with significant visceral involvement. Treating physicians should be aware of the systemic nature of this condition, since some of these manifestations may entail long-term morbidity.

A novel mutation in the NOD2 gene associated with Blau syndrome: a Norwegian family with four affected members

BACKGROUND

Blau syndrome is a chronic granulomatous disease with an autosomal dominant trait characterized by the triad granulomatous dermatitis, arthritis, and uveitis. It is caused by mutations in the NOD2 gene, also termed the CARD15 gene.

OBJECTIVE

To report a novel mutation in the NOD2 gene associated with Blau syndrome.

METHODS AND RESULTS

The proband was a 68-year-old ethnic Norwegian male who had uveitis and arthritis since 10 years of age followed by lifelong recurrent arthritis and chronic eye involvement. Genetic analysis showed a heterozygous c.1814 C>A, T605N mutation in NOD2 that has not previously been described. All of his three children had Blau syndrome and had inherited the NOD2 mutation. The proband's first son had exanthema, arthritis, and uveitis from 10 years of age and later presented with granulomatous lymphadenopathy, granulomatous parotitis, and granulomatous intestinal inflammation. The proband's daughter had arthritis, uveitis, and exanthema from 3 years of age. The proband's second son had uveitis, exanthema, and arthritis from 1.5 years of age. None of the cases had any involvement of the heart or lungs.

CONCLUSION

We report a novel Blau syndrome-associated mutation with an autosomal dominant heritage. Most likely the mutation has arisen de novo in the proband. Genetic counselling and antenatal diagnostics should be available to the involved families.

Nucleotide oligomerization domain-2 (NOD2)-induced uveitis: dependence on IFN-gamma

PURPOSE

Nucleotide oligomerization domain-2 (NOD2) plays an important role in innate immunity to sense muramyl dipeptide (MDP), a component of bacterial cell walls. Notably, NOD2 is linked to eye inflammation because mutations in NOD2 cause a granulomatous type of uveitis called Blau syndrome. A mouse model of NOD2-dependent ocular inflammation was employed to test the role of a cytokine strongly implicated in granuloma formation, IFN-gamma, in order to gain insight into downstream functional consequences of NOD2 activation within the eye triggering uveitis.

METHODS

Mice deficient in IFN-gamma, NOD2, or CD11b and their wild-type controls were treated with intravitreal injection of MDP in the presence or absence of IFN-gamma. IFN-gamma production in the eye was measured by ELISA. The intravascular inflammatory response within the iris was quantified by intravital microscopy.

RESULTS

NOD2 activation resulted in the production of IFN-gamma within the eye. Deficiency in IFN-gamma diminished the development of MDP-induced uveitis, indicating its crucial role in downstream inflammatory events triggered by NOD2. Moreover, exogenous IFN-gamma markedly exacerbated MDP-induced ocular inflammation in a NOD2-dependent mechanism. The potential of IFN-gamma to enhance inflammation required the adhesion molecule CD11b because CD11b-deficient mice failed to show the synergistic effects of IFN-gamma and MDP cotreatment on adhering and infiltrating cells.

CONCLUSIONS

IFN-gamma was identified as a downstream mediator of NOD2-driven inflammation and the capacity of IFN-gamma in vivo to enhance the inflammatory potential of NOD2 was demonstrated. Extrapolation of these findings in mice suggests that the dysregulation of IFN-gamma may occur in patients with Blau syndrome, thereby contributing to the granulomatous nature of the disease.

[Hereditary systemic autoinflammatory diseases. Part II: cryopyrin-associated periodic syndromes, pediatric systemic granulomatosis and PAPA syndrome]

Hereditary systemic autoinflammatory diseases result from a genetically-based dysregulated inflammatory process, and are clinically characterized by recurrent or persistent systemic inflammatory episodes, which typically occur in the absence of infectious, neoplastic or autoimmune etiology. Elucidation of their molecular basis has enabled the use of genetic analyses to achieve an accurate and definitive diagnosis, and to establish a tailored treatment. The present review is the second and last part of an updated and comprehensive overview of hereditary systemic autoinflammatory diseases, and will introduce persistent, non-periodic autoinflammatory diseases, such as: a) the group of cryopyrin-associated periodic syndromes (CAPS), which includes familial cold-induced autoinflammatory syndrome (FCAS), Muckle-Wells syndrome, and CINCA-NOMID syndrome; b) the group of pediatric systemic granulomatosis, which includes both Blau syndrome and early-onset sarcoidosis, and c) the pyogenic sterile arthritis, pyoderma gangrenosum and acne (PAPA) syndrome.

