Eosinophilic panniculitis: report of three cases

Eosinophilic panniculitis, characterized by a prominent infiltration of subcutaneous fat with eosinophils, has been identified in patients with a variety of associated clinical conditions. Burket and Burket reported the first case in 1985. ¹ To our knowledge, more than 30 additional patients have been described since this initial case report. The study of 18 patients with biopsy diagnoses of eosinophilic panniculitis by Winkelmann, et al . in 1986 revealed diverse patterns of systemic disease, including Wells' syndrome, vasculitis, atopy, and erythema nodosum. ² We report three male patients of eosinophilic panniculitis with various clinical signs, two of whom had history of trauma or tuberculous pleurisy.     

Acute infectious id panniculitis/panniculitic bacterid: a distinctive form of neutrophilic lobular panniculitis

Background: Lobular panniculitis encompasses lupus profundus, atypical lymphocytic lobular panniculitis, erythema induratum and subcutaneous Sweet’s syndrome, while septal panniculitis includes erythema nodosum and fibrosing dermal processes of burn out necrobiosis lipoidica and morphea profundus. Panniculitis may represent a sign of systemic disease and/or a modified immune response to hematogenously disseminated antigen. Methods: We describe 10 cases of sterile neutrophilic dominant lobular panniculitis that represented an id reaction to non‐tuberculous stimuli. Results: Four males and six females had sudden tender non‐ulcerated lower extremity nodules with preceding non‐tuberculous infectious triggers. Three also had upper extremity lesions. Biopsies showed dominant neutrophilic infiltrate with subcutaneous microabscesses (7), extravascular granulomatous infiltrates (5), thrombotic microangiopathy (5) and necrotizing vasculitis (5). Stains evaluating microbial pathogens were negative. Lesions resolved with antibiotic treatment and/or abscess drainage; no case recurred. Medical histories included atopic diathesis (4), primary antiphospholipid antibody syndrome (1), ulcerative colitis (1) and acute lymphocytic leukemia (1). Serologies showed polyclonal hypergammaglobulinemia, cold agglutinins and cryofibrinogens. Conclusions: We propose the term acute infectious id panniculitis for cases of neutrophilic lobular panniculitis triggered by non‐tuberculous infectious stimuli. This course may be self‐limited. Microvascular cofactors and/or procoagulant states may be pathogenetically important. Recognizing this entity may circumvent the need for an exhaustive evaluation for other causes of neutrophilic lobular panniculitis.     

Erythema nodosum-like lesions in Behçet''s syndrome: a histopathologic study of 30 cases

Thirty patients who fulfilled the criteria for complete and incomplete types of Behçet's syndrome were studied to determine the histopathologic changes of erythema nodosum-like lesions. Lymphocytic vasculitis was observed in 12 (40%) of the cases, but it was only focal in areas of severe lymphocytic inflammation and only mild in degree. No diffuse vasculitis was seen. It is our opinion that the observed lymphocytic vasculitis is only secondary to moderate or severe lymphocytic inflammation. Twelve cases (40%) revealed septal panniculitis, 10 cases (33%) demonstrated lobular panniculitis with moderate to marked inflammation and fat cell necrosis, and 8 cases (27%) showed mild and nonspecific inflammation in the panniculus. Therefore, there is a spectrum of histopathologic changes of erythema nodosum-like lesions in Behçet's syndrome, similar to that of erythema nodosum secondary to other systemic disorders.     

Cutaneous vasculitis update: neutrophilic muscular vessel and eosinophilic, granulomatous, and lymphocytic vasculitis syndromes

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.     

