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A premature female Dirofilaria species, subsequently identified as Dirofilaria repens by its morphological features and mitochondrial 12S ribosomal RNA (12S rRNA) gene sequence, was removed from a subcutaneous nodule of the right temporal region of the head in a Japanese woman 2 years after she noticed swelling of her left calf following an insect sting during a tour to Europe; headache symptoms were noticed a few months later. The sequences of the mitochondrial 12S rRNA and cytochrome c oxidase subunit I genes from the organism were almost identical to those of sequences AM779772 (100% homology, 337/337) and AM749233 (99.8% homology, 536/537) of D. repens isolated from humans in Italy. However, the phylogenetic position of the 18S rRNA-internal transcribed spacer 1-5.8S rRNA region was in the same cluster as that of sequence JX290195 of Dirofilaria sp. “hongkongensis” (96.7% homology, 348/360), which was recently reported from Hong Kong as a novel Dirofilaria species. Information on regional genetic variation in D. repens isolated from animals and humans remains scarce. We report the detailed genetic features of this filaria as a reference isolate from a specific endemic area, to enrich the genetic database of D. repens.

Autoinflammatory diseases (AIDs) characterized by recurrent episodes of localized or systemic inflammation are disorders of the innate immune system. Skin lesions are commonly found in AIDs and cutaneous vasculitis can coexist with AIDs and even present as the most striking feature. This review aims to focus on the frequent cutaneous vasculitis association in three monogenic AIDs including familial Mediterranean fever (FMF), deficiency of adenosine deaminase type 2 (DADA2), and the recently identified adult‐onset VEXAS (vacuoles, E1 enzyme, X‐linked, autoinflammatory, somatic) syndrome. Cutaneous vasculitis in FMF is characterized by: (1) small‐vessel vasculitis similar to IgA vasculitis with palpable purpura but increased intussusception complication and less vascular IgA deposit, and (2) cutaneous arteritis–like vasculitis presenting as subcutaneous nodules most often with higher glomerular involvement. DADA2 has a wide spectrum of clinical presentations ranging from fatal systemic vasculitis with multiple strokes, especially in pediatric patients, to limited cutaneous disease in middle‐aged patients. DADA2 shares similar clinical and histopathological features with polyarteritis nodosa (PAN). As a result, DADA2 is commonly initially misdiagnosed as childhood PAN. Livedo racemosa reveals the most common cutaneous manifestation of cutaneous vasculitis in patients with DADA2. VEXAS syndrome is a life‐threatening disease. A diagnosis of VEXAS syndrome should be strongly considered or could be made in patients with skin lesions characterized by Sweet syndrome–like eruption, livedo racemosa, concomitant relapsing polychondritis, deep venous thrombosis, pulmonary involvement, and progressive hematologic abnormalities such as myelodysplastic syndrome with a unique finding of cytoplasmic vacuoles in myeloid and erythroid precursor cells from bone marrow aspirate smear. As skin involvement is common in AIDs and may present as the most frequent manifestation, especially in DADA2 (70% to 90%) and VEXAS syndrome (83% to 91%), dermatologists play a crucial role in contributing to the early diagnosis of these AIDs with early initiation of the appropriate therapy to avoid progressing fatal outcomes. [ABSTRACT FROM AUTHOR]

Objectives: We conducted this study to clarify the progress of cutaneous arteritis. Methods: We examined 21 cases of cutaneous arteritis that were diagnosed at our hospital between 2005 and 2020. The male‐to‐female ratio was 1:6 with a mean age of 52.2 years. Results: The lower legs were involved in all cases, and the upper extremities or trunk was also involved in some cases. Cutaneous manifestations presented as indurated erythema (n = 15), subcutaneous induration (11), edema (7), livedo (6), and ulcer (3). In addition, extracutaneous conditions including numbness (10), arthritis (8), fever (2), and myalgia (1) were observed. Laboratory tests showed an increase of inflammatory markers in most cases (14). Histopathological features showed necrotizing vasculitis of small‐sized arteries at the dermo‐subcutaneous junction, and the inflammatory stages of arteritis were histopathologically divided into acute stage (5), subacute stage (5), reparative stage (7), and healed stage (1). The therapies administered were oral prednisolone (11), antiplatelet drug (14), warfarin (1), non‐steroidal anti‐inflammatory drugs (6), biological drug (1), and other drugs (14). There were no cases showing progression to systemic polyarteritis nodosa during follow‐up period. All three patients with ulceration complained of numbness, and one was revealed to have mononeuropathy multiplex. They were treated with low‐dose oral prednisolone. Three ulceration cases were histopathologically classified into the acute and subacute stages. Conclusions: In conclusion, all 21 patients followed a chronic course with recurrent skin lesions without systemic complications. Cases with ulceration seem to reveal neurological symptoms and need systemic steroid treatment. We conducted this study to clarify the progress of cutaneous arteritis. We examined 21 cases of cutaneous arteritis that were diagnosed at our hospital between 2005 and 2020 and all patients followed a chronic course with recurrent skin lesions without systemic complications. [ABSTRACT FROM AUTHOR]

Previous studies have shown that erythema nodosum-like lesions in patients with Behçet's disease show cutaneous vasculitis of either phlebitis or dermal venulitis. To analyse the clinicopathological characteristics of superficial thrombophlebitis as well as cutaneous venulitis in Behçet's disease. We re-evaluated the histopathological features of superficial thrombophlebitis in patients with Behçet's disease. Five patients, one man and four women, developed superficial thrombophlebitis on the lower extremities. Two of the patients had vascular Behçet's disease, both also developed deep vein thrombosis. One patient had intestinal Behçet's disease. In all cases, venulitis in the overlying lower dermis or adjacent subcutis spreading from the main affected subcutaneous thrombophlebitis lesions was observed. Both neutrophilic venulitis (n = 2) and lymphocytic venulitis (n = 3) were observed at the same depth level or upper/lower location of the thrombophlebitis in the same specimens. In addition, concurrent venulitis with fibrin thrombus and fibrinoid necrosis was observed in one case, suggesting that fibrin thrombus affected both venules and muscular veins. By contrast, arteritis or arteriolitis at the same depth level was not observed. Our results showed histopathological features of coexistent thrombophlebitis and venulitis without involvement of either arteries or arterioles in the biopsied specimens of superficial thrombophlebitis. Further studies are necessary to support that those unique histopathological findings are the characteristic features and significant diagnostic indicators of Behçet's disease. [ABSTRACT FROM AUTHOR]

Cutaneous vasculitis can be classified into two types based on the affected vessel size: small vessel vasculitis predominantly affecting dermal venules, and muscular vessel vasculitis as found in cutaneous arteritis predominantly affecting arteries located at the dermal‐subcutaneous junction. We describe two cases with a novel small vessel vasculitis disorder, which exclusively affected arterioles in the mid‐dermis, and show clinical and pathological difference distinct from cutaneous polyarteritis nodosa and cutaneous venulitis. Both patients were male, and presented with painful infiltrative plaques, involving the palms, soles, and thighs without extracutaneous involvement except for fever and arthralgia. Histopathological examination revealed vasculitis in the mid‐dermis characterized by a predominant infiltration of neutrophils with vessel wall fibrinoid necrosis and leukocytoclasia identical to the features of leukocytoclastic vasculitis, except that the affected vessels were arterioles rather than venules. Serological examinations showed normal levels of serum complements, immune complexes, and antineutrophil cytoplasmic antibodies, and vasculitis disorders associated with systemic diseases were excluded in both patients. The patients showed a good response to short‐term treatment with prednisolone up to 30 mg. This novel cutaneous arteriolitis clinicopathologically different from both cutaneous venulitis and cutaneous arteritis appears to be a skin‐limited disorder. [ABSTRACT FROM AUTHOR]

I Dear editor, i Pityriasis lichenoides et varioliformis acuta (PLEVA) is a cutaneous inflammatory disease that presents with infiltrated erythema, papules with collarette scales and haemorrhagic or necrotising crusts on lower extremities [Correction added on 27 April 2020, after first online publication: "acuta" has been added to pityriasis lichenoides et varioliformis in the article title and first paragraph.]. Although it has been known to present features of lymphocytic vasculitis, the key finding of lymphocytic vasculitis characterised by vessel wall fibrinoid necrosis with a predominant infiltrate of lymphocytes has rarely been demonstrated. (HE, x20). c, d) Lymphocytic vasculitis with fibrinoid necrosis of the involved vessel wall and a predominant infiltrate of lymphocytes with the absence of nuclear debris. [Extracted from the article]

Background There is controversy on whether lymphocytic thrombophilic arteritis ( LTA) and macular arteritis ( MA) are a different entity from cutaneous polyarteritis nodosa (C- PAN). Objective To evaluate the controversy on LTA/ MA by examining the morphologic changes during the dynamic inflammatory process. Materials and methods A clinical and histopathological investigation of 46 biopsy specimens from 21 histopathologically proven C- PAN patients at our hospital was performed. Results Most of the biopsy findings revealed arteritis in the subacute and reparative stages. Coexistence of different stages was found in over half of the specimens. Two biopsy specimens consistent with LTA/ MA showed coexisting histologically proven (subacute stage) C- PAN in other lesions. Analyses of the longitudinal sections showed focal and segmental arteritis. Patients overall improved well with compression stockings, anti-inflammatory agents, a prostaglandin analog and antiplatelet agents. Currently, three patients are medication free and only require compression stockings. Conclusion LTA/ MA seems to be part of the spectrum of C- PAN. The vasculitic lesions of C- PAN are segmental and focal, and coexist in different stages. As the chronic stage of C- PAN can be mistaken as LTA/ MA, it is necessary to perform multiple biopsies, serial sections and analyses of longitudinal sections to confirm the main finding of vasculitis. [ABSTRACT FROM AUTHOR]

Key Clinical Message: We reported a patient with systemic lupus erythematosus complicated by livedoid vasculopathy (LV), who responded well to intravenous immunoglobulin and warfarin. Cutaneous lesions of LV resemble those of cutaneous vasculitis. LV should be included in the differential diagnosis of leg ulcerations even in the presence of autoimmune disorders. We reported a patient with systemic lupus erythematosus complicated by livedoid vasculopathy (LV), who responded well to intravenous immunoglobulin and warfarin. Cutaneous lesions of LV resemble those of cutaneous vasculitis. LV should be included in the differential diagnosis of leg ulcerations even in the presence of autoimmune disorders. [ABSTRACT FROM AUTHOR]

Competing Interests: The author declares no conflicts of interest.

Background: The diverse histopathologic spectrum of cutaneous vasculitis in eosinophilic granulomatosis with polyangiitis (EGPA, Churg-Strauss syndrome) has not been well described., Methods: Fifteen skin biopsy specimens from 9 EGPA patients with histopathologically proven necrotizing vasculitis were reviewed clinicopathologically., Results: Among 8 patients with dermal small vessel vasculitis, neutrophilic vasculitis was observed in 2 myeloperoxidase (MPO)-antineutrophil cytoplasmic antibodies (ANCA)-positive patients, whereas the remaining 6 MPO-ANCA-negative patients showed eosinophilic vasculitis in 3 and a mixed infiltrate of neutrophils and eosinophils in another 3 patients. Five patients with muscular vessel vasculitis showed vasculitis at different inflammatory stages in separate or coexisting at the same biopsied skin lesions: acute stage (eosinophilic vasculitis), granulomatous stage (granulomatous vasculitis), and healed stage. Coexistent small vessel and muscular vessel vasculitis was found in 4 patients., Conclusions: The histopathologic spectrum of dermal small vessel vasculitis in EGPA ranges from eosinophilic vasculitis with negative MPO-ANCA at one end to neutrophilic vasculitis with positive MPO-ANCA at the other end. The affected vessels ranging from dermal small vessels to subcutaneous muscular vessels in addition to the MPO-ANCA phenotype may account for the many facets of vasculitis in EGPA.

A case of a 7-year-old girl with microscopic polyangiitis (MPA) with a skin eruption characterized by maculopapular, erythematous and purpuric lesions on the face, elbows, and knees is presented. Anti-neutrophil cytoplasmic autoantibodies (ANCA) with myeloperoxidase specificity (MPO-ANCA) were identified. Chest X-ray and computed tomography scan revealed diffuse infiltrates in both lung fields, suggesting alveolar hemorrhage. Microscopic hematuria was detected but a renal biopsy showed no abnormalities. Histological examination of a skin biopsy from a purpuric papule showed leukocytoclastic vasculitis of the small vessels in the entire dermis. The patient was treated with prednisolone and mizoribine, resulting in an improvement in the skin lesions except for those on the knee.

The presence of an internal elastic lamina and a compact concentric muscular layer are the cardinal histologic clues for distinguishing a small muscular artery from small muscular vein. However, the subcutaneous muscular veins in the lower legs usually have thick muscular layers with the proliferation of concentric intimal elastic fibers, which resembles the internal elastic lamina of an artery. Moreover, vertical biopsy specimens of the muscular veins can reveal a compact concentric muscular layer with a round luminal appearance, which also resembles the muscular layer in an artery. As these 2 histologic features are commonly accepted as crucial clues for identifying small to medium-sized muscular arteries, it seems that many cases that are histopathologically proven to be deep dermal or subcutaneous arteritis-including cases documented in numerous dermatology, rheumatology, and dermatopathology-related journals as cutaneous polyarteritis nodosa in Behçet's disease and relapsing polychondritis or granulomatous arteritis in nodular vasculitis-are actually consistent with the features of phlebitis or thrombophlebitis. Cutaneous polyarteritis nodosa and subcutaneous thrombophlebitis are usually found in the lower legs and may present with the same cutaneous manifestation of widespread tender or painful nodular erythema. This also accounts for the difficulty in clinically and histopathologically distinguishing between these 2 disorders. Nevertheless, it is important to make a distinction between arteritis and phlebitis because misdiagnosing subcutaneous thrombophlebitis as polyarteritis nodosa may lead to overtreatment with high doses of systemic steroids. Although the veins in the lower legs may have a compact concentric smooth muscle pattern with a round lumen and the intimal elastic fiber proliferation mimicking the characteristic features of arteries, the elastic fibers in the muscular layer are distributed between the bundled smooth muscle in veins, whereas the elastic fibers are scantly distributed in the medial muscular layer in arteries. A diagnostic assessment that is based on the amount of the elastic fibers in the muscular vessel wall more reliably distinguishes a vein from an artery than does the presence or absence of the internal elastic lamina or a smooth muscle pattern.

We report a case of common mantle cell lymphoma (MCL) with subcutis infiltration and transformation to blastoid MCL in the overlying dermis. The patient was initially diagnosed as having chronic lymphocytic leukemia and treated with chemotherapy. Eight months after the diagnosis of MCL with bone marrow involvement, subcutaneous nodules developed on the patient's left thigh and forearm. A skin biopsy showed a massive infiltration of neoplastic lymphocytes throughout the dermis and subcutaneous tissue. In the upper dermis, there was a perivascular mixed infiltrate of atypical large lymphoid cells and small-sized cells. In the mid to lower dermis, the infiltrate was dense with a nodular growth pattern and was composed of atypical large lymphoblast-like cells with large nuclei, dispersed chromatin, and numerous mitoses. In the subcutaneous tissue, there was a diffuse infiltration of neoplastic cells with common MCL cytologic features characterized by small- to medium-sized lymphoid cells. Cells in the common and blastoid variants of MCL were immunohistochemically positive for CD20 and cyclin D1 but negative for CD5. Neoplastic lymphocytes from the patient's bone marrow had the typical morphologic features and the immunophenotype of MCL (ie, CD5, CD20, cyclin D1, CD10, and CD23). Other case reports in the medical literature indicate that an MCL with skin invasion tends to have a poor prognosis. Our patient died 3 months after the appearance of skin invasion.

Livedoid vasculopathy has been accepted as a nonvasculitic disorder, but authentic vasculitis in the underlying subcutis can occur in cases of collagen disease and polyarteritis nodosa. We report a case of livedoid vasculopathy with underlying subcutaneous necrotizing venulitis in a 42-year-old carrier of hepatitis B virus. The patient also had a 15-year history of ankylosing spondylitis that was currently in remission. Skin lesions revealed superficial ulceration, purpura, atrophie blanche, and reticulate erythema on the lower extremities, and a skin biopsy showed a minimal dermal perivascular lymphocytic infiltrate with marked fibrin thrombi and fibrin deposits along luminal vessel walls, consistent with features of livedoid vasculopathy. However, necrotizing venulitis characterized by a predominant lymphocytic infiltrate in and around the vessel wall with marked fibrinoid vessel wall necrosis was found in the underlying subcutaneous tissue. A direct immunofluorescence study detected immunoglobulin M and C3 deposits in the papillary dermis. The patient responded well to oral aspirin and a prostaglandin analogue and was well controlled with a compression bandage. Vasculitic lesions in the underlying subcutis may have been overlooked in cases in which livedoid vasculopathy has been considered as a nonvasculitic disorder because our case demonstrates that livedoid vasculopathy can be accompanied by subcutaneous vasculitis.

Morphologic changes including formation of vessel wall fibrinoid necrosis in evolution of cutaneous polyarteritis nodosa (C-PAN) have not been described in detail. Therefore, an investigation of 18 skin biopsy specimens from 14 cases of clinicohistologically proven C-PAN was performed. The results indicated that evolution of arteritis can be classified into 4 stages. Coexistence of different stages was common (50%) in the same or different specimens. The initial (acute) stage shows endothelial loss and fibrin thrombi with neutrophil infiltration without obvious internal elastic lamina disruption and medial fibrinoid necrosis. The second (subacute) stage has mixed cell infiltrates showing a unique intimal target-like fibrinoid necrosis with fibrinoid leakage extending through the disrupted sites of the internal elastic lamina to the media. The third (reparative) stage shows intimal fibroblastic proliferation and perivascular neovascularization with predominant infiltrates of histiocytes and lymphocytes. The final (healed) stage has minimal cellular inflammation with occlusive intimal thickening. Overall, our results show that there are 4 stages in the evolution of C-PAN. The initial change occurs in the intima, and the role of internal elastic lamina in preventing intimal fibrinoid necrosis from discharging into the media may account for the development of target-like fibrinoid necrosis in C-PAN.

Cutaneous pseudovasculitis represents a heterogeneous collection of disorders that are capable of simulating cutaneous vasculitis and can be broadly classified into diseases that produce hemorrhage (petechiae, purpura, and ecchymoses) or vessel occlusion with resultant livedo, cyanosis, ulcers, digital necrosis, and/or gangrene. Overlap is not uncommon, but if present, one mechanism dominates. Hemorrhagic pseudovasculitis is due to vessel wall dysfunction (incompetence), which can be related to diverse factors that include vessel wall deposition of metabolic substances (amyloid, calcium), nutritional deficiencies (scurvy), nonvasculitic inflammatory purpura (pigmented purpuric dermatitis, arthropod, viral and drug reactions), degeneration of the vessel wall and supporting stroma (senile/solar purpura), direct vessel wall invasion of infective organisms, coagulation-fibrinolytic disorders (eg, thrombocytopenia), and vessel wall trauma. Cyanotic-infarctive pseudovasculitis is due vaso-occlusion by emboli, thrombi, or fibrointimal hyperplasia (endarteritis obliterans) and includes varied conditions such as purpura fulminans, Coumadin necrosis, antiphospholipid antibody syndrome, cardiac myxoma, cholesterol embolization, calciphylaxis, and radiation arteritis. Delayed and inappropriate diagnosis of pseudovasculitis leads to incorrect management and exposure to potentially deleterious treatment modalities such as corticosteroids and cytotoxic agents. The diagnosis of a pseudovasculitic disorder requires a high index of suspicion and should always be part of the differential diagnosis of vasculitis. Skin biopsy is a crucial step in differentiating pseudovasculitis from authentic vasculitis; absence of histologic evidence of vasculitis, particularly after multiple biopsies, should direct evaluation and diagnosis towards pseudovasculitis.

Most biopsies of cutaneous vasculitis will exhibit a small vessel neutrophilic vasculitis [leukocytoclastic vasculitis (LCV)] that is associated with immune complexes on direct immunofluorescence examination or, less commonly, antineutrophilic cytoplasmic antibodies (ANCA) by indirect immunofluorescence testing. Is in uncommon for skin biopsy to reveal solely a neutrophilic arteritis signifying the presence of cutaneous polyarteritis nodosa or, if accompanied by significant lobular panniculitis, nodular vasculitis/erythema induratum. In other cases, cutaneous vascular damage (fibrinoid necrosis, muscular vessel wall disruption, or endarteritis obliterans) will be mediated by a nonneutrophilic inflammatory infiltrate. Eosinophilic vasculitis can be a primary (idiopathic) process that overlaps with hypereosinophilic syndrome, or it can be a secondary vasculitis associated with connective tissue disease or parasite infestation. Authentic cutaneous granulomatous vasculitis (versus vasculitis with extravascular granulomas) can represent a cutaneous manifestation of giant cell arteritis, an eruption secondary to systemic disease such as Crohn's disease or sarcoidosis, or a localized disorder, often a post-herpes zoster (HZ) phenomenon. Lymphocytic vasculitis is a histologic reaction pattern that correlates with broad clinical differential diagnosis, which includes connective tissue disease - mostly systemic lupus erythematosus (SLE), endothelial infection by Rickettsia and viruses, idiopathic lichenoid dermatoses such as perniosis or ulcerative necrotic Mucha-Habermann disease, and angiocentric cutaneous T-cell lymphomas. Skin biopsy extending into the subcutis, identifying the dominant inflammatory cell and caliber of vessels affected, extravascular histologic clues such as presence of lichenoid dermatitis or panniculitis, and correlation with clinical data allows for accurate diagnosis of these uncommon vasculitic entities.

A broad and diverse spectrum of vasculitic syndromes exists. These syndromes affect the skin with varying levels of associated systemic manifestations, running the gamut from a self-limited, localized, cutaneous phenomenon to rapidly progressive, multiorgan disease. The majority of cases of cutaneous vasculitis will show a neutrophilic small vessel vasculitis that can be either a primary (idiopathic) disorder (eg, cutaneous leukocytoclastic angiitis) or a secondary disorder that is associated with drugs, infection (eg, streptococcal infection, viral hepatitis), or underlying disease (eg, connective tissue disease, malignancy). Biopsy is the gold standard for the diagnosis of cutaneous vasculitis and also necessary for the detection of cutaneous vascular immune complexes by direct immunofluorescence. Based on the type of vessel disrupted by inflammation (small and/or muscular), the distribution of vasculitis in the dermis and subcutis, and predominate inflammatory cell-type mediating vessel wall damage, a list of relevant differential diagnoses can be generated. This histologic information coupled with extravascular findings such as tissue eosinophilia, tissue neutrophilia, and/or granulomas, plus pathophysiologic markers such as direct immunofluorescent examination for immune complexes and serologic evaluation for antineutrophil cytoplasmic antibodies allows for more accurate diagnosis of specific vasculitic entities. Herein, we review both primary and secondary vasculitic syndromes that affect the skin and show a small vessel neutrophilic mediated vasculitis.

Vasculitis, inflammation of the vessel wall, can result in mural destruction with hemorrhage, aneurysm formation, and infarction, or intimal-medial hyperplasia and subsequent stenosis leading to tissue ischemia. The skin, in part due to its large vascular bed, exposure to cold temperatures, and frequent presence of stasis, is involved in many distinct as well as un-named vasculitic syndromes that vary from localized and self-limited to generalized and life-threatening with multi-organ disease. To exclude mimics of vasculitis, diagnosis of cutaneous vasculitis requires biopsy confirmation where its acute signs (fibrinoid necrosis), chronic signs (endarteritis obliterans), or past signs (acellular scar of healed arteritis) must be recognized and presence of extravascular findings such as patterned fibrosis or collagenolytic granulomas noted. Although vasculitis can be classified by etiology, many cases have no identifiable cause, and a single etiologic agent can elicit several distinct clinicopathologic expressions of vasculitis. Therefore, the classification of cutaneous vasculitis is best approached morphologically by determining vessel size and principal inflammatory response. These histologic patterns roughly correlate with pathogenic mechanisms that, when coupled with direct immunofluorescent examination, anti-neutrophil cytoplasmic antibody (ANCA) status, and findings from work-up for systemic disease, allow for specific diagnosis, and ultimately, more effective therapy. Herein, we review cutaneous vasculitis focusing on diagnostic criteria, classification, epidemiology, etiology, pathogenesis, and evaluation of the cutaneous vasculitis patient.