Clinical and genetic aspects of Blau syndrome: a 25-year follow-up of one family and a literature review

Blau syndrome (BS) is a rare familial disease transmitted as an autosomal dominant trait, characterized by arthritis, uveitis, skin rash and granulomatous inflammation. Until now BS has been observed in 136 persons belonging to 28 families as well as in 4 sporadic cases. The gene responsible for BS has recently been identified in the nucleotide-binding domain (NBD) of caspase recruitment domain (CARD15/NOD2), also involved in the pathogenesis of Crohn's disease. In addition to three missense mutations (R334Q, R334W and L469F) previously identified, a new CARD 15 mutation (E383K) has recently been described in a family followed by us for the past 25 years. The characteristics of this family which, to our knowledge, is the only one affected with BS in Italy, are the object of this manuscript. Both the proband and her daughter were originally affected with a papulonodular skin eruption and then with mild arthritis of the hands and feet. The proband, but not the daughter, complained of severe chronic bilateral uveitis, followed by glaucoma and, a few years later, by cataracts. Histological examination of skin biopsies from both subjects and a joint biopsy (daughter only), showed non-caseating granulomas with multinucleated giant cells which, at electron microscopy, revealed "comma-shaped bodies" in epithelioid cells, thought to be a marker for BS. The disease is presently well controlled with low doses of prednisone for the mother and non-steroidal anti-inflammatory drugs (NSAIDs) plus low doses of prednisone, when necessary, for the daughter. As in Crohn's disease, CARD15/NOD2 mutation is believed to be responsible for the granulomatous autoinflammatory reactions probably triggered by microorganisms in BS.

The NLR network and the immunological disease continuum of adaptive and innate immune-mediated inflammation against self

The nucleotide-binding domain, leucine-rich repeat containing family (NLR) network has provided pivotal genetic and molecular insights into diseases that were hitherto regarded as autoimmune. The NLR-related disorders include rare monogenic autoinflammatory diseases collectively termed cryopyrin-associated periodic syndromes, Crohn's disease which is a common polygenic disease and also an association at the mechanistic level with gout and pseudogout. Unlike the classical autoimmune diseases where disease immunopathogenesis is played out primarily in the primary and secondary lymphoid organs, the immunopathogenesis of the NLR-related disorders is played out in the tissues where inflammation arises. As the genetic mutations or molecular cascades associated with the NLR-related disorders have a widespread cellular distribution, it has been somewhat enigmatic why these disorders attack certain territories, but not others. This implies that tissue-specific factors in the target organs themselves contribute to disease expression. Such examples include the high abundance of NOD2 expressing cells in the part of the gut most typically afflicted by Crohn's disease and the preferential deposition of crystals in the joints to where inflammation localises in gout and pseudogout. The NLR network is associated principally with increases in TNF or IL-1 production, both of which are key players in innate immunity. Therefore, the NLR network identifies at the genetic and molecular level a robust paradigm for innate immune activation against self. This tissue-specific-factor-associated inflammation is the diametric opposite of classical autoimmunity. Of note, the MHC class-I-associated diseases including psoriasis (HLA-Cw6) and ankylosing spondylitis (HLA-B27) show striking clinical overlaps with Crohn's disease and also some rare monogenic diseases. Thus, the NLR innate immune pathway allows the full spectrum of inflammation against self to be viewed along an immunological disease continuum with autoantibody-associated disease at one end, innate immune diseases at the other and MHC class-1-related disorders as an intermediate.

From inflammasomes to fevers, crystals and hypertension: how basic research explains inflammatory diseases

Pattern-recognition receptors, such as Toll-like receptors and NOD-like receptors (NLRs), are able through the recognition of pathogen-associated molecular patterns and danger-associated molecular patterns to sense microbe-dependent and microbe-independent danger and thereby initiate innate immune responses. In some autoinflammatory conditions, abnormalities in NLR signaling pathways are involved in pathogenesis, as exemplified by NOD2 mutations associated with Crohn's disease. Some other NLRs are components of the inflammasome, a caspase-1- and prointerleukin-1beta-activating complex. Clinical and experimental studies are beginning to reveal the central role of the inflammasome in innate immunity. Here, we focus on monogenic hereditary inflammatory diseases, such as Muckle-Wells syndrome, which are associated with mutations in proteins that modulate the activity of the inflammasome, and on some multifactorial disorders, such as Type 2 diabetes and hypertension.

