Immunohistochemical characterization of inflammatory cells and immunologic activation markers in muscle and nerve biopsy specimens from patients with systemic polyarteritis nodosa

Polyarteritis Nodosa: Old Disease, New Etiologies

Polyarteritis nodosa (PAN), also known as panarteritis nodosa, represents a form of necrotizing vasculitis that predominantly affects medium-sized vessels, although it is not restricted to them and can also involve smaller vessels. The clinical presentation is heterogeneous and characterized by a significant number of patients exhibiting general symptoms, including asthenia, fever, and unintended weight loss. Although PAN can involve virtually any organ, it preferentially affects the skin, nervous system, and the gastrointestinal tract. Orchitis is a rare but specific manifestation of PAN. The absence of granulomas, glomerulonephritis, and anti-neutrophil cytoplasmic antibodies serves to distinguish PAN from other types of vasculitis. Major complications consist of hemorrhagic and thrombotic events occurring in mesenteric, cardiac, cerebral, and renal systems. Historically, PAN was frequently linked to hepatitis B virus (HBV) infection, but this association has dramatically changed in recent years due to declining HBV prevalence. Current epidemiological research often identifies a connection between PAN and genetic syndromes as well as neoplasia. This article provides a comprehensive review of PAN, specifically focusing on the progression of its clinical manifestations over time.

Autoimmune Heart Disease: A Comprehensive Summary for Forensic Practice

Autoimmune heart disease is a non-random condition characterised by immune system-mediated aggression against cardiac tissue. Cardiac changes often exhibit nonspecific features and, if unrecognised, can result in fatal outcomes even among seemingly healthy young individuals. In the absence of reliable medical history, the primary challenge lies in differentiating between the various cardiopathies. Numerous immunohistochemical and genetic studies have endeavoured to characterise distinct types of cardiopathies, facilitating their differentiation during autopsy examinations. However, the presence of a standardised protocol that forensic pathologists can employ to guide their investigations would be beneficial. Hence, this summary aims to present the spectrum of autoimmune cardiopathies, including emerging insights such as SARS-CoV-2-induced cardiopathies, and proposes the utilisation of practical tools, such as blood markers, to aid forensic pathologists in their routine practice.

Endovascular Biopsy of Vertebrobasilar Aneurysm in Patient With Polyarteritis Nodosa

Background and Purpose: The management of unruptured intracranial aneurysms remains controversial. The decisions to treat are heavily informed by estimated risk of bleeding. However, these estimates are imprecise, and better methods for stratifying the risk or tailoring treatment strategy are badly needed. Here, we demonstrate an initial proof-of-principle concept for endovascular biopsy to identify the key molecular pathways and gene expression changes associated with aneurysm formation. We couple this technique with single cell RNA sequencing (scRNAseq) to develop a roadmap of the pathogenic changes of a dolichoectatic vertebrobasilar aneurysm in a patient with polyarteritis nodosa.

Methods: Endovascular biopsy and fluorescence activated cell sorting was used to isolate the viable endothelial cells (ECs) using the established techniques. A single cell RNA sequencing (scRNAseq) was then performed on 24 aneurysmal ECs and 23 patient-matched non-aneurysmal ECs. An integrated panel of bioinformatic tools was applied to determine the differential gene expression, enriched signaling pathways, and cell subpopulations hypothesized to drive disease pathogenesis.

Results: We identify a subset of 7 (29%) aneurysm-specific ECs with a distinct gene expression signature not found in the patient-matched control ECs. A gene set enrichment analysis identified these ECs to have increased the expression of genes regulating the leukocyte-endothelial cell adhesion, major histocompatibility complex (MHC) class I, T cell receptor recycling, tumor necrosis factor alpha (TNFα) response, and interferon gamma signaling. A histopathologic analysis of a different intracranial aneurysm that was later resected yielded a diagnosis of polyarteritis nodosa and positive staining for TNFα.

Conclusions: We demonstrate feasibility of applying scRNAseq to the endovascular biopsy samples and identify a subpopulation of ECs associated with cerebral aneurysm in polyarteritis nodosa. Endovascular biopsy may be a safe method for deriving insight into the disease pathogenesis and tailoring the personalized treatment approaches to intracranial aneurysms.

Hypertrophic pachymeningitis in polyarteritis nodosa: a case-based review

Hypertrophic pachymeningitis (HP) is a rare neurological disorder with focal or diffuse thickening of the dura mater, which usually causes headache, cranial neuropathies, seizures, and motor or sensory impairments. The development of HP is attributed to an immune-mediated mechanism, and some autoimmune diseases have been implicated in the development of HP. Herein, we describe the case of a 73-year-old woman with persistent headache ascribable to HP, which developed approximately 3 years after a diagnosis of polyarteritis nodosa (PAN). She was treated with high-dose corticosteroid and cyclophosphamide that resulted in immediate disappearance of headache and improved radiological findings of thickened dura mater. In addition, she was subsequently administered methotrexate, ultimately resulting in maintenance of remission and regular reduction of prednisolone. In our review of published English articles, only two cases of HP in patients with PAN have been reported to date, suggesting that HP is a rare complication in PAN. However, it should be recognized that HP may develop as a neurological involvement related to PAN.

The ratio of CD163-positive macrophages to Iba1-positive macrophages is low in the intima in the early stage of cutaneous arteritis

The etiology of polyarteritis nodosa (PAN) and localized PAN, including cutaneous arteritis (CA), remains unknown; however, initial endothelial damage has been implicated. The intima of the vasculitis lesions is predominantly infiltrated by innate-like bystander-activated CD8 T cells, in addition to the macrophages. Macrophages are among the major inflammatory cells involved in innate immunity and are classified into M1 and M2 subtypes. M1-type macrophages kill pathogens and cause inflammation, while M2-type macrophages promote the repair of tissues. Macrophage subtypes infiltrating in PAN and localized PAN vasculitis lesions have not yet been investigated. Innate immune response to a triggering factor on the endothelial cell surface may initiate CA pathogenesis. Thus, many M1-type macrophages may infiltrate in the intima during early CA. We assessed this hypothesis by immunohistochemical observation of macrophage phenotypes and polarization. Twenty-seven skin biopsy specimens from patients with CA were retrieved. Based on histology, we classified CA into four phases. The phenotypes of infiltrating macrophages in CA were evaluated by immunohistochemistry using antibodies against Iba-1, a pan-macrophage marker, and CD163, an M2-type macrophage marker. Our results showed that the ratio of CD163-positive M2-type macrophages to Iba1-positive macrophages was lower in the intima in the early stage of CA than in the later stage. In the media to adventitia, there was no significant difference in the ratios between these stages. These findings indicate that innate immunity is involved in the intima in the early stage of CA, suggesting that a trigger for CA might exist in endothelial cells.

Coexistence of Polyarteritis Nodosa of the Vulva and Retina in a Behçet's Disease Patient: A Case Report

Polyarteritis nodosa (PAN) is a multisystem disease that may affect the vessels of multiple organ systems. It has clinical variants including single-organ disease and cutaneous-only PAN. To our knowledge, this is a unique case report describing the coexistence of PAN of the vulva and retina in a Behçet's disease (BD) patient.  We report a case of a 31-year-old Lebanese woman with painful genital ulcers and multiple oral aphthae associated with arthralgia, light flashes, blurry vision, and photosensitivity. There were well-defined, punched-out erosions over the buccal and gingival mucosa; specifically, multiple punched-out, deep ulcers with unremarkable borders and black eschar involving two-thirds of both labia majora and minora sparing the clitoris with bilateral inguinal lymphadenopathy. Dilated fundus examination showed a few cotton wool spots and intraretinal hemorrhage. Fundus fluorescein angiography showed multiple arteriolar infarctions involving the macula in both eyes, more so in the right eye. Vulvar biopsy was consistent with PAN due to the involvement of a medium-sized subcutaneous artery and showed neutrophilic infiltration of its wall. Stain for elastic lamina showed medium-sized subcutaneous artery involvement. After ruling out infectious aetiologies, she was managed by intravenous pulse methylprednisolone 1,000 mg for three days, followed by oral prednisolone 50 mg with a slow taper, oral colchicine 0.5 mg twice daily, and adalimumab 40 mg once every two weeks to stop the progression of the ocular insult and genital mutilation. There was significant improvement of the ulcer with no new cutaneous or systemic manifestations. This case report highlights the importance of considering PAN-like lesions in cases of Behçet's disease. We emphasized the addition of cutaneous PAN as one of the cutaneous manifestations of BD.

CD8+ T Cells in GCA and GPA: Bystanders or Active Contributors?

Vasculitis refers to inflammation of blood vessels and can cause a variety of serious complications depending on which vessels are affected. Two different forms of vasculitis are Giant Cell Arteritis (GCA) and Granulomatosis with Polyangiitis (GPA). GCA is the most common form of vasculitis in adults affecting the large arteries and can lead to visual impairment and development of aneurysms. GPA affects small- and medium-sized blood vessels predominantly in the lungs and kidneys resulting in organ failure. Both diseases can potentially be fatal. Although the pathogenesis of GCA and GPA are incompletely understood, a prominent role for CD4+ T cells has been implicated in both diseases. More recently, the role of CD8+ T cells has gained renewed interest. CD8+ T cells are important players in the adaptive immune response against intracellular microorganisms. After a general introduction on the different forms of vasculitis and their association with infections and CD8+ T cells, we review the current knowledge on CD8+ T-cell involvement in the immunopathogenesis of GCA and GPA focusing on phenotypic and functional features of circulating and lesional CD8+ T cells. Furthermore, we discuss to which extent aging is associated with CD8+ T-cell phenotype and function in GCA and GPA.

