Blau syndrome and related genetic disorders causing childhood arthritis

Blau syndrome with hypertension and hepatic granulomas: a case report and literature review

Background

Blau syndrome (BS) is a monogenic disorder caused by NOD2 gene variants characterized by the triad of granulomatous polyarthritis, rash, and uveitis. Atypical symptoms were recognized in one-third to one-half of individuals with BS. This study aims to describe the clinical features of BS patients with hypertension and digestive system involvement.

Methods

The complete clinical data of a BS patient complicated with hypertension and hepatic granulomas were collected and documented. We also performed a literature search to find all reported cases of BS with hypertension and digestive system involvement.

Results

We reported the case of a 19-year-old man who presented with early onset symmetric polyarthritis and hypertension at age 5 and hepatic granulomas and cirrhosis at age 19. He was diagnosed with BS by the finding of a variant of the NOD2 gene (R334W). Through the literature review, 24 patients with BS were found who were reported to have hypertension, and 38 patients were found who had different digestive system manifestations such as hepatic granulomas, hepatosplenomegaly, diverticulitis, and intestinal granuloma. Among the 38 BS patients with digestive system involvement, 14 had hepatic granulomas proven by liver biopsy.

Conclusions

Hypertension and digestive system involvement are rare manifestations of BS. Clinicians, especially rheumatologists, must be aware of atypical symptoms of BS.

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.

Uveitis in Children and Adolescents

Childhood noninfectious uveitis leads to sight-threatening complications. Idiopathic chronic anterior uveitis and juvenile idiopathic arthritis-associated uveitis are most common. Inflammation arises from an immune response against antigens within the eye. Ophthalmic work-up evaluates anatomic involvement, disease activity, ocular complications, and disease course. Local and/or systemic glucocorticoids are initial treatment, but not as long-term sole therapy to avoid glucocorticoids-induced toxicity or persistent ocular inflammation. Children with recurrent, refractory, or severe disease require systemic immunosuppression with methotrexate and/or anti-tumor necrosis factor monoclonal antibody medications (adalimumab, infliximab). Goals of early detection and treatment are to optimize vision in childhood uveitis.

A novel mutation in early-onset sarcoidosis/Blau syndrome: an association with Propionibacterium acnes

BACKGROUND

Early-onset sarcoidosis (EOS) and Blau syndrome (BS) are systemic inflammatory granulomatous diseases without visible pulmonary involvement, and are distinguishable from their sporadic and familial forms. The diseases are characterized by a triad of skin rashes, symmetrical polyarthritis, and recurrent uveitis. The most common morbidity is ocular involvement, which is usually refractory to conventional treatment. A gain-of-function mutation in the nucleotide-binding oligomerization domain-containing protein 2 (NOD2) gene has been demonstrated in this disease; however, little is known about the relationship between the activation of NOD2 and the pathophysiology of EOS/BS. Here we describe EOS/BS with a novel mutation in the NOD2 gene, as well as detection of Propionibacterium acnes (P. acnes) in the granulomatous inflammation.

CASE PRESENTATION

An 8-year-old Japanese girl presented with refractory bilateral granulomatous panuveitis. Although no joint involvement was evident, she exhibited skin lesions on her legs; a skin biopsy revealed granulomatous dermatitis, and P. acnes was detected within the sarcoid granulomas by immunohistochemistry with P. acnes-specific monoclonal (PAB) antibody. Genetic analyses revealed that the patient had a NOD2 heterozygous D512V mutation that was novel and not present in either of her parents. The mutant NOD2 showed a similar activation pattern to EOS/BS, thus confirming her diagnosis. After starting oral prednisolone treatment, she experienced an anterior vitreous opacity relapse despite gradual prednisolone tapering; oral methotrexate was subsequently administered, and the patient responded positively.