Chronic inflammation: importance of NOD2 and NALP3 in interleukin-1beta generation

Inflammation is part of the non-specific immune response that occurs in reaction to any type of bodily injury. In some disorders, the inflammatory process - which under normal conditions is self-limiting - becomes continuous and chronic inflammatory diseases might develop subsequently. Pattern recognition molecules (PRMs) represent a diverse collection of molecules responsible for sensing danger signals, and together with other immune components they are involved in the first line of defence. NALP3 and NOD2, which belong to a cytosolic subgroup of PRMs, dubbed Nod-like-receptors (NLRs), have been associated recently with inflammatory diseases, specifically Crohn's disease and Blau syndrome (NOD2) and familial cold autoinflammatory syndrome, Muckle-Wells syndrome and chronic infantile neurological cutaneous and articular syndrome (NALP3). The exact effects of the defective proteins are not fully understood, but activation of nuclear factor (NF)-kappaB, transcription, production and secretion of interleukin (IL)-1beta and activation of the inflammasome are some of the processes that might hold clues, and the present review will provide a thorough update in this area.

Clinical features of Blau syndrome and early-onset sarcoidosis and associating CARD15/NOD2 gene mutations

Sarcoidosis is a systemic inflammatory disease clinically characterized by swelling of bilateral hilar lymph nodes and histologically defined by non-caseating epithelioid cell granulomas. Among child cases, a special subtype, called the early-onset sarcoidosis, is known to appear in children younger than 4 years of age and to be characterized by a distinct triad of skin, joint and eye disorders without pulmonary involvement. On the other hand, autosomal dominantly-transmitted disease with a characteristic features similar to those of early-onset sarcoidosis has been reported as Blau syndrome. By a linkage analysis, the responsible gene for Blau syndrome has been mapped close to the IBD (Inflammatory Bowel Disease) 1 locus. After CARD15 (NOD2), originally identified as the susceptibility gene for Crohn's disease, was also proved to be responsible for Blau syndrome, the same gene mutations have been found in sporadic early-onset sarcoidosis cases. Nod2 recognizes a signal from bacterial cell wall component in the cytoplasm of monocytic cells to activate NF-kappaB, and thus can work as an intracellular sensor of bacteria. While the loss-of-function mutations in its LRR domain are associated with Crohn's disease, Blau syndrome and early-onset sarcoidosis are autoinflammatory diseases that are caused by the gain-of-function mutations in its NOD domain.

Favourable effect of TNF-α inhibitor (infliximab) on Blau syndrome in monozygotic twins with ade novoCARD15mutation

Blau syndrome is a hereditary granulomatous disease caused by mutations in the CARD15 gene that is diagnosed in children of young age with exanthema/erythema, arthritis/periarthritis and/or uveitis. We report two cases of Blau syndrome in Danish Caucasian monozygotic male twins, exhibiting a heterozygous de novo R334W mutation in codon 334 of CARD15. The patients were initially diagnosed as having sarcoidosis. In both twins, symptoms (exanthema, arthritis/periarthritis) started at 1 year of age, and were followed by uveitis at 7-10 years of age. There was no involvement of the lungs or other organs. An initial course of standard antituberculous treatment had no effect on the symptoms. Hydroxychloroquine and cyclosporine A were also ineffective, and the latter caused impaired renal function. Partial symptomatic relief was obtained with prednisolone and increased benefit was observed in combination with methotrexate. Subsequent introduction of the TNF-alpha inhibitor eternacept did not discernibly benefit the clinical condition, but was associated with recurrent infections. In contrast, a trial of infliximab therapy demonstrated clinical efficacy and eliminated all symptoms, restoring a high quality of life. At follow up at 20 years of age (after 2-5 years of infliximab treatment) the twins had an almost normal physical appearance and a normal psychomotoric development, indicating a favourable short-term prognosis of the disease. Blau syndrome has pathologic, clinical and therapeutic features in common with sarcoidosis, but rarely involves the lungs or other parenchymatous organs. In children, discrimination between early onset sarcoidosis and Blau syndrome should include a CARD15 mutation analysis.

Pediatric granulomatous arthritis: An international registry

OBJECTIVE

Blau syndrome and its sporadic counterpart, early-onset sarcoidosis, share an identical phenotype featuring the classic triad of arthritis, dermatitis, and uveitis and are associated with mutations of CARD15 in 50-90% of cases. We chose the term "pediatric granulomatous arthritis" to refer to both. An international registry was established in the spring of 2005 to define the phenotype spectrum and establish the mutation frequency and variants.

METHODS

Histologically confirmed granuloma and arthritis were required for inclusion. Probands and relatives were genotyped for CARD15. Deidentified clinical information was collected.

RESULTS

One year after the inception of the registry, 61 individuals from 22 pedigrees had been entered. Seven pedigrees with 19 individuals (8 affected, 11 unaffected) had clinical disease that was atypical, and none of the individuals in those pedigrees showed mutations. There were 9 classic simplex pediatric granulomatous arthritis pedigrees including 19 individuals (9 affected, 10 unaffected) and 6 classic multiplex pedigrees with 22 individuals (17 affected, 5 unaffected). Cutaneous presentation was the most common. Arthritis was polyarticular in 96% of patients. Isolated eye disease was never the presenting symptom, but significant/severe visual impairment was observed in 41% of patients. Eye disease was bilateral in 21 of 22 patients and was complicated by glaucoma in 6 of 22 patients and by cataracts in 50% of patients. Skin biopsy was the best diagnostic approach (because of accuracy and low invasiveness).

CONCLUSION

In this series, the first combining familial and sporadic pedigrees and, to our knowledge, the largest, we further defined the phenotype and showed that all affected classic (and no nonclassic) pedigrees carry a mutation and that there is no asymptomatic carriage. If these data are confirmed, mutation analysis rather than tissue sampling may prove to be the most efficient diagnostic procedure.

Blau syndrome and related genetic disorders causing childhood arthritis

Blau Syndrome (BS) is an inheritable disorder characterized by granulomatous polyarthritis, panuveitis, and exanthema. It was described by Edward Blau in 1985, the same year in which Douglas Jabs reported a very similar family. Clinically indistinguishable from early onset sarcoidosis (EOS), both are now known to share a mutated form of caspase recruitment domain-15 (CARD 15), a protein involved in activation of nuclear factor kappa B which is in turn an up-regulator of pro-inflammatory cytokine transcription. An association between BS and EOS was suspected for years given the striking similarities of the core triad (arthritis-uveitis-dermatitis) and a common emerging pattern of systemic involvement. Hence, the familial form (BS) and the sporadic form (EOS) are almost certainly the same illness/defect, inherited in the first and acquired in the second as a result in most cases of a de novo mutation. Another form of granulomatous arthritis with uveitis, Crohn's disease, has also been associated with mutations in CARD 15 (albeit at a different domain) and despite similar phenotypes there are obvious differences including gut inflammation and pyoderma gangrenosum in Crohn's disease. This paper will review the clinical characteristics of these three disorders and their association with mutations in the CARD 15 gene.

Caspase recruitment domain 15 mutations and rheumatic diseases

PURPOSE OF REVIEW

The purpose of this article is to review the foundational work and current developments on a group of rheumatic disorders associated with mutations in the caspase recruitment domain 15/nucleotide oligomerization domain 2 gene.

RECENT FINDINGS

To date, there are at least 10 arthritic conditions for which specific genetic mutations have been demonstrated. They include familial Mediterranean fever; tumor necrosis factor receptor associated periodic syndrome; hyper immunoglobulin D syndrome; neonatal onset multisystemic inflammatory disease; pyogenic arthritis pyoderma gangrenosum and acne; Muckle-Wells syndrome; familial cold autoinflammatory syndrome; immunodysregulation, polyendocrinopathy, enteropathy, X-linked syndrome; Crohn's disease; and familial and sporadic sarcoid granulomatous arthritis. This review focuses on recent progress in the last two diseases and the caspase recruitment domain 15 genetic defects with which they are associated. Up to 50% of patients with familial granulomatous arthritis (Blau's syndrome), 90% of those with sporadic granulomatous arthritis (early-onset sarcoidosis), and 40% of individuals with Crohn's disease have documented mutations in the caspase recruitment domain 15 gene.

SUMMARY

Although histologically, Crohn's disease and familial and sporadic sarcoid granulomatous arthritis are distinct from rheumatoid arthritis because of the defining presence (albeit in not all cases) of non-caseating granulomata in the synovial and intestinal tissues, respectively, they still represent a promising model of both chronic synovitis and uveitis. In addition, once the actual mechanism is discovered by which defects of the caspase recruitment domain 15 gene product lead to chronic arthritis, it may uncover unsuspected biologic targets for therapeutics.