Panniculitis

The classification of inflammatory disorders of the subcutaneous tissue has mystified dermatologists for decades. Overlapping clinical and histologic features, and a lack of specific treatments have added to the confusion. This article initially classifies the various panniculititides by their primary histopathologic pattern: (1) septal panniculitis without vasculitis, (2) septal panniculitis with vasculitis, (3) lobular panniculitis without vasculitis, and (4) lobular panniculitis with vasculitis. Subsequently, we describe the key clinical findings in the most important forms of panniculitis. We begin with the most common form of panniculitis, erythema nodosum. Indeed, in many patients suspected of having panniculitis, a worthwhile question to consider initially might be, "Is this, or is this not, erythema nodosum?" before engaging in an elaborate (and expensive) exercise in differential diagnosis.     

Eosinophilic panniculitis associated with chronic recurrent parotitis

A 37-year-old woman presented with recurrent erythema nodosum-like lesions on her arms and legs that were preceded by chronic recurrent parotitis. Microscopic examination revealed a mixed lobular and septal panniculitis with many eosinophils and multiple eosinophilic flame figures similar to those seen in Wells' syndrome. The dermis was not involved. The classification, differential diagnosis, and possible pathomechanisms of eosinophilic panniculitis are discussed.     

Propylthiouracil-induced ANCA-positive erythema nodosum treated with thalidomide

Background Propylthiouracil (PTU), one of the mainstays of antithyroid therapy drugs, can lead to antineutrophil cytoplasmic antibody (ANCA) positivity and skin lesions. PTU‐induced ANCA‐positive vasculitis is rare and even more rare is erythema nodosum. Objective To report a case of a 57‐year‐old woman with hyperthyroidism who developed myeloperoxidase (MPO)‐ANCA erythema nodosum after PTU treatment for 11 months. Methods Skin biopsy demonstrated septal panniculitis without vasculitis. PTU‐induced ANCA‐positive erythema nodosum was made. Results With discontinuation of PTU and initiation of thalidomide, skin lesions resolved completely in three weeks, and after three months, the titers of MPO‐ANCA and perinuclear‐ANCA (p‐ANCA) had decreased remarkably. At 14‐month follow‐up, the patient was asymptomatic, but low levels of ANCA titers persisted. Conclusions This report indicated that ANCA positive erythema nodosum could develop following PTU treatment. Thalidomide has been proven to be helpful and averted the adverse effects from systemic corticosteroids and other immunosuppressive drugs in this patient.     

Necrotizing eosinophilic folliculitis as a manifestation of the atopic diathesis

BACKGROUND: Eosinophilic folliculitis (EF) is an idiopathic eruption of sterile pustules and papules involving the trunk, face, and extremities, associated in many cases with human immunodeficiency virus (HIV) infection. The classic histopathology is one of follicular-based, eosinophilic spongiosis with variable microabscess formation. We describe nine HIV-negative patients who manifested a novel form of pustular EF in the setting of atopy. MATERIALS AND METHODS: Paraffin sections of skin biopsies from ten patients, stained with hematoxylin and eosin and special preparations to evaluate for microbial pathogens, were examined. Detailed clinical histories and serologic studies were obtained. RESULTS: Among the clinical presentations in seven men, two women, and one girl (age range, 11-62 years) were ulcerative and/or nodular plaques mainly on the face and/or extremities, sometimes in an annular configuration. The clinical considerations included deep mycotic infection, ulcerative herpes, systemic vasculitis, Mucha Haberman disease, and pyoderma gangrenosum. All patients had a personal and/or family history of atopy. Co-existent medical illnesses included psoriasis, lupus erythematosus, and lymphoproliferative disease. One patient was on a calcium channel blocker, one on multiple antidepressants, and two on antihistamines, all of which are associated with immune dysregulation. All skin biopsies showed variable intra- follicular eosinophilic microabscesses, follicular necrosis, folliculocentric necrotizing eosinophilic vasculitis, marked degeneration of connective tissue fiber elements, and striking tissue eosinophilia, including flame figure formation and dermal eosinophilic abscesses. Apart from commensals, such as Pityrosporum and Demodex, microbial pathogens were not identified. CONCLUSIONS: The presentations differed from conventional EF by virtue of a strong association with atopy and by the presence of ulceration, nodule formation, follicular and dermal necrosis, and eosinophilic vasculitis. We propose the term "necrotizing eosinophilic folliculitis," and suggest that the basis of this novel form of EF is an unrepressed T-helper lymphocyte type 2 (Th2)-dominant response to various epicutaneous stimuli in patients with atopy, the prototypic immune dysregulatory state associated with a Th2-dominant cytokine milieu.     

