Etiology and management of pyoderma gangrenosum: a comprehensive review

Links between coagulation, inflammation, regeneration, and fibrosis in kidney pathology

Acute kidney injury (AKI) involves nephron injury leading to irreversible nephron loss, ie, chronic kidney disease (CKD). Both AKI and CKD are associated with distinct histological patterns of tissue injury, but kidney atrophy in CKD involves tissue remodeling with interstitial inflammation and scarring. No doubt, nephron atrophy, inflammation, fibrosis, and renal dysfunction are associated with each other, but their hierarchical relationships remain speculative. To better understand the pathophysiology, we provide an overview of the fundamental danger response programs that assure host survival upon traumatic injury from as early as the first multicellular organisms, ie, bleeding control by coagulation, infection control by inflammation, epithelial barrier restoration by re-epithelialization, and tissue stabilization by mesenchymal repair. Although these processes assure survival in the majority of the populations, their dysregulation causes kidney disease in a minority. We discuss how, in genetically heterogeneous population, genetic variants shift balances and modulate danger responses toward kidney disease. We further discuss how classic kidney disease entities develop from an insufficient or overshooting activation of these danger response programs. Finally, we discuss molecular pathways linking, for example, inflammation and regeneration or inflammation and fibrosis. Understanding the causative and hierarchical relationships and the molecular links between the danger response programs should help to identify molecular targets to modulate kidney injury and to improve outcomes for kidney disease patients.

Skin Signs of Rheumatoid Arthritis and its Therapy-Induced Cutaneous Side Effects

Rheumatoid arthritis (RA) is a systemic inflammatory disorder that primarily affects the joints, but may exhibit extra-articular, including cutaneous, manifestations such as rheumatoid nodules, rheumatoid vasculitis, granulomatous skin disorders, and neutrophilic dermatoses. A large burden of cutaneous disease may be an indication of RA disease activity and the need for more aggressive treatment. Many of the therapeutic agents used to treat RA can also result in cutaneous adverse effects, which pose their own diagnostic and therapeutic challenges. Anti-TNFα agents, in particular, have a wide variety of adverse effects including psoraisiform eruptions, granulomatous conditions, and cutaneous connective tissue disorders. Herein we provide an update on the clinical presentations and management of RA-associated cutaneous findings as well as drug-induced cutaneous effects, with particular attention to the adverse effects of biologic disease-modifying agents.

Pyoderma Gangrenosum: A Report of 27 Patients

The aim of this study was to document the profile of pyoderma gangrenosum (PG) patients who were treated in our clinic and to compare our patients' clinical and demographic characteristics with those described in the literature to help our understanding of the total burden of PG. A total of 27 (17 women, 10 men) patients with a mean age 48.6 years at diagnosis were included in the study. Seven (25.9%) of them had 3 or more ulcers. The lower extremity was the most common site of occurrence (92.5%). During the study period, 6 patients were admitted twice, and 7 were admitted 3 or more times (range 1 to >10), and the median length of stay was 27 days. A concomitant disease was present in PG patients especially in those between 20 and 40 years of age. Systemic therapy was used in 21 (91.3%) patients, 17 patients were treated with systemic corticosteroids, either alone in 7 patients or combination with other agents in 10 patients. Three of our patients died because of disease or treatment-related complications during the study period. Despite the high (70.3%) percentage of the PG patients with improving disease at the time of discharge, 1 year after hospital discharge, one third of our 27 patients still had PG requiring readmission. In conclusion, none of the current therapies provide satisfying results in all of the patients, and our data indicate a long-standing unmet need for effective therapy for the unexpected course of PG.

Premenstrual flares of pyoderma gangrenosum controlled with use of a combined oral contraceptive and antiandrogen (ethinyl estradiol/drospirenone)

The effect of sex hormones on pyoderma gangrenosum (PG) has not been reported. We report the case of a 34-year-old woman with chronic PG leg ulcers who was found to have recurring, premenstrual flares of PG. Her PG flares were controlled with the use of ethinyl estradiol/drospirenone.

Pyoderma gangrenosum and pregnancy: an example of abnormal inflammation and challenging treatment

Pyoderma gangrenosum (PG) is a neutrophil-predominant inflammatory disease that initially presents as a sterile pustule and may progress to ulcerations. Its root cause is unknown, but the presentation is commonly associated with systemic inflammatory conditions such as inflammatory bowel disease, arthritis and haematological abnormalities. On the other hand, pregnant women show a progressive neutrophilia during gestation, which culminates in a major inflammatory event to help drive labour. Although uncommonly, PG has been associated with pregnancy, which provides an additional link to systemic inflammation as an underlying cause of PG. We reviewed documented presentations of PG in gravid and post-partum patients, and have speculated on the possible pathogenesis based on their clinical presentations. Also, we summarize the reported treatments and their outcomes in these patients.

Pyoderma Gangrenosum Simulating Necrotizing Fasciitis

Pyoderma gangrenosum received this name due to the notion that this disease was related to infections caused by bacteria in the genus Streptococcus. In contrast to this initial assumption, today the disease is thought to have an autoimmune origin. Necrotizing fasciitis was first mentioned around the fifth century AD, being referred to as a complication of erysipelas. It is a disease characterized by severe, rapidly progressing soft tissue infection, which causes necrosis of the subcutaneous tissue and the fascia. On the third day of hospitalization after antecubital venipuncture, a 59-year-old woman presented an erythematous and painful pustular lesion that quickly evolved into extensive ulceration circumvented by an erythematous halo and accompanied by toxemia. One of the proposed etiologies was necrotizing fasciitis. The microbiological results were all negative, while the histopathological analysis showed epidermal necrosis and inflammatory infiltrate composed predominantly of dermal neutrophils. Pyoderma gangrenosum was considered as a diagnosis. After 30 days, the patient was discharged with oral prednisone (60 mg/day), and the patient had complete healing of the initial injury in less than two months. This case was an unexpected event in the course of the hospitalization which was diagnosed as pyoderma gangrenosum associated with myelodysplastic syndrome.

Pathophysiology of pyoderma gangrenosum (PG): an updated review

Pyoderma gangrenosum is a challenging skin condition to identify and treat because of its multifactorial pathogenesis. It is a rare cutaneous manifestation diagnosed clinically by exclusion of infection, neoplasia, thrombophilia, and other inflammatory conditions. Pathogenetic and treatment studies are scarce. Abnormalities in the function of inflammatory cytokines, the immune system, and neutrophils combined with specific genetic mutations predispose patients to develop this complex disease process. Early recognition of patients at risk for pyoderma gangrenosum, the necessity to improve its early diagnosis, and the future outlook of targeted and personalized therapies relies on the improved comprehension of the complex pathogenesis of pyoderma gangrenosum.

Pyoderma gangrenosum: An important dermatologic condition occasionally associated with rheumatic diseases

Pyoderma gangrenosum (PG) presents with refractory, sterile, deep ulcers most often on the lower legs. Clinically, PG exhibits four types, i.e., ulcerative, bullous, pustular, and vegetative types. PG may be triggered by surgical operation or even by minor iatrogenic procedures such as needle prick or catheter insertion, which is well-known as pathergy. PG is sometimes seen in association with several systemic diseases including rheumatoid arthritis (RA), inflammatory bowel disease, hematologic malignancy, and Takayasu’s arteritis. In particular, various cutaneous manifestations are induced in association with RA by virtue of the activation of inflammatory cells (neutrophils, lymphocytes, macrophages), vasculopathy, vasculitis, drugs, and so on. Clinical appearances of ulcerative PG mimic rheumatoid vasculitis or leg ulcers due to impaired circulation in patients with RA. In addition, patients with PG sometimes develop joint manifestations as well. Therefore, it is necessary for not only dermatologists but also rheumatologists to understand PG.

Intravenous immunoglobulin use in managing severe, perioperative peristomal pyoderma gangrenosum following subtotal colectomy with end ileostomy for medically refractory chronic ulcerative colitis

Peristomal pyoderma gangrenosum (PPG) is a rare subtype of pyoderma gangrenosum that is characterized by painful, necrotic ulcerations occurring in the area surrounding an abdominal stoma. PPG is typically seen in younger patients with active inflammatory bowel disease. The etiology and pathogenesis is largely unknown and risk factors are not well defined. Therapy typically involves a combination of aggressive local wound care and systemic medications. Diagnosis and management of PPG can be difficult and data on treatment are limited. We present a case of severe postoperative peristomal recalcitrant to conventional therapy successfully treated with intravenous immune globulin.

Periodic Fever and Neutrophilic Dermatosis: Is It Sweet's Syndrome?

A 7-year-old boy with high grade fever (39°C) and warm, erythematous, and indurated plaque above the left knee was referred. According to the previous records of this patient, these indurated plaques had been changed toward abscesses formation and then spontaneous drainage had occurred after about 6 to 7 days, and finally these lesions healed with scars. In multiple previous admissions, high grade fever, leukocytosis, and a noticeable increase in erythrocyte sedimentation rate and C-reactive protein were noted. After that, until 7th year of age, he had shoulder, gluteal, splenic, kidney, and left thigh lesions and pneumonia. The methylprednisolone pulse (30 mg/kg) was initiated with the diagnosis of Sweet's syndrome. After about 10-14 days, almost all of the laboratory data regressed to nearly normal limits. After about 5 months, he was admitted again with tachypnea and high grade fever and leukocytosis. After infusion of one methylprednisolone pulse, the fever and tachypnea resolved rapidly in about 24 hours. In this admission, colchicine (1 mg/kg) was added to the oral prednisolone after discharge. In the periodic fever and neutrophilic dermatosis, the rheumatologist should search for sterile abscesses in other organs.

Expression of cytokines, chemokines and other effector molecules in two prototypic autoinflammatory skin diseases, pyoderma gangrenosum and Sweet's syndrome

Pyoderma gangrenosum (PG) and Sweet's syndrome (SS) are two inflammatory skin diseases presenting with painful ulcers and erythematous plaques, respectively; both disorders have a debilitating clinical behaviour and PG is potentially life-threatening. Recently, PG and SS have been included among the autoinflammatory diseases, which are characterized by recurrent episodes of sterile inflammation, without circulating autoantibodies and autoreactive T cells. However, an autoinflammatory pattern clearly supporting this inclusion has never been demonstrated. We studied 16 patients with PG, six with SS and six controls, evaluating, using a sandwich-based protein antibody array method, the expression profile of inflammatory effector molecules in PG, SS and normal skin. The expressions of interleukin (IL)-1 beta and its receptor I were significantly higher in PG (P = 0·0001 for both) and SS (P = 0·004-0·040) than in controls. In PG, chemokines such as IL-8 (P = 0·0001), chemokine (C-X-C motif) ligand (CXCL) 1/2/3 (P = 0·002), CXCL 16 (P = 0·003) and regulated upon activation normal T cell expressed and secreted (RANTES) (P = 0·005) were over-expressed. In SS, IL-8 (P = 0·018), CXCL 1/2/3 (P = 0·006) and CXCL 16 (P = 0·036) but not RANTES were over-expressed, suggesting that chemokine-mediated signals are lower than in PG. Fas/Fas ligand and CD40/CD40 ligand systems were over-expressed in PG (P = 0·0001 for Fas, P = 0·009 for Fas ligand, P = 0·012 for CD40, P = 0·0001 for CD40 ligand), contributing to tissue damage and inflammation, while their role seems to be less significant in SS. Over-expression of cytokines/chemokines and molecules amplifying the inflammatory network supports the view that PG and SS are autoinflammatory diseases. The differences in expression profile of inflammatory effectors between these two disorders may explain the stronger local aggressiveness in PG than SS.

Neutrophilic skin lesions in autoimmune connective tissue diseases: nine cases and a literature review

The pathophysiology of neutrophilic dermatoses (NDs) and autoimmune connective tissue diseases (AICTDs) is incompletely understood. The association between NDs and AICTDs is rare; recently, however, a distinctive subset of cutaneous lupus erythematosus (LE, the prototypical AICTD) with neutrophilic histological features has been proposed to be included in the spectrum of lupus. The aim of our study was to test the validity of such a classification. We conducted a monocentric retrospective study of 7028 AICTDs patients. Among these 7028 patients, a skin biopsy was performed in 932 cases with mainly neutrophilic infiltrate on histology in 9 cases. Combining our 9 cases and an exhaustive literature review, pyoderma gangrenosum, Sweet syndrome (n = 49), Sweet-like ND (n = 13), neutrophilic urticarial dermatosis (n = 6), palisaded neutrophilic granulomatous dermatitis (n = 12), and histiocytoid neutrophilic dermatitis (n = 2) were likely to occur both in AICTDs and autoinflammatory diseases. Other NDs were specifically encountered in AICTDs: bullous LE (n = 71), amicrobial pustulosis of the folds (n = 28), autoimmunity-related ND (n = 24), ND resembling erythema gyratum repens (n = 1), and neutrophilic annular erythema (n = 1). The improvement of AICTDS neutrophilic lesions under neutrophil targeting therapy suggests possible common physiopathological pathways between NDs and AICTDs.

Pyoderma gangrenosum as a first presentation of inflammatory bowel disease

Up to 40% of patients with inflammatory bowel disease (IBD) develop an extraintestinal manifestation of the disease with the skin being the most commonly involved organ. Pyoderma gangrenosum (PG), an autoinflammatory non-infectious neutrophilic dermatosis, occurs in 1-2% of patients with IBD. PG can follow a course independent to that of the bowel disease, however, most reported cases describe PG occurring in patients with an established diagnosis of IBD. We present a case of a young patient who presented with axillary skin ulceration, which was subsequently diagnosed as PG. On further investigation for a possible underlying cause, she was found to have Crohn's disease. She had not developed any preceding change in her bowels and did not have abdominal pain; the IBD was diagnosed on endoscopic findings. This case is also unusual for the distribution of the PG lesions that typically occur in the lower limbs.

Fatal Case of Vulvar Pyoderma Gangrenosum with Pulmonary Involvement: Case Presentation and Literature Review

Introduction:

We report a case of a 61-year-old woman with locally destructive vulvar pyoderma gangrenosum (PG) with pulmonary involvement who was refractory to numerous systemic therapies and developed complications resulting in her demise.

Objective:

To report a rare case of treatment-resistant vulvar PG with pulmonary involvement that proved to be fatal.

Methods:

PubMed was used to search for other reports that discuss PG, or more specifically perigenital PG, with pulmonary involvement.

Results and Conclusion:

A thorough review of the literature revealed 33 cases of PG with pulmonary involvement, with only 4 involving the perigenital region. We report the second case of a female with vulvar PG and pulmonary involvement. In contrast to the first case described, our patient did not respond to systemic therapy, and, ultimately, her disease was fatal. It is hoped that with continued documentation of this rare and potentially lethal presentation of PG, physicians will determine more effective treatments.

Neutrophilic dermatoses: an update

Neutrophilic dermatoses constitute a heterogeneous group of dermatologic diseases, which are unified by the predominance of neutrophils within the inflammatory infiltrate on histopathology. The aims of this review were to provide an update on the clinical and histologic presentation of the main neutrophilic dermatoses and to develop a guide for clinical practice. A structured literature search of PubMed, Medline, and Embase was performed, using the key words "neutrophilic disorders", "cutaneous small vessel vasculitis", "Sweet's syndrome", "bowel associated dermatosis arthritis syndrome", "Behcet's", "palisaded neutrophilic and granulomatous dermatosis", "rheumatoid neutrophilic dermatitis", and "pyoderma gangrenosum". Related articles were screened for key terms and were included if appropriate. This group contains a wide spectrum of unique disorders, each with its own histologic and clinical subtleties, making specific diagnosis of a given entity within the group diagnostically challenging. The fact that overlapping forms of neutrophilic dermatoses, which share features of multiple neutrophilic dermatoses, are not uncommon makes the diagnoses more challenging.

Trends in the Association between Pyoderma Gangrenosum and Autoimmune Hepatitis: Case Report and Review of the Literature

Background:

Pyoderma gangrenosum (PG) is a neutrophilic dermatosis commonly associated with underlying systemic illness, typically of autoimmune origin. The association of PG with autoimmune hepatitis (AIH) has been reported but remains poorly recognized.

Observations:

We describe a case of PG manifesting 5 years following the diagnosis of AIH and conduct a literature review to determine the significance of this association. We identified a predisposition for young females and a tendency for PG to arise 4 to 12 years after the diagnosis of AIH during a period of disease quiescence. Additionally, fulminant hepatitis as the initial presentation of AIH appears to be a risk factor in the subsequent development of PG.

Conclusions:

These observations may provide important clues for the pathogenesis of PG in the context of AIH. Recognition of this association has important implications for dermatologists in the evaluation, workup, and management of patients with a history of AIH and suspected PG.

Use of dermal injection of activated protein C for treatment of large chronic wounds secondary to pyoderma gangrenosum

BACKGROUND

Pyoderma gangrenosum (PG) is a systemic disease that presents with cutaneous necrotizing ulceration, producing deep necrotic ulcers, usually with a raised, undermined, violaceous border. Treatment typically involves high dose immunosuppressive drugs, but more recently anti-tumour necrosis factor and monoclonal antibodies have been used. Activated protein C (APC) stimulates wound healing in patients with treatment-refractory skin ulcers, possibly by stimulating angiogenesis and re-epithelialization, and preventing inflammation.

AIM

To investigate whether APC may be beneficial as a treatment for ulcers related to cutaneous PG.

METHODS

Two patients were recruited with a clinical history and physical and histopathological evidence of acute PG. A total of 400 μg (1.0 mL) of APC was injected subcutaneously into the dermal edge of necrotic PG ulcers weekly for a total treatment period of 6 weeks. Photographs were taken, and clinical progress, ulcer size and pain score were monitored during this period and after the cessation of treatment, at weeks 8 and 12.

RESULTS

Over the 12 weeks of the trial, APC led to a reduction in wound size from 3.8 cm(2) to 0.8 cm(2) in patient 1 (78.9% decrease) and from 41 cm(2) to 16 cm(2) in patient 2 (70.0% decrease, respectively), and a reduction in pain scores from 10 to 0 (100% decrease) in both patients.

CONCLUSION

Although this study has limited because of its small sample size and lack of a true placebo group, it does indicate that APC has potential as a therapeutic option for patients with chronic skin ulcers from PG.

Rare association of pyoderma gangrenosum and palmoplantar pustulosis: a case report and review of the previous works

Pyoderma gangrenosum is a rare inflammatory, ulcerative skin disease that mainly involves the lower extremities. It frequently occurs in association with systemic diseases such as inflammatory bowel disease, myeloproliferative disorders and rheumatoid arthritis. Palmoplantar pustulosis is also an inflammatory dermatosis characterized by recurrent sterile pustules localized on the palms and soles. These two dermatoses are histologically characterized by neutrophilic infiltration into the lesional skin. Co-occurrence of pyoderma gangrenosum and palmoplantar pustulosis in a single patient is extremely rare. We report a case of pyoderma gangrenosum occurred in a patient with palmoplantar pustulosis, with a review of the previously reported cases. A 68-year-old Japanese woman with a 10-year history of palmoplantar pustulosis developed a skin ulcer on the left lower leg. The ulcer was diagnosed as pyoderma gangrenosum based on the clinical and histological findings, and rapidly improved in response to oral prednisolone. In addition to our case, five cases with palmoplantar pustulosis who developed pyoderma gangrenosum have been reported. These cases were thought to have some characteristics in common, such as marked female predominance, no association with inflammatory bowel disease and myeloproliferative disorders, and good response to less aggressive therapy. The co-occurrence of pyoderma gangrenosum and palmoplantar pustulosis in our case may have an etiological link, rather than being a coincidental complication.

Atypical pyoderma gangrenosum mimicking an infectious process

We present a patient with atypical pyoderma gangrenosum (APG), which involved the patient's arm and hand. Hemorrhagic bullae and progressive ulcerations were initially thought to be secondary to an infectious process, but a biopsy revealed PG. Awareness of APG by infectious disease services may prevent unnecessary use of broad-spectrum antibiotics.

Pyoderma gangrenosum: skin grafting and hyperbaric oxygen as adjuvants in the treatment of a deep and extensive ulcer

Pyoderma gangrenosum is a rare dermatosis of unknown etiology and variable clinical presentation. The disease is challenging for the medical staff, from the frequent diagnostic difficulties to the lack of scientific evidence with a good level to support the management of extensive and refractory cases. Our patient is a 50 year-old man with an extensive and deep ulcer on the left leg, which exemplifies the therapeutic difficulties inherent to the disease and who, fortunately, has progressed with excellent result after association of hyperbaric oxygen therapy and skin grafting to the immunosuppression therapy initially proposed.

Pyoderma gangrenosum successfully treated with antiretroviral therapy alone in a human immunodeficiency virus-infected individual

We report a case of a 60-year-old man infected with human immunodeficiency virus (HIV) who was transferred to our hospital for management of multiple non-healing, painful ulcers on the lower extremities. The histological findings of the biopsy specimen were compatible with the diagnosis of pyoderma gangrenosum (PG). An association between HIV infection and the development of PG was considered after a thorough investigation. Antiretroviral therapy without the use of adjunctive immunosuppressive agents resulted in clinical improvement. Our case implies that antiretroviral therapy alone could heal PG in untreated HIV-infected patients.

Autoinflammatory skin disorders in inflammatory bowel diseases, pyoderma gangrenosum and Sweet's syndrome: a comprehensive review and disease classification criteria

Pyoderma gangrenosum (PG) and Sweet's syndrome (SS) are skin diseases usually presenting with recurrent ulcers and erythematous plaques, respectively. The accumulation of neutrophils in the skin, characteristic of these conditions, led to coin the term of neutrophilic dermatoses to define them. Recently, neutrophilic dermatoses have been included in the group of autoinflammatory diseases, which classically comprises genetically determined forms due to mutations of genes regulating the innate immune response. Both PG and SS are frequently associated with inflammatory bowel diseases (IBDs); however, IBD patients develop PG in 1-3 % of cases, whereas SS is rarer. Clinically, PG presents with deep erythematous-to-violaceous painful ulcers with well-defined borders; bullous, pustular, and vegetative variants can also occur. SS is characterized by the abrupt onset of fever, peripheral neutrophilia, tender erythematous skin lesions, and a diffuse neutrophilic dermal infiltrate. It is also known as acute febrile neutrophilic dermatosis. Treatment of PG involves a combination of wound care, topical medications, antibiotics for secondary infections, and treatment of the underlying IBD. Topical therapies include corticosteroids and the calcineurin inhibitor tacrolimus. The most frequently used systemic medications are corticosteroids and cyclosporine, in monotherapy or in combination. Dapsone, azathioprine, cyclophosphamide, methotrexate, intravenous immunoglobulins, mycophenolate mofetil, and plasmapheresis are considered second-line agents. Hyperbaric oxygen, as supportive therapy, can be added. Anti-TNF-α agents such as etanercept, infliximab, and adalimumab are used in refractory cases. SS is usually responsive to oral corticosteroids, and the above-mentioned immunosuppressants should be considered in resistant or highly relapsing cases.

Ciclosporin use during pregnancy

Ciclosporin (cyclosporine) is an immunosuppressive drug first approved for use in organ transplantation to prevent rejection. Ciclosporin is also known to be used for the treatment of psoriasis, rheumatoid arthritis, systemic lupus erythematosus and inflammatory bowel disease, among other indications. While it is recommended that all medications that are not absolutely necessary should be avoided during pregnancy, this may not be an option for many women whose quality of life is significantly impacted without treatment, or for those who must continue immunosuppressive therapy to avoid organ rejection. The purpose of this review is to provide a comprehensive report from the literature of ciclosporin exposure during pregnancy. PubMed, MEDLINE and the Cochrane Database of Systematic Reviews were searched for English-language articles published from 1970 to 2012 that included reports of pregnant women treated at any time during pregnancy with ciclosporin. On an initial search, it was evident that much of the available information is limited to pregnancy after transplant, which suggests that ciclosporin use during pregnancy appears to be associated with premature delivery and low birthweight infants. Comorbidities such as hypertension, pre-eclampsia and gestational diabetes mellitus are also reported at higher incidences than the general population. Medical literature concerning women with autoimmune disorders exposed to ciclosporin during pregnancy are currently limited to case reports and registry data, and, as such, it is difficult to determine if any risks associated with ciclosporin therapy during pregnancy are due to exposure to the drug alone or to pre-existing maternal comorbidities. The literature suggests that ciclosporin therapy during pregnancy should be carefully considered by the treating physician, but may be a safe alternative for patients with autoimmune disease refractory to conventional treatment. Continued monitoring of this patient population remains a key component to understanding the risk factors associated with ciclosporin exposure during pregnancy.

All that is red is not cellulitis. Pyoderma gangrenosum

A 60-year-old patient presented with progressive worsening, non-healing ulcer on her shin with surrounding erythema following a minor trauma and was treated with several antibiotics for presumed cellulitis with no improvement. A skin biopsy eventually suggested pyoderma gangrenosum and a colonic biopsy showed an underlying ulcerative colitis.

The F-BAR protein PSTPIP1 controls extracellular matrix degradation and filopodia formation in macrophages

PSTPIP1 is a cytoskeletal adaptor and F-BAR protein that has been implicated in autoinflammatory disease, most notably in the PAPA syndrome: pyogenic sterile arthritis, pyoderma gangrenosum, and acne. However, the mechanism by which PSTPIP1 regulates the actin cytoskeleton and contributes to disease pathogenesis remains elusive. Here, we show that endogenous PSTPIP1 negatively regulates macrophage podosome organization and matrix degradation. We identify a novel PSTPIP1-R405C mutation in a patient presenting with aggressive pyoderma gangrenosum. Identification of this mutation reveals that PSTPIP1 regulates the balance of podosomes and filopodia in macrophages. The PSTPIP1-R405C mutation is in the SRC homology 3 (SH3) domain and impairs Wiskott-Aldrich syndrome protein (WASP) binding, but it does not affect interaction with protein-tyrosine phosphatase (PTP)-PEST. Accordingly, WASP inhibition reverses the elevated F-actin content, filopodia formation, and matrix degradation induced by PSTPIP1-R405C. Our results uncover a novel role for PSTPIP1 and WASP in orchestrating different types of actin-based protrusions. Our findings implicate the cytoskeletal regulatory functions of PSTPIP1 in the pathogenesis of pyoderma gangrenosum and suggest that the cytoskeleton is a rational target for therapeutic intervention in autoinflammatory disease.