The cytosolic pattern-recognition receptor Nod2 and inflammatory granulomatous disorders

Pattern-recognition receptors are a first line of defense against invading pathogens. Recent advances in the understanding of innate immunity have revealed a novel family of cytosolic pattern-recognition receptors called Nods, which contain an amino-terminal effector-binding domain, a centrally located nucleotide-binding oligomerization domain (NOD) and a carboxy-terminal ligand recognition domain. Hereditary mutations of Nods have been reported in patients with certain inflammatory diseases; for example, Nod2 mutations are associated with the inflammatory granulomatous disorders, Crohn's disease and Blau syndrome. Missense mutations of Nod2 are also associated with early-onset sarcoidosis, a rare but sporadic disease. Because Nod2 is predominantly expressed in monocytes and recognizes a component of bacterial peptidoglycan, analysis of its function may help in understanding the role of the immune system in granuloma formation.

Blau syndrome presenting with ichthyosis

A 12-year-old girl presented with uveitis, joint disease and ichthyosis resembling ichthyosis vulgaris. A biopsy taken from the affected lower leg demonstrated sarcoidal-type granulomas. Synovial biopsy from the knee also showed granulomas. There was a family history of similar clinical features in the patient's younger sister. There were no other systemic features present to suggest a diagnosis of sarcoidosis or other granulomatous disease such as Crohn's disease or tuberculosis. The familial nature of the condition also made these diagnoses less likely. A clinical diagnosis of Blau syndrome was made. Blau syndrome is an uncommon sarcoidosis-like multisystem autosomal-dominant granulomatous disorder caused by mutations in the CARD15 gene. This gene has also recently been found to be a factor in the development of psoriatic arthritis and Crohn's disease. Although many forms of skin involvement have been described in Blau syndrome, this is the first case described of ichthyosis as the primary skin manifestation.

Ocular manifestations in Blau syndrome associated with a CARD15/Nod2 mutation

PURPOSE

To report cases of Blau syndrome with a CARD15/Nod2 mutation.

DESIGN

Observational and interventional case report.

PARTICIPANTS

A 10-year-old Japanese boy (proband) was seen with secondary angle-closure glaucoma (iris bombe), uveitis, skin rashes, and camptodactyly. His sister had posterior synechia and camptodactyly. She had iritis in both eyes during the follow-up period. Both eyes of the father were phthisical because of granulomatous uveitis and secondary glaucoma. The father also had camptodactyly.

METHODS

Surgery was performed to release the iris bombe. Ocular inflammation was treated by topical and systemic steroids. Biopsy specimens from the skin rash and from the iris (from iridectomy) were obtained from the proband. Genetic analyses were performed on the proband, his sister, and their mother for a CARD15/Nod2 mutation.

MAIN OUTCOME MEASURES

Clinical features, pathologic findings of the skin and iris specimens, and genetic analysis of the CARD15/Nod2 gene.

RESULTS

Phacoemulsification, intraocular lens implantation, and peripheral iridectomy released the iris bombe. The biopsy specimen from the skin rash showed noncaseating, granulomatous infiltration with epithelioid cells and lymphocytes. The iridectomy specimen showed nonspecific inflammation. Systemic and topical steroid therapy partly reduced the ocular inflammation. Genetic analyses showed that the proband and his sister had an R334W mutation in the CARD15/Nod2 gene, but their mother was of the wild type.

CONCLUSIONS

Blau syndrome should be considered in the differential diagnosis of childhood uveitis. Genetic analysis of the CARD15/Nod2 gene is helpful in the diagnosis.

Blau syndrome: a new kindred

Blau syndrome is a rare condition typically defined by granulomatous arthritis, skin eruption, and uveitis occurring in the absence of lung or other visceral involvement. Other characteristic physical findings include synovial cysts and camptodactyly. We describe a new kindred demonstrating autosomal dominant inheritance and anticipation.

Multifocal choroiditis in patients with familial juvenile systemic granulomatosis

PURPOSE

To document clinical features of uveitis in patients with familial juvenile systemic granulomatosis.

DESIGN

Retrospective chart review.

METHODS

Ophthalmologic examination, medical history, and clinical course in 16 patients from eight families examined at six academic medical centers.

RESULTS

Of the 16 patients, 15 had evidence of panuveitis with multifocal choroiditis. One patient had only an anterior uveitis. Ischemic optic neuropathy, presumably due to a small vessel vasculopathy, and retinal vasculopathy each occurred in one patient. Ocular complications were common, including cataracts in 11, glaucoma in six, band keratopathy in six, cystoid macular edema in six, and optic disk edema in six. All 16 patients had polyarthritis, and at least nine had skin rash. Often patients were misdiagnosed initially as having either juvenile rheumatoid arthritis or sarcoidosis.