33例脂膜炎与结核感染相关性分析

 目的 了解不同类型的脂膜炎患者与结核感染的相关性。方法 纳入2019年1月—2021年12月就诊于常德市第一人民医院33例脂膜炎患者的临床资料，对其临床特征、病理特征、与结核感染的相关性、治疗情况及随访情况进行分析。结果 ①33例脂膜炎患者中,结节性红斑24例，硬红斑9例，男女比例为1 ∶ 4.5，平均年龄46岁，平均病程10个月。②临床发病部位集中在四肢，均伴有疼痛。30例（90.91%)表现为红斑、结节、肿胀，其中1例硬红斑（3.03%）出现溃疡。6例(18.18%)出现发热、咳嗽、盗汗。2例硬红斑患者同时伴有或先后出现丘疹性坏死性结核疹，2例结节性红斑患者伴有全身多关节疼痛。③22例（66.67%,包括9例硬红斑、13例结节性红斑)伴结核分支杆菌潜伏感染（LTBI）。硬红斑患者结核感染阳性率高于结节性红斑患者（P＝0.020）。④皮损组织病理表现为间隔性脂膜炎11例、小叶性脂膜炎3例、混合性脂膜炎19例。与结核感染相关的22例脂膜炎患者病理下多可见上皮细胞肉芽肿、多核巨细胞以及干酪样坏死，其余11例均可见真皮层血管周围及脂肪间隔淋巴细胞浸润，且均未见上皮样肉芽肿及多核巨细胞。33例患者抗酸染色、PAS染色、直接免疫荧光均未见阳性表现。⑤22例与结核感染相关患者中，接受抗结核治疗15例，治愈率为68.18%，拒绝接受抗结核治疗患者7例，治愈率为14.29%。11例结核感染不相关患者采用免疫调节联合治疗，治愈率为100%。所有患者均未出现严重药物不良反应。结论 硬红斑患者的结核感染阳性率比结节性红斑患者高。在结核感染相关的脂膜炎患者中，接受抗结核治疗者治愈率比免疫调节联合治疗者高；对于未发现结核感染证据的结节性红斑，免疫调节治疗可能有效。结节性红斑患者的发病原因可能与结核感染相关。在结核高发地区，结节性红斑患者完善相关筛查极其重要。     

Eosinophilic cellulitis: five cases

Five cases of eosinophilic cellulitis or Wells' syndrome are described. While only few children have been included in earlier reports, 4 of the 5 patients in the present paper were below 10 years of age, with the youngest being only 20 months when the disease started. One of the children developed hard and tender subcutaneous swellings on the scalp, the histology of which showed extensive subcutaneous necrotizing granulomas. Similar lesions have not been described previously in connection with eosinophilic cellulitis. Eosinophilic cellulitis may be called a rare disease. However, it is important that clinician and histopathologist are both acquainted with the pathological features of this condition, as the disease often responds readily to steroid therapy.     

Nodules on the legs. A clinical, histological and immunohistological study of 82 patients representing different types of nodular panniculitis.

Eighty-two cases of nodular panniculitis of the legs were examined clinically, histologically and immunohistologically. Clinically the cases could be divided into four groups: typical erythema nodosum (ENty) (35 cases), erythema nodosum migrans (ENmi) (11 cases), erythema induratum (EI) (11 cases) and the remaining 25 cases not consistent with the others as "non-definite panniculitis" (NDP). The main histological categories were septal panniculitis and lobular panniculitis, the former including erythema nodosum, both typical and migrans, the latter EI and NDP. Lobular panniculitis was divided into three subgroups in which the most prominent histological features were epithelioid cell granuloma, vasculitis and palissading granuloma, respectively. Immunoglobulins in the vessel walls were found in 5 of the 46 cases of erythema nodosum, in 19 of the 36 EI and NDP cases and, in the histological groups in 4 of the 43 cases of septal panniculitis and in 19 of the 35 cases of lobular panniculitis, respectively. Fibrin was found in the walls of the papillary capillaries and deep dermal vessels in the majority of cases of lobular panniculitis. In EI and NDP the follow-up time was 40 months, on average. Twenty-two patients were treated with antituberculous drugs, 15 became symptomless, as did 5 of the 12 patients who were not treated at all.     

Erythema nodosum

Erythema nodosum is the most frequent clinico-pathological variant of the panniculitides. The disorder is a cutaneous reaction consisting of inflammatory, tender, nodular lesions, usually located on the anterior aspects of the lower extremities. The process may be associated with a wide variety of diseases, being infections, sarcoidosis, rheumatologic diseases, inflammatory bowel diseases, medications, autoimmune disorders, pregnancy, and malignancies the most common associated conditions. The typical eruption consists of a sudden onset of symmetrical, tender, erythematous, warm nodules and raised plaques usually located on the shins, ankles and knees. Often the lesions are bilaterally distributed. At first, the nodules show a bright red color, but within a few days they become livid red or purplish, and finally they exhibit a yellow or greenish appearance taking on the look of a deep bruise. Ulceration is never seen and the nodules heal without atrophy or scarring. Some clinical variants of erythema nodosum have been described under different names, including erythema nodosum migrans, subacute nodular migratory panniculitis, and chronic erythema nodosum, but probably they are just clinical variants which may all be included within the spectrum of erythema nodosum. Histopathologically, erythema nodosum is the stereotypical example of a mostly septal panniculitis with no vasculitis. The septa of subcutaneous fat are always thickened and variously infiltrated by inflammatory cells that extend to the periseptal areas of the fat lobules. The composition of the inflammatory infiltrate in the septa varies with age of the lesion. In early lesions edema, hemorrhage, and neutrophils are responsible for the septal thickening, whereas fibrosis, periseptal granulation tissue, lymphocytes, and multinucleated giant cells are the main findings in late stage lesions of erythema nodosum. A histopathologic hallmark of erythema nodosum is the presence of the so-called Miescher's radial granulomas, which consist of small, well-defined nodular aggregations of small histiocytes arranged radially around a central cleft of variable shape. Treatment of erythema nodosum should be directed to the underlying associated condition, if identified. Usually, nodules of erythema nodosum regress spontaneously within a few weeks, and bed rest is often sufficient treatment. Aspirin, nonsteroidal anti-inflammatory drugs, such as oxyphenbutazone, indomethacin or naproxen, and potassium iodide may be helpful drugs to enhance analgesia and resolution. Systemic corticosteroids are rarely indicated in erythema nodosum and before these drugs are administered an underlying infection should be ruled out.     

Panniculitis as the initial manifestation of brucellosis: a case report

Here, we describe a 38-year-old male with an abrupt manifestation acute panniculitis as unusual presentation of brucellosis. Brucellosis is a reemerging disease in Turkey, and the disease is primarily transmitted from farm animals to humans. Farmers and shepherds are the major risk groups for brucellosis in Anatolia. Brucellosis may involve almost all systems and organs, including the skin, and may mimic a wide range of illness and syndromes. Although the cutaneous manifestation of brucellosis is not disease specific, but it occurs in about 6%-13% of patients with brucellosis. Some of these lesions including rashes, papules, ulcers, abscess, erythema nodosum, ecchymosed skin rash, purpura, and vasculitis may be seen frