Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review

Working the endless puzzle of hereditary autoinflammatory disorders

Hereditary autoinflammatory disorders encompass manifold dysfunctions of innate immunity caused by mutations in genes coding for the main characters of the inflammatory scene: most of these conditions have an early onset, ranging from the first days of life to the first decades, and include hereditary periodic fevers, NLRP-related diseases, granulomatous and pyogenic syndromes, which are basically characterized by upturned inflammasome activity and overproduction of bioactive interleukin (IL)-1β and other proinflammatory cytokines. The discovery of a causative link between autoinflammation and IL-1β release has improved our understanding of the intimate mechanisms of innate immunity, and has likewise led to the identification of extraordinary treatments for many of these disorders.

Pustulotic arthro-osteitis associated with palmoplantar pustulosis

Palmoplantar pustulosis (PPP) is a chronic inflammatory disorder characterized by sterile pustules predominantly involving the palms and soles of middle-aged women. PPP frequently develops or exacerbates following focal infections, such as tonsillitis, odontogenic infection and sinusitis, either with or without arthralgia and/or extra-palmoplantar lesions. Pustulotic arthro-osteitis (PAO) is a joint comorbidity of PPP, most often affecting the anterior chest wall. PAO is sometimes regarded as the same entity as synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO) syndrome, and may be a subtype or incomplete type of SAPHO syndrome; however, there are several differences. In Japanese patients, PPP with PAO is frequently seen, whereas SAPHO syndrome in the true meaning is rare. A difference of incidence depending on race suggests that different genetic backgrounds may be responsible for susceptibility to these disorders. Bacterial infection, especially Propionibacterium acnes, is suggested to play an important role in the pathogenesis of SAPHO syndrome. P. acnes is responsible for acne, however, bacterium is unassociated with PPP skin lesions which are characterized by sterile pustules. On the other hand, PAO is frequently triggered by focal infection, and treatment of focal infection results in dramatic effects on the release of joint pain. This paper reviews current insights into the clinicopathophysiology of PAO, and discusses its possible mechanisms in comparison with SAPHO syndrome.

Associated factors and comorbidities in patients with pyoderma gangrenosum in Germany: a retrospective multicentric analysis in 259 patients

Background

Pyoderma gangrenosum (PG) is a rarely diagnosed ulcerative neutrophilic dermatosis with unknown origin that has been poorly characterized in clinical studies so far. Consequently there have been significant discussions about its associated factors and comorbidities. The aim of our multicenter study was to analyze current data from patients in dermatologic wound care centers in Germany in order to describe associated factors and comorbidities in patients with PG.

Methods

Retrospective clinical investigation of patients with PG from dermatologic wound care centers in Germany.

Results

We received data from 259 patients with PG from 20 different dermatologic wound care centers in Germany. Of these 142 (54.8%) patients were female, 117 (45.2%) were male; with an age range of 21 to 95 years, and a mean of 58 years. In our patient population we found 45.6% with anemia, 44.8% with endocrine diseases, 12.4% with internal malignancies, 9.3% with chronic inflammatory bowel diseases and 4.3% with elevated creatinine levels. Moreover 25.5% of all patients had a diabetes mellitus with some aspects of potential association with the metabolic syndrome.

Conclusions

Our study describes one of the world’s largest populations with PG. Beside the well-known association with chronic bowel diseases and neoplasms, a potentially relevant new aspect is an association with endocrine diseases, in particular the metabolic syndrome, thyroid dysfunctions and renal disorders. Our findings represent clinically relevant new aspects. This may help to describe the patients’ characteristics and help to understand the underlying pathophysiology in these often misdiagnosed patients.

Skin rash and arthritis a simplified appraisal of less common associations

Skin and joint manifestations are part of the clinical spectrum of many disorders. Well-known associations include psoriatic arthritis and arthritis associated with autoimmune connective tissue diseases. This review focuses on less common associations where skin lesions can provide easily accessible and valuable diagnostic clues, and directly lead to the specific diagnosis or limit the list of possibilities. This may also affect health care resources as diagnostic tests are often low-specific, highly expensive and poorly available. This group of diseases can be divided into two subsets, based on the presence/absence of fever, and then further classified according to elementary skin lesions (macular, urticarial, maculo-papular, vesico-bullous, pustular, petechial and nodular). In most instances joint involvement occurs as peripheral migrating polyarthritis. Erythematosus macular or urticarial rashes occur in most febrile disorders such as monogenic autoinflammatory syndromes, Schnitzler's syndrome, Still's disease and rheumatic fever and afebrile diseases as urticarial vasculitis. Pustular rash may be observed in chronic recurrent multifocal osteomyelitis (CRMO) and pyogenic arthritis with pyoderma gangrenosum and acne (PAPA) syndrome (both febrile) as well as in Behcet's disease and Synovitis, acne, pustulosis, hyperostosis and osteitis syndrome (both non-febrile). Papular lesions are typical of secondary syphilis, sarcoidosis, interstitial granulomatous dermatitis, papular petechial of cutaneous small-vessel vasculitis and nodular lesions of polyarteritis nodosa and multicentric reticulohistiocytosis all of which are afebrile. Differential diagnosis includes infections and drug reactions which may mimic several of these conditions. To biopsy the right skin lesion at the right time it is essential to obtain relevant histological information.

Autoinflammatory pustular neutrophilic diseases

This article provides a new categorization of inflammatory pustular dermatoses in the context of recent genetic and biological insights. Monogenic diseases with pustular phenotypes are discussed, including deficiency of interleukin 1 receptor antagonist, deficiency of the interleukin 36 receptor antagonist, CARD14-associated pustular psoriasis, and pyogenic arthritis, pyoderma gangrenosum, and acne. How these new genetic advancements may inform how previously described pustular diseases are viewed, including pustular psoriasis and its clinical variants, with a focus on historical classification by clinical phenotype, is also discussed.

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.

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.

Contribution of the inflammasomes to autoinflammatory diseases and recent mouse models as research tools

Inflammasomes are multiprotein complexes that serve as activating platforms for the enzyme caspase-1 in response to various danger signals. Active caspase-1 can cleave the precursors of the pro-inflammatory cytokines IL-1β and IL-18 and thereby activate them. Deregulation of this cascade caused by mutations in genes coding for inflammasomal components and their interaction partners can lead to severe disease. This review summarizes the contribution of deregulated inflammasomes to the field of autoinflammatory syndromes. In addition, it gives insight into currently available mouse models that are used to study and characterize the role of the inflammasome components in the pathophysiology of these diseases.

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.

Sterile Osteitis and Suppurative Arthritis Associated with Pannus Responding to Colchicine

Sterile suppurative arthritis is characterized by neutrophilic infiltration of joints without any causative pathogen. Here, we present a 32-year-old man with refractory osteitis and erosive suppurative oligoarthritis with pannus. Treatments with multiple disease modifying antirheumatic drugs were all unsuccessful. However, he had clinical response to colchicine and the synovial hypertrophy and the pannus in the MRI of his left shoulder resolved. In this case, the effects of colchicine on neutrophils might have played a role in treating neutrophilic sterile suppurative arthritis, which, in adults, might be a distinct oligoarticular disease.

Regulation of synaptojanin 2 5'-phosphatase activity by Src

Synaptojanin 2 (SYNJ2) is a phosphatidylinositol (PI) phosphatase that controls two distinct functions, clathrin-mediated endocytosis and tumor cell invadopodia formation and invasion. Here, we identify a number of novel SYNJ2 binding partners, several of which have previously been shown to be necessary for invadopodia formation or clathrin-mediated endocytosis. We focus on Src family kinases. We found that Src phosphorylates SYNJ2 on Tyr⁴⁹⁰, thereby stimulating SYNJ2 5′-phosphatase activity in vitro. We also provide evidence that Src-mediated phosphorylation of SYNJ2 contributes to invadopodia formation.