CONCLUSIONS

Familial juvenile systemic granulomatosis is an uncommon genetic disease characterized by polyarthritis and uveitis. Panuveitis and multifocal choroiditis often may be present. Patients with a diagnosis of juvenile rheumatoid arthritis but having a family history of the disease and multifocal choroiditis should be suspected of having familial juvenile systemic granulomatosis.

Evaluation of Th-1 and Th-2 immune responses in the skin lesions of patients with Blau syndrome

Blau syndrome is an autosomal dominant syndrome characterized by arthritis, uveitis, skin rash, granuloma, and camptodactyly. It has overlapping symptoms with sarcoidosis and rheumatoid arthritis. Our study was directed toward determining the role of cytokines in granuloma formation in Blau syndrome. Antigenic stimulation usually follows two pathways: Th-1, which activates macrophages and cytotoxic T-lymphocytes and produces interleukin (IL)-2, IL-3, interferon gamma, and tumor necrosis factor alpha, and Th-2, which activates the humoral immune system and produces IL-4, IL-5, and IL-10. The development of cytokine profiles may shed some light on our understanding of this illness. Therefore, we studied the relative roles of two opposing lymphocytes, Th-1 and Th-2, by analyzing their relative expression in the skin lesions of patients with Blau syndrome, using the in situ reverse transcription-polymerase chain reaction technique. Our data revealed a significant upregulation of IL-2, an event that appears to play an important role in the formation of granuloma and in the pathogenesis of Blau syndrome. Expression of IL-10, however, was downregulated, and this may have an inhibitory role in the development of the disease. Further studies would be necessary to confirm the presence of other cytokines and to establish the regulatory roles of Th-1 and Th-2 lymphocytes in the pathogenesis of Blau syndrome.

Sarcoidosis: a pediatric perspective

Childhood sarcoidosis is a rare multisystemic granulomatous disease of unknown etiology. The clinical presentation can vary greatly depending upon the organs involved. Two distinct forms of sarcoidosis exist in children. Older children usually present with a multisystem disease similar to the adult manifestation, with frequent hilar lymphadenopathy and pulmonary infiltration. Early-onset childhood sarcoidosis is a unique form of the disease characterized by the triad of rash, uveitis, and arthritis in patients presenting before age 4 years. The diagnosis of sarcoidosis is confirmed by demonstrating a typical noncaseating granuloma on a biopsy specimen. The current therapy of choice for childhood sarcoidosis with multisystem involvement is corticosteroids. Methotrexate given orally in low doses is effective and safe and has steroid-sparing properties.

Familial granulomatous arthritis (Blau syndrome) with granulomatous renal lesions

Blau syndrome is a granulomatous disease of the skin, eyes, and joints, usually without visceral involvement. It is inherited in a autosomal dominant manner. The Blau susceptibility locus has been mapped to chromosome 16 p 12-q21. A recent report has added liver granulomata. We describe a family with Blau syndrome in whom 1 member had renal interstitial granulomata.

Familial juvenile systemic granulomatosis (Blau's syndrome)

Blau's syndrome refers to the rare familial presentation of a sarcoid-like granulomatous disease classically involving the skin, uveal tract and joints, in the absence of pulmonary manifestations. The onset is in childhood, and the mode of inheritance is thought to be autosomal dominant. We report a 15-year-old female and her 22-month-old daughter who presented with clinical features similar to those of Blau's syndrome. In addition to the skin, eye and joint disease, the mother also developed neurological involvement. In both patients long-term systemic corticosteroids were required to control the disease.

Synovial cysts and ganglia: the value of magnetic resonance imaging

Synovial and ganglion cysts commonly present in close proximity to joints and skeletal structures in rheumatic disorders. Familiarity with the presentation of these soft tissue masses can facilitate timely diagnosis and effective management, thus avoiding costly and potentially high-risk procedures to patients. Management usually consists of local, nonsurgical approaches. A patient with chronic joint deformities and clinical features primarily consistent with mixed connective tissue disease is described. Multiple localized masses developed at her right elbow and were identified on T2-weighted magnetic resonance imaging as multiloculated cysts that dissected from the elbow joint. The cysts were treated successfully by needle aspiration and intraarticular corticosteroid injection. The clinical associations, diagnosis, treatment, and management of synovial cysts and ganglions are reviewed.