Clinical Approach to Diagnosis and Therapy of Polyarteritis Nodosa

PURPOSE OF THE REVIEW

Polyarteritis nodosa is a rare disease characterized by the necrotizing inflammation of medium-sized arteries. Different etiopathogenetic and clinical variants of the disease have been recognized over the past decades. In the present paper, we review the clinical features, diagnosis, and treatment of the different subtypes of the disease.

RECENT FINDINGS

The diagnosis of polyarteritis nodosa is primarily based on clinical findings, imaging, and histopathological investigations. Microbiological and genetic investigations complement the diagnostic work-up. Idiopathic and hereditary variants of polyarteritis nodosa are treated with immunomodulatory medications such as glucocorticoids, conventional immunomodulatory drugs (e.g., cyclophosphamide) and biologic agents (e.g., tumor necrosis factor inhibitors, interleukin 6 inhibitor), while hepatitis B virus-associated polyarteritis nodosa primarily requires antiviral therapy combined with plasma exchange. PAN is a disease with heterogeneous presentations, severity, and therapeutic approaches. The overall prognosis of this disease is improving, mainly due to early diagnosis and more effective treatments. Treatment choices are guided mainly by the disease subtype and severity. In this review, we have presented the current knowledge on PAN clinical variants, their classification, diagnosis, and treatment approaches.

[Update: polyarteritis nodosa]

Polyarteritis nodosa (PAN) is a necrotizing arteritis of medium-sized vessels, which is often fatal if untreated. It frequently affects the skin (nodules and ulcers), the peripheral nervous system (mononeuritis multiplex) and the visceral vessels (stenoses and microaneurysms). The complex diagnostic work-up requires discriminating PAN from infectious, malignant, drug-induced and other inflammatory conditions. It can be subclassified into further variants (idiopathic, associated with hepatitis B, associated with hereditary inflammatory diseases or isolated cutaneous disease). While idiopathic and hereditary inflammatory variants require immunosuppressive treatment, the hepatitis B-associated variant is treated with virustatic agents and plasmapheresis. The isolated cutaneous variant has a good prognosis and rarely requires highly potent immunosuppressives.

Polyarteritis Nodosa in a Cat with Involvement of the Central and Peripheral Nervous Systems

An 18-month-old neutered male domestic shorthair cat was referred with a history of pyrexia, polyuria and polydypsia, and transient episodes of bilateral hindlimb paralysis. Cardiac evaluation revealed severe systemic hypertension and severe concentric hypertrophy of the left ventricle. One month later the cat had a new episode of hindlimb paralysis with recurrent seizures, and died in status epilepticus. At necropsy examination, the coronary arteries, arcuate renal arteries and common iliac arteries showed marked thickening with nodules segmentally located along the vessels and consequent narrowing of the lumina. Histologically, acute and chronic inflammatory infiltration of the vascular walls was associated with necrosis of the muscular layer. Lesions were consistent with polyarteritis nodosa and involved the small, medium and large arteries of the heart, kidneys, small and large intestine, mesentery, liver and thyroid. Multifocal meningeal vasculitis associated with focal infarction of the frontal lobe and necrotizing vascular polyneuropathy were detected. Involvement of the central and peripheral nervous systems in polyarteritis nodosa is a novel finding in cats.

Systemic Necrotizing Vasculitis in Sheep Is Associated With Ovine Herpesvirus 2

Ovine herpesvirus 2 (OvHV-2) is one of the gammaherpesviruses in the genus Macavirus that can cause malignant catarrhal fever (MCF) in ungulates. Sheep are the adapted host for OvHV-2 and it is generally assumed that infection is not associated with disease in this species. However, cases of "polyarteritis nodosa" or idiopathic systemic necrotizing vasculitis reported in sheep are similar to vascular lesions in clinically susceptible species with MCF. Using a recently developed in situ hybridization (ISH) method, we were able to identify OvHV-2 nucleic acids within lesions and correlate the viral distribution with systemic necrotizing vasculitis in 9 sheep, including both naturally and experimentally OvHV-2-infected animals. ISH, combined with polymerase chain reaction and histology, identify OvHV-2 as the likely agent responsible for sporadic, MCF-like vascular disease in sheep.

Pathogenesis of giant-cell arteritis: how targeted therapies are influencing our understanding of the mechanisms involved

GCA is a chronic granulomatous vasculitis that affects large- and medium-sized vessels. Both the innate and the adaptive immune system are thought to play an important role in the initial events of the pathogenesis of GCA. Amplification cascades are involved in the subsequent development and progression of the disease, resulting in vascular inflammation, remodelling and occlusion. The development of large-vessel vasculitis in genetically modified mice has provided some evidence regarding potential mechanisms that lead to vascular inflammation. However, the participation of specific mechanistic pathways in GCA has not been fully established because of the paucity and limitations of functional models. Treatment of GCA is evolving, and novel therapies are being incorporated into the GCA treatment landscape. In addition, to improve the management of GCA, targeted therapies are providing functional proof of concept of the relevance of particular pathogenic mechanisms in the development of GCA and in sustaining vascular inflammation.

In vasculitis of small muscular arteries, activation of vessel-infiltrating CD8 T cells seems to be antigen-independent

The etiology of polyarteritis nodosa (PAN) and localized PAN is still unknown, although a T cell-mediated immune mechanism has been considered. CD8 T cells participate not only in the antigen-dependent adaptive immune system, but also in the antigen-independent innate immune system. Non-antigen-activated CD8 T cells express a unique phenotype: granzyme B (GrB) positive /CD25 negative /programmed death-1 (PD-1) negative. The aims of this study were to assess the participation of T cells, especially innate CD8 T cells, in the development of vasculitis. Twenty-eight consecutive cases of skin biopsy specimens with cutaneous vasculitis of small muscular arteries (CVSMA) were retrieved. The series comprises of 21 cases of cutaneous arteritis, three cases of PAN, and four cases of rheumatoid vasculitis. Cases of antineutrophil cytoplasmic antibody-associated vasculitis were excluded. The phenotypes of infiltrating lymphocytes in vasculitis lesions were evaluated by immunohistochemistry. In most cases of CVSMA, the number of CD8 T cells infiltrating the intima was higher than that of CD4 T cells, and significant numbers of GrB-positive cells, which represent activated CD8 T cells, were observed. However, GrB/CD25-double-positive cells, which correspond to antigen-activated T cells, were very few in a small number of cases. Cells positive for PD-1, which is also expressed on antigen-activated CD8 T cells, were not detected. We conclude that a T cell-mediated immune mechanism, involving cytotoxic CD8 T cells, may play a role in the development of CVSMA. Low expression of CD25 in activated CD8 T cells suggests that activation was antigen-independent.

Imbalanced expression of dysfunctional regulatory T cells and T-helper cells relates to immunopathogenesis in polyarteritis nodosa

OBJECTIVES

We investigated the characteristics of circulating T-helper (Th) cells and CD4⁺ regulatory T cells (Tregs) in polyarteritis nodosa (PAN).

METHODS

Peripheral blood samples were obtained from 14 patients with PAN. Nine patients having granulomatosis with polyangiitis (GPA) and 11 healthy individuals (HC) were enrolled as controls. Th cells and Tregs were analyzed by flow cytometry. Suppression assay of Tregs was simultaneously performed by evaluating the proliferation of conventional CD4⁺ T cells cocultured with Tregs.

RESULTS

The frequencies of Th cells were significantly higher in PAN than in HC. In comparison with GPA, the expression of Th1 cells was higher but that of Th17 cells was lower. Additionally, significant increase in Tregs was observed in PAN, which was correlated with the expression of Th1 cells; however, defects in suppressive ability and CTLA-4 expression were observed. The Th1-cell frequency was significantly decreased after immunosuppressive therapy in PAN; however, there were no improvements in other phenotypes or in Treg function.

CONCLUSION

T-helper cell expansion and Treg dysfunction are thought to be associated with the pathogenesis of PAN. Th1 cells show a response to immunosuppressive therapy; however, the persistent immune abnormalities may interfere with complete recovery in patients with PAN.

Trypanosoma cruzi Causes Paralyzing Systemic Necrotizing Vasculitis Driven by Pathogen-Specific Type I Immunity in Mice

Infectious agents are often considered potential triggers of chronic inflammatory disease, including autoimmunity; however, direct evidence is usually lacking. Here we show that following control of acute infection of mice with the myotropic Colombiana strain of Trypanosoma cruzi, parasites persisted in tissue at low levels associated with development of systemic necrotizing vasculitis. Lesions occurred in many but not all organs and tissues, with skeletal muscle arteries being the most severely affected, and were associated with myositis, atrophy, paresis/paralysis, and death. Histopathology showed fibrinoid vascular necrosis, rare amastigote nests within skeletal muscle myocytes, and massive leukocyte infiltrates composed mainly of inflammatory monocytes, F4/80(+)macrophages, and T. cruzi tetramer-specific CD8(+) T lymphocytes capable of producing gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) but not interleukin-17 (IL-17). T. cruzi-specific IgG was detected in sera from infected mice, but antibody deposits and neutrophilic inflammation were not features of the lesions. Thus,T. cruzi infection of mice may be a specific infectious trigger of paralyzing systemic necrotizing vasculitis most severely affecting skeletal muscle, driven by pathogen-specific type I immune responses.

Polyarteritis nodosa: A contemporary overview

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis predominantly targeting medium-sized arteries. PAN is a rare form of vasculitis, and the precise frequency of this disease is difficult to determine. The major environmental factor associated with PAN is HBV infection. The pathogenesis of "idiopathic PAN" remains enigmatic, although the clinical responses to immunosuppressive therapy support the concept that immunological mechanisms play an active pathogenic role. The spectrum of disease ranges from involving a single organ to polyvisceral failure. Any organ might be affected; however, for reasons that are not understood, PAN does not affect the lungs. In addition to the systemic idiopathic form, called "idiopathic generalized PAN," there are 2 clinical variants of this disease: "cutaneous PAN" and "hepatitis B virus (HBV)-associated PAN". Diagnosis requires the integration of clinical, angiographic, and biopsy findings. The overall prognosis of this disease has been improved in recent decades, primarily reflecting early diagnosis and more effective treatments. Idiopathic generalized PAN should be treated with a combination of glucocorticoids and cyclophosphamide. The treatment of HBV-associated PAN involves a different approach, centered on the use of an antiviral agent to control the infection. The therapy for cutaneous PAN requires a less aggressive approach based on the administration of non-steroidal anti-inflammatory drugs over short periods of time.

A case of refractory polyarteritis nodosa successfully treated with rituximab

A 59-year-old man who presented with continuous fever, livedo reticularis, and left leg ischemia with multiple tibial artery stenosis and renal artery aneurysm, as demonstrated by arteriography, was diagnosed with polyarteritis nodosa (PAN) 6 years ago. Although he frequently relapsed in spite of intensive immunosuppressive therapies, the disease activity of PAN was controlled with repeated rituximab (RTX) therapies and steroid doses were tapered safely. Peripheral CD19⁺ B-cells disappeared soon after the 1st administration of RTX. Although CD19⁺ B-cells remained absent, 3.1% of CD3⁺CD20⁺ T-cells were observed in the peripheral blood prior to the 2nd administration of RTX. Recent studies have suggested the pathogenic role of CD3⁺CD20⁺ T-cells in autoimmune diseases in the context of RTX therapy; therefore, their roles in the pathogenesis of PAN also need to be considered.

Diagnosis and classification of polyarteritis nodosa

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis preferentially targeting medium-sized arteries and not associated with glomerulonephritis or small vessel involvement. Anti-neutrophil cytoplasmic antibodies are typically negative. PAN may be triggered by viral infections, particularly hepatitis B virus, but remains idiopathic in most cases. Clinical manifestations of PAN are multisystemic. Peripheral nerve and skin are the most frequently affected tissues. Involvement of the gastrointestinal tract, kidneys, heart, and central nervous system is associated with higher mortality. Laboratory abnormalities reveal a prominent acute phase response but are non-specific. Histologic confirmation of vasculitis in medium sized arteries is desirable and biopsies must be obtained from symptomatic organs if feasible. Skin or muscle and nerve are preferred because of higher diagnostic yield and safety. If biopsies are negative or cannot be obtained, visceral angiography, may reveal multiple micro-aneurysms supporting the diagnosis of PAN. Current treatment policy includes high-dose corticosteroids, which are combined with immunosuppressive agents when critical organ involvement or life-threatening complications occur. IV pulse cyclophosphamide in the remission induction phase, later switched to a safer immunosuppressant for remission maintenance is a frequently used therapeutic approach. A recent consensus algorithm for the classification of PAN has attempted to overcome some of the caveats of the 1990 American College of Rheumatology (ACR) classification criteria which have proven to be unsatisfactory, and has also confirmed the low prevalence of PAN compared to other systemic necrotizing vasculitides. European league against rheumatic diseases (EULAR)/ACR endorsed international cooperation to establish new diagnostic/classification criteria is currently under way.

Vasculitic neuropathy

Vasculitis is a primary phenomenon in autoimmune diseases such as polyarteritis nodosa, Wegener's granulomatosis, Churg-Strauss syndrome, microscopic polyangiitis, and essential mixed cryoglobulinemia. As a secondary feature vasculitis may complicate, for example, connective tissue diseases, infections, malignancies, and diabetes. Vasculitic neuropathy is a consequence of destruction of the vessel wall and occlusion of the vessel lumen of small epineurial arteries. Sometimes patients present with nonsystemic vasculitic neuropathy, i.e., vasculitis limited to peripheral nerves and muscles with no evidence of further systemic involvement. Treatment with corticosteroids, sometimes in combination with other immunosuppressants, is required to control the inflammatory process and prevent further ischemic nerve damage.

Isolated necrotizing arteritis (localized polyarteritis nodosa): examination of the histological process and disease entity based on the histological classification of stage and histological differences from polyarteritis nodosa

INTRODUCTION

Although isolated necrotizing arteritis (INA) has been thought to be an isolated form of polyarteritis nodosa (PAN), a detailed histological comparison between INA and PAN has not been performed. Therefore, we examined the disease entity of INA based on the histological comparison of both diseases. In addition, a histological classification of INA, in which the histological process of INA is included, was described.

METHODS

A histological study, including CD3, CD20, and CD68 immunostains, was performed in seven operated patients with INA. Five untreated patients with PAN were also examined.

RESULTS

In INA, arteritis with fibrinoid necrosis occurred in small and medium-sized arteries in a single organ. INA was divided histologically into acute (five cases) and healed stage (two cases). Endothelial injury and medial degeneration, followed by fibrinoid necrosis, occurred in the acute stage, and regression of fibrinoid necrosis and fibrosis were present in the healed stage. Infiltration of predominant T lymphocytes and macrophages was also observed in the affected arteries. Histological comparison between INA and PAN led to the finding that the extension of fibrinoid necrosis in the entire arterial wall, which indicates severe wall destruction, intense proliferation of fibroblasts and aneurysm formation occurred in PAN alone.

CONCLUSIONS

We demonstrated some histological differences between INA and PAN. Based on the histological similarities and differences between INA and PAN, it was concluded that INA shall be classified as a mildly wall destructive form of PAN-type arteritis located in a single organ.

Cryofibrinogenemia associated with polyarteritis nodosa

We report the case of a 77-year-old woman with biopsy-confirmed polyarteritis nodosa (PAN) associated with cryofibrinogenemia presenting with polyarthralgia and digital gangrene induced by cold exposure. The clinical manifestations and parameters measured by laboratory markers including cryofibrinogen responded well to corticosteroid therapy. To our knowledge, the case of the combination of PAN and cryofibrinogenemia has not been reported. Our case indicates that cryofibrinogenemia might be associated with PAN. The PAN patients with cold-induced symptoms should be screened for cryofibrinogen.

Polyarteritis nodosa in a cynomolgus macaque (Macaca fascicularis)

Polyarteritis nodosa (PAN) is an idiopathic necrotizing vasculitis affecting small- to medium-sized arteries. The disease is well recognized in humans, and PAN-like syndromes have been described in a number of other species. This report describes a case of PAN in a 6-year-old male cynomolgus macaque. The animal had necrotizing arteritis affecting vessels in the kidney, small intestine, colon, heart, spleen, mesentery, urinary bladder, and pancreas. The lesions were segmental in distribution and of varying severity and stage of development. A transmural mixed inflammatory cell infiltrate was present, often accompanied by fibrinoid necrosis of the tunica media and loss of the internal elastic lamina. Immunohistochemical staining showed that many of the infiltrating cells were T lymphocytes and histiocytes, suggesting a cell-mediated component to the pathogenesis.

The appearance of S-100 protein-positive dendritic cells and the distribution of lymphocyte subsets in idiopathic nonspecific interstitial pneumonia

Idiopathic interstitial pneumonia (IIP) is a progressive interstitial lung disease of unknown etiology. We investigated dendritic cells in idiopathic nonspecific interstitial pneumonia (NSIP) immunohistochemically, using anti-S-100 protein antibody and anti-HLA-DR antibody and also evaluated the relationship between the distribution of S-100 protein-positive dendritic cells (S- 100 DCs) and the lymphocytic subsets in the lung tissue of NSIP. Fifteen patients with the pathological diagnosis of idiopathic NSIP and six patients with usual interstitial pneumonia (UIP) were recruited into this study. Many S-100 DCs were observed in all the cases of idiopathic NSIP but S-100 DCs were not recognized in UIP cases invariably. In the mirror section method, most S-100 DCs showed a positive reaction of anti-HLA-DR antibody but a negative reaction for anti-CD1a antibody. CD8 and CD4 positive lymphocytes were infiltrated diffusely around S-100 DCs. It was demonstrated that the infiltration of CD8 positive lymphocytes predominated in the fibrosing areas and lymphoid follicles around S-100 DCs more so than CD4 positive lymphocytes.We speculate that the pathogenesis of NSIP is different from UIP and that DC and T cell-mediated immune mechanisms may play a role in the development and perpetuation of NSIP.

Tissue and Serum Angiogenic Activity Is Associated With Low Prevalence of Ischemic Complications in Patients With Giant-Cell Arteritis

Background— Vascular inflammatory lesions from patients with giant-cell arteritis show a remarkable amount of neovascularization, but its clinical implications have never been investigated.

Methods and Results— To assess the clinical relevance of neovascularization in giant-cell arteritis, angiogenesis was measured in temporal artery sections from 31 patients with biopsy-proven giant-cell arteritis by staining endothelial cells with Ulex europaeus lectin. Angiogenesis was highly variable among these patients. Patients without ischemic complications had higher tissue angiogenesis scores than patients with ischemic events (5.69±0.6 versus 2.91±0.6, P =0.003). Angiogenesis was also more prominent in patients with a strong acute phase response (score: 5.31±0.6) compared with those with a weak systemic inflammatory reaction (2.30±0.44; P =0.0007). Serum angiogenic activity was studied in an additional series of 38 biopsy-proven patients. Sera from patients without ischemic events tended to be more active in stimulating human umbilical vein endothelial cell growth (optical density ×1000, 270±15 versus 192±14, P =0.065) and differentiation into capillary-like structures (107±5 versus 84±8 relative units, P =0.0058) than patients with ischemic complications. Sera from patients without ischemic events had more in vivo full angiogenic activity tested in the chick chorioallantoic membrane than sera from patients with ischemic complications.

Conclusion— Inflammation-induced angiogenic activity may play a compensatory role for ischemia in patients with giant-cell arteritis.

Polyarteritis nodosa presenting as polymyositis

BACKGROUND

Skeletal muscle involvement has been well documented in patients with polyarteritis nodosa (PAN), and symptoms referable to skeletal muscle are not uncommon. However, polymyositis as a mode of presentation of PAN is uncommon. This unusual presentation of PAN has been reported only once previously in the English literature.

OBJECTIVE

This study describes a patient who had diffuse weakness, myalgias, and markedly elevated serum creatinine phosphokinase, mimicking polymyositis. The literature dealing with the clinical aspects of muscle involvement in PAN is reviewed.

RESULTS

A 24-year-old man was admitted to the hospital with a 1-month history of fever, myalgia, and muscle weakness. Necrotizing vasculitis was shown on subsequent muscle biopsy, consistent with PAN. Literature review indicated that muscle involvement is common in PAN, as has been shown by the frequency of muscular symptoms and by histologic evidence obtained from both clinical and autopsy studies. Nineteen percent of patients with PAN had documented myopathy, and autopsy series have shown skeletal muscle involvement in 30% to 48% of cases. However, polymyositis as a mode of presentation of PAN is rare. We found only 1 other patient with PAN who had elevated creatinine phosphokinase and diffuse myopathy suggestive of polymyositis.

CONCLUSIONS

PAN should be suspected in cases of focal or diffuse myopathy, especially in the context of a systemic disease. Biopsy of symptomatic muscles or EMG-directed biopsies can be helpful in establishing a diagnosis of PAN to allow the physician to provide early treatment.

Polyarteritis nodosa and microscopic polyangiitis: etiologic and diagnostic considerations

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis of medium-sized vessels with clinical manifestations resulting from ischemia and infarction of affected tissues and organs. Although the cause of most cases of PAN and the related disorder microscopic polyangiitis (MPA) remains largely unknown, there has been significant progress in understanding the pathogenesis of vascular inflammation. The diagnostic approach to PAN and MPA should be individualized and based on specific organ involvement. Because no test or clinical finding reliably indicates the presence or absence of PAN or MPA, diagnosis requires integration of clinical findings, angiography, and biopsy data.

Tissue targeting and disease patterns in systemic vasculitis

The systemic vasculitides include a group of diseases with highly heterogeneous organ distribution and disease expression patterns. The mechanisms mediating tissue targeting in systemic vasculitis are largely unknown. Mechanical forces may contribute to the distribution of lesions in immune complex-mediated vasculitis. The site at which the antigen is encountered may be crucial in determining the location of inflammatory infiltrates in some vasculitides. Co-existence of different immunopathogenic mechanisms with variable dominance may generate diversity in disease presentation patterns. Heterogeneous and incompletely understood triggering mechanisms attract inflammatory cells to the site of interest through sophisticated molecular mechanisms: interplay between leukocyte receptors and endothelial ligands, and interactions between chemokines and chemokine receptors. Even with a similar distribution of lesions, patients with vasculitis may display highly variable clinical manifestations. Variations in genes involved in immune response might determine the severity of disease, the intensity of the systemic inflammatory response, the degree of vessel occlusion and the response to therapy.

Cell death in vasculitic neuropathy

Vasculitic neuropathy shows cluster of differentiation (CD)4+ and CD8+ perivascular infiltrates. CD8+ cells kill the target by different ways. Some mechanisms require the release of granzymes and T-cell restricted intracellular antigen (TIA-1) which induce cell death by apoptosis. A nonsecretory ligand-mediated mechanism has been proposed for apoptosis and requires the interaction of Fas and Fas-ligand. We studied apoptosis by immunohistochemistry and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) in nerve biopsy specimens in 19 cases of vasculitic neuropathy and 8 controls. In vasculitic neuropathy, perivascular mononuclear cells expressed TIA-1, granzyme A, and granzyme B. Regarding the ligand-mediated mechanism, we observed Fas+ and Fas-ligand+ mononuclear cells in an epineurial-perivascular distribution. Cells undergoing apoptosis, as demonstrated by TUNEL, represented mononuclear cells. In vasculitic neuropathy, apoptosis by both a secretory and a nonsecretory mechanism is suspected. However, apoptosis seems to be restricted to inflammatory mononuclear cells, suggesting that it may play a critical role in recovery from vasculitic neuropathy.

Physiologic role of interleukin-1 receptor antagonist

Recent studies have described the spontaneous development of arthritis or vasculitis in IL-1 receptor antagonist (IL-1Ra) knockout mice bred on specific and different genetic backgrounds. The levels of both secreted and intracellular isoforms of IL-1Ra produced in the rheumatoid joint or in the arterial wall may not be adequate to effectively inhibit the excess amounts of locally produced IL-1. Thus, an imbalance between IL-1 and IL-1Ra may predispose to local inflammatory disease in particular tissues in the presence of other as yet unknown genetically influenced factors.

Polyarteritis nodosa, microscopic polyangiitis and Churg-Strauss syndrome

Polyarteritis nodosa (PAN), first described by Küssmaul and Maier, is a well-known form of necrotizing angiitis whose manifestations are weight loss, fever, asthenia, peripheral neuropathy, renal involvement, musculoskeletal and cutaneous manifestations, hypertension, gastrointestinal tract involvement, and cardiac failure. Recently individualized from PAN, microscopic polyangiitis (MPA) is a systemic vasculitis of small-size vessels whose clinical manifestations are very similar to those of PAN, but it is characterized by the presence of rapidly progressive glomerulonephritis (RPGN), which is nearly constant, and pulmonary involvement usually absent in PAN. Churg Strauss syndrome (CSS) is a disorder characterized by hypereosinophilia and systemic vasculitis similar to that of PAN and occurring in individuals with asthma and allergic rhinitis. Considering the etiologies of PAN, primary and secondary vasculitides can also be distinguished because PAN can be the consequence of hepatitis B virus (HBV) infection and sometimes of other etiologic agents. The prognosis of systemic vasculitides has been transformed by corticosteroids that are, except in HBV-related PAN, the basic treatment. Immunosuppressive drugs, especially cyclophophamide, have also contributed to improving the prognosis, but their precise role in the management of these vasculitides is still being elucidated.

Dynamic pattern of endothelial cell adhesion molecule expression in muscle and perineural vessels from patients with classic polyarteritis nodosa

OBJECTIVE

To investigate endothelial cell adhesion molecule expression in vessels from patients with classic polyarteritis nodosa (PAN).

METHODS

Frozen sections of 21 muscle and 16 nerve samples from 30 patients with biopsy-proven PAN and 12 histologically normal muscle and 2 histologically normal nerve samples from 12 controls were studied immunohistochemically, using specific monoclonal antibodies (MAb) that recognize adhesion molecules. Adhesion molecules identified were intercellular adhesion molecule 1 (ICAM-1), ICAM-2, ICAM-3, vascular cell adhesion molecule 1 (VCAM-1), platelet endothelial cell adhesion molecule 1 (PECAM-1), E-selectin, P-selectin, L-selectin, lymphocyte function-associated antigen 1 (LFA-1), and very late activation antigen 4 (VLA-4). Neutrophils were identified with a MAb recognizing neutrophil elastase. Endothelial cells were identified with the lectin ulex europaeus.

RESULTS

In early lesions, expression of PECAM-1, ICAM-1, ICAM-2, and P-selectin was similar to that in control samples, and VCAM-1 and E-selectin were induced in vascular endothelium. In advanced lesions, immunostaining for adhesion molecules diminished or disappeared in luminal endothelium, whereas these molecules were clearly expressed in microvessels within and surrounding inflamed vessels. Staining in endothelia from vessels in a healing stage tended to be negative. A high proportion of infiltrating leukocytes expressed LFA-1 and VLA-4, and only a minority expressed L-selectin. No relationship between the expression pattern of adhesion molecules and clinical features, disease duration, or previous corticosteroid treatment was observed.

CONCLUSION

Endothelial adhesion molecule expression in PAN is a dynamic process that varies according to the histopathologic stage of the vascular lesions. The preferential expression of constitutive and inducible adhesion molecules in microvessels suggests that angiogenesis contributes to the persistence of inflammatory infiltration in PAN.