CONCLUSIONS

We presented a case of EOS/BS with a novel D512V mutation in the NOD2 gene. In refractory granulomatous panuveitis cases without any joint involvement, EOS/BS should be considered as a differential diagnosis; genetic analyses would lead to a definite diagnosis. Moreover, this is the first report of P. acnes demonstrated in granulomas of EOS/BS. Since intracellular P. acnes activates nuclear factor-kappa B in a NOD2-dependent manner, we hypothesized that the mechanism of granuloma formation in EOS/BS may be the result of NOD2 activity in the presence of the ligand muramyl dipeptide, which is a component of P. acnes. These results indicate that recognition of P. acnes through mutant NOD2 is the etiology in this patient with EOS/BS.

Ocular manifestations of Blau syndrome

PURPOSE OF REVIEW

This article summarizes the systemic and ocular manifestations of Blau syndrome, its genetic basis, and reviews recently published literature.

RECENT FINDINGS

A large multicenter prospective case series is underway, with 3-year preliminary results indicating the prevalence of uveitis, clinical characteristics and early data on its visual prognosis. Case reports have demonstrated the successful use of newer biologic agents.

SUMMARY

Blau syndrome is an exceedingly rare autoinflammatory disorder with skin, joint and eye manifestations. It is caused by autosomal dominant mutations of the NOD2 protein. Eye involvement is typically a chronic bilateral granulomatous iridocyclitis, often with multifocal choroiditis in the posterior segment. Treatment starts with topical and systemic steroids and often requires antimetabolites or biologic agents.

Blau Syndrome and Early-Onset Sarcoidosis: A Six Case Series and Review of the Literature

Objectives

This study aims to discuss the clinical, laboratory and genetic findings, and treatment options for six patients who were diagnosed with Blau syndrome (BS)/early-onset sarcoidosis (EOS).

Patients and methods

The study included four patients (2 males,2 females; mean age 7 years; range 4 to 10 years) with EOS and two siblings (1 male, 1 female; mean age 10 years; range, 9 to 11 years) with BS. Age, age of initial symptoms, age of diagnosis; articular involvement, presence of uveitis, dermatitis, or fever, other organ involvement, laboratory findings, results of metabolic tests for mucopolysaccharidosis and mucolipidosis, results of genetic, pathologic, and immunologic tests, radiologic findings to evaluate skeletal dysplasia, and treatment options were collected.

Results

The median age at diagnosis of all patients was 6 years (range, 1 to 10 years). Five patients had camptodactyly and bilateral boggy synovitis in the wrists and ankles, one had granulomatous inflammatory changes in the liver and kidney biopsy, and one had attacks of fever and granulomatous dermatitis. None had uveitis. The detected mutations in nucleotide-binding oligomerization domain containing 2 (NOD2) were P268S (rs2066842), M513T (rs104895473), R702W (rs2066844), V955I (rs5743291), H343Y (rs199858111), and M491L (16:50745293). The treatments of patients included corticosteroids, non-steroid anti-inflammatory drugs, methotrexate, infliximab, adalimumab, anakinra, and canacinumab.

Conclusion

Camptodactyly and boggy synovitis are important signs of BS/EOS. Methotrexate and tumor necrosis factor blockers are more effective in patients with predominantly articular symptoms. In patients 5 and 6 and their mother, we determined a novel M491L mutation in the NOD2 gene. Currently, this work is in progress towards identifying the pathogenesis and treatment options for this disease.

Dermatologic and Dermatopathologic Features of Monogenic Autoinflammatory Diseases

Autoinflammatory diseases include disorders with a monogenic cause and also complex conditions associated to polygenic or multifactorial factors. An increased number of both monogenic and polygenic autoinflammatory conditions have been identified during the last years. Although skin manifestations are often predominant in monogenic autoinflammatory diseases, clinical and histopathological information regarding their dermatological involvement is still scarce. Monogenic autoinflammatory diseases with cutaneous expression can be classified based on the predominant lesion: (1) maculopapular rashes or inflammatory plaques; (2) urticarial rashes; (3) pustular, pyogenic or neutrophilic dermatosis-like rashes; (4) panniculitis or subcutaneous nodules; (5) vasculitis or vasculopathy; (6) hyperkeratotic lesions; (7) hyperpigmented lesions; (8) bullous lesions; and (9) aphthous lesions. By using this classification, this review intends to provide clinical and histopathological knowledge about cutaneous involvement in monogenic autoinflammatory diseases.

Granulomatous & histiocytic dermatitides

Granulomas of the skin may be classified in several ways. They are either infectious or non-infectious in character, and they contain areas of necrobiosis or necrosis, or not. Responsible infectious agents may be mycobacterial, fungal, treponemal, or parasitic organisms, and each case of granulomatous dermatitis should be assessed histochemically for those microbes. In the non-infectious group, examples of necrobiotic or necrotizing granulomas include granuloma annulare; necrobiosis lipoidica; rheumatoid nodule; and lupus miliaris disseminates faciei. Non-necrobiotic/necrotizing and non-infectious lesions are exemplified by sarcoidosis; foreign-body reactions; Melkersson-Rosenthal syndrome; Blau syndrome; elastolytic granuloma; lichenoid and granulomatous dermatitis; interstitial granulomatous dermatitis; cutaneous involvement by Crohn disease; granulomatous rosacea; and granulomatous pigmented purpura. Histiocytic dermatitides that do not feature granuloma formation are peculiar reactions to infection, such as cutaneous malakoplakia; leishmaniasis; histoplasmosis; lepromatous leprosy; rhinoscleroma; lymphogranuloma venereum; and granuloma inguinale.

Molecular mechanisms in genetically defined autoinflammatory diseases: disorders of amplified danger signaling

Patients with autoinflammatory diseases present with noninfectious fever flares and systemic and/or disease-specific organ inflammation. Their excessive proinflammatory cytokine and chemokine responses can be life threatening and lead to organ damage over time. Studying such patients has revealed genetic defects that have helped unravel key innate immune pathways, including excessive IL-1 signaling, constitutive NF-κB activation, and, more recently, chronic type I IFN signaling. Discoveries of monogenic defects that lead to activation of proinflammatory cytokines have inspired the use of anticytokine-directed treatment approaches that have been life changing for many patients and have led to the approval of IL-1-blocking agents for a number of autoinflammatory conditions. In this review, we describe the genetically characterized autoinflammatory diseases, we summarize our understanding of the molecular pathways that drive clinical phenotypes and that continue to inspire the search for novel treatment targets, and we provide a conceptual framework for classification.

A new mutation in blau syndrome

Blau syndrome is a rare, autosomal dominant, granulomatous autoinflammatory disease. The classic triad of the disease includes recurrent uveitis, granulomatous dermatitis, and symmetrical arthritis. Blau syndrome is related to mutations located at the 16q12.2-13 gene locus. To date, 11 NOD2 gene mutations causing Blau syndrome have been described. Here, we describe a 5-year-old male patient who presented with Blau syndrome associated with a novel sporadic gene mutation that has not been reported previously.

[Genetic risk profile of sarcoidosis]

Sarcoidosis is a multifactorial and polygenic disorder. The current knowledge of its genetic basis will be presented and functional consequences of the genetic variants that influence the immunopathogenesis of this disorder will be depicted. In the near future it is expected that this knowledge will yield clinically applicable genetic risk profiles.

IL-1 blockade in autoinflammatory syndromes

Monogenic autoinflammatory syndromes present with excessive systemic inflammation including fever, rashes, arthritis, and organ-specific inflammation and are caused by defects in single genes encoding proteins that regulate innate inflammatory pathways. Pathogenic variants in two interleukin-1 (IL-1)-regulating genes, NLRP3 and IL1RN, cause two severe and early-onset autoinflammatory syndromes, CAPS (cryopyrin associated periodic syndromes) and DIRA (deficiency of IL-1 receptor antagonist). The discovery of the mutations that cause CAPS and DIRA led to clinical and basic research that uncovered the key role of IL-1 in an extended spectrum of immune dysregulatory conditions. NLRP3 encodes cryopyrin, an intracellular "molecular sensor" that forms a multimolecular platform, the NLRP3 inflammasome, which links "danger recognition" to the activation of the proinflammatory cytokine IL-1β. The success and safety profile of drugs targeting IL -1 in the treatment of CAPS and DIRA have encouraged their wider use in other autoinflammatory syndromes including the classic hereditary periodic fever syndromes (familial Mediterranean fever, TNF receptor-associated periodic syndrome, and hyperimmunoglobulinemia D with periodic fever syndrome) and additional immune dysregulatory conditions that are not genetically well defined, including Still's, Behcet's, and Schnitzler diseases. The fact that the accumulation of metabolic substrates such as monosodium urate, ceramide, cholesterol, and glucose can trigger the NLRP3 inflammasome connects metabolic stress to IL-1β-mediated inflammation and provides a rationale for therapeutically targeting IL-1 in prevalent diseases such as gout, diabetes mellitus, and coronary artery disease.

Untangling the web of systemic autoinflammatory diseases

The innate immune system is involved in the pathophysiology of systemic autoinflammatory diseases (SAIDs), an enlarging group of disorders caused by dysregulated production of proinflammatory cytokines, such as interleukin-1β and tumor necrosis factor-α, in which autoreactive T-lymphocytes and autoantibodies are indeed absent. A widely deranged innate immunity leads to overactivity of proinflammatory cytokines and subsequent multisite inflammatory symptoms depicting various conditions, such as hereditary periodic fevers, granulomatous disorders, and pyogenic diseases, collectively described in this review. Further research should enhance our understanding of the genetics behind SAIDs, unearth triggers of inflammatory attacks, and result in improvement for their diagnosis and treatment.

Monogenic autoinflammatory diseases: concept and clinical manifestations

The objective of this review is to describe the clinical manifestations of the growing spectrum of monogenic autoinflammatory diseases including recently described syndromes. The autoinflammatory diseases can be grouped based on clinical findings: 1. the three classic hereditary "periodic fever syndromes", familial Mediterranean Fever (FMF); TNF receptor associated periodic syndrome (TRAPS); and mevalonate kinase deficiency/hyperimmunoglobulinemia D and periodic fever syndrome (HIDS); 2. the cryopyrin associated periodic syndromes (CAPS), comprising familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS) and neonatal-onset multisystem inflammatory disease (NOMID) or CINCA, and; 3. pediatric granulomatous arthritis (PGA); 4. disorders presenting with skin pustules, including deficiency of interleukin 1 receptor antagonist (DIRA); Majeed syndrome; pyogenic arthritis, pyoderma gangrenosum and acne (PAPA) syndrome; deficiency of interleukin 36 receptor antagonist (DITRA); CARD14 mediated psoriasis (CAMPS), and early-onset inflammatory bowel diseases (EO-IBD); 5. inflammatory disorders caused by mutations in proteasome components, the proteasome associated autoinflammatory syndromes (PRAAS) and 6. very rare conditions presenting with autoinflammation and immunodeficiency.

Bilateral parotitis as the initial presentation of childhood sarcoidosis

The differential diagnosis of bilateral parotid gland enlargement in children includes infectious, inflammatory, and neoplastic disorders. We present the case of a 13-year-old male who presented with a 5-week history of bilateral parotid swelling. On exam, both parotid glands were nontender, smooth, and diffusely enlarged. He had slightly elevated inflammatory markers, but other lab results were normal. A neck CT revealed symmetric enlargement of the parotid, submandibular, and sublingual glands. A chest CT revealed scattered peripheral pulmonary nodules and bilateral hilar adenopathy. A parotid gland biopsy showed multiple noncaseating granulomas with multinucleated giant cells surrounded by lymphocytes, consistent with the diagnosis of sarcoidosis. Special stains for acid-fast and fungal organisms were negative. Using this illustrative case, we discuss the differential diagnosis of bilateral salivary gland enlargement in children and review the etiology, diagnosis, clinical manifestations, and treatment of pediatric sarcoidosis.

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.

[Early onset pediatric sarcoidosis, diagnostic problems]

Sarcoidosis, a chronic multisystem inflammatory granulomatous disorder of unknown origin, is a rare disease in children. Two distinct clinical presentations of sarcoidosis in childhood are known. Older children usually show multisystem disease, close to the adult manifestation, with lung infiltration and frequent hilar lymphadenopathy. Prior to the age of 5, sarcoidosis reveals more frequently with the classical triad of rash, arthritis, and uveitis. Due to non-specific clinical features and the lack of a specific test, recognizing sarcoidosis can be difficult in the pediatric population. Moreover, unlike in adults, lung involvement is rare in pediatric sarcoidosis. Given the lack of a definitive blood test, the World Association of Sarcoidosis and Other Granulomatous disorders (WASOG) only recommends dosing the serum angiotensin-converting enzyme (ACE). Its level is usually higher in children than in adults, but an increased ACE may help in the diagnosis. The gold standard is a biopsy specimen with typical epithelioid gigantocellular granuloma without caseating necrosis granuloma, after other disorders known to cause granulomatous disease have been reasonably excluded. We report here the case of a 4.5-year-old male with the history of polyarthritis and uveitis, considered first as juvenile rheumatoid arthritis, followed 5 years later by cutaneous involvement, which led to reconsidering the diagnosis. There were no pulmonary clinical findings. Histology provided the diagnosis of sarcoidosis. He then developed dependence on steroids. The lack of the classical triad delayed the diagnosis several years. This case shows the pediatric singularity of sarcoidosis, which needs to be known so that early and appropriate follow-up can be conducted.

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.

Primary immunodeficiency diseases associated with neurologic manifestations

Primary immunodeficiency diseases (PID) are a heterogeneous group of inherited disorders of the immune system, predisposing individuals to recurrent infections, allergy, autoimmunity, and malignancies. A considerable number of these conditions have been found to be also associated with neurologic signs and symptoms. These manifestations are considered core features of some immunodeficiency syndromes, such as ataxia-telangiectasia and purine nucleoside phosphorylase deficiency, or occur less prominently in some others. Diverse pathological mechanisms including defective responses to DNA damage, metabolic errors, and autoimmune phenomena have been associated with neurologic abnormalities; however, several issues remain to be elucidated. Greater awareness of these associated features and gaining a better understanding of the contributing mechanisms will lead to prompt diagnosis and treatment and possibly development of novel preventive and therapeutic strategies. In this review, we aim to provide a brief description of the clinical and genetic characteristics of PID associated with neurologic complications.

The universe of immune deficiencies in Crohn's disease: a new viewpoint for an old disease?

Crohn's disease (CD) is generally considered a multifactorial disorder, since different genetic and environmental factors are thought to play a role in its pathogenesis. Recently, genome wide linkage studies allowed to identify the association of several loci with the increased risk of CD, although it is still unclear how they interact with environmental factors in causing the disease. The fact that many CD-risk-related genes are involved in the function of phagocytes seems in agreement with the well known role of these cells in CD histopathology. Functional defects in cytokine production or in clearance of bacteria in CD patients have recently been reported. Growing evidence that CD could arise from primary phagocyte immunodeficiency is also coming from the study of cases with early onset in infancy. We review such evidences starting from selected cases and discuss the clinical implications of these findings.

Sinus of valsalva aneurysm in Blau's syndrome

Blau syndrome is a rare granulomatous disorder inherited in an autosomal dominant manner characterized by the early appearance of granulomatous arthritis, skin rash and anterior uveitis. There are very few data on the cardiovascular manifestations of Blau syndrome. Here we report the first case of sinus of valsava aneurysm in Blau syndrome. In isolated unruptured aneurysms of a sinus of Valsalva without compromise of the aortic valve and/or the coronary ostia, repair may be accomplished by simple placation of the aneurysm or excision of the aneurysm(s) and patch closure of the defect(s) between the aortic annulus and the sinu-vascular ridge. Because of the particular conditions in our case, the repair was performed with replacement of the aortic valve and root using a composite graft employing a modified Bentall's technique.

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.

Dysregulation of innate immunity: hereditary periodic fever syndromes

The hereditary periodic fever syndromes encompass a rare group of diseases that have lifelong recurrent episodes of inflammatory symptoms and an acute phase response in common. Clinical presentation can mimic that of lymphoproliferative disorders and patients often go undiagnosed for many years. These syndromes follow an autosomal inheritance pattern, and the major syndromes are linked to specific genes, most of which are involved in regulation of the innate immune response through pathways of apoptosis, nuclear factor kappaBeta activation and cytokine production. In others, the link between the protein involved and inflammation is less clear. The recurrent inflammation can lead to complications, such as renal impairment due to amyloidosis and vasculitis, visual impairment, hearing loss, and joint destruction, depending on the specific syndrome. In recent years, treatment options for these diseases have improved significantly. Early establishment of an accurate diagnosis and start of appropriate therapy improves prognosis in these patients.

The spectrum of monogenic autoinflammatory syndromes: understanding disease mechanisms and use of targeted therapies

Monogenic autoinflammatory diseases encompass a distinct and growing clinical entity of multisystem inflammatory diseases with known genetic defects in the innate immune system. The diseases present clinically with episodes of seemingly unprovoked inflammation (fever, rashes, and elevation of acute phase reactants). Understanding the genetics has led to discovery of new molecules involved in recognizing exogenous and endogenous danger signals, and the inflammatory response to these stimuli. These advances have furthered understanding of innate inflammatory pathways and spurred collaborative research in rheumatology and infectious diseases. The pivotal roles of interleukin (IL)-1beta in cryopyrin-associated periodic syndromes, tumor necrosis factor (TNF) in TNF receptor-associated periodic syndrome, and links to inflammatory cytokine dysregulation in other monogenic autoinflammatory diseases have resulted in effective therapies targeting proinflammatory cytokines IL-1beta and TNF and uncovered other new potential targets for anti-inflammatory therapies.

The Nodosome: Nod1 and Nod2 control bacterial infections and inflammation

Toll-like receptors (TLRs) and the nucleotide-binding domain, leucine rich repeat containing family (or Nod-like receptors, NLRs) are two important families of microbial sensors that are membrane-associated and cytosolic molecules, respectively. The Nod proteins Nod1 and Nod2 are two NLR family members that trigger immune defense in response to bacterial peptidoglycan. Nod proteins fight off bacterial infections by stimulating proinflammatory signaling and cytokine networks and by inducing antimicrobial effectors, such as nitric oxide and antimicrobial peptides. Nod1 is also critically implicated in shaping adaptive immune responses towards bacterial-derived constituents. In addition, recent evidence has demonstrated that mutations in Nod1 and Nod2 are associated with a number of human inflammatory disorders, including Crohn's disease, Blau syndrome, early-onset sarcoidosis, and atopic diseases. Together, Nod1 and Nod2 represent central players in the control of immune responses to bacterial infections and inflammation.

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.

Pathogenesis of familial periodic fever syndromes or hereditary autoinflammatory syndromes

Familial periodic fever syndromes, otherwise known as hereditary autoinflammatory syndromes, are inherited disorders characterized by recurrent episodes of fever and inflammation. The general hypothesis is that the innate immune response in these patients is wrongly tuned, being either too sensitive to very minor stimuli or turned off too late. The genetic background of the major familial periodic fever syndromes has been unraveled, and through research into the pathophysiology, a clearer picture of the innate immune system is emerging. After an introduction on fever, interleukin-1beta and inflammasomes, which are involved in the majority of these diseases, this manuscript offers a detailed review of the pathophysiology of the cryopyrin-associated periodic syndromes, familial Mediterranean fever, the syndrome of pyogenic arthritis, pyoderma gangrenosum and acne, Blau syndrome, TNF-receptor-associated periodic syndrome and hyper-IgD and periodic fever syndrome. Despite recent major advances, there are still many questions to be answered regarding the pathogenesis of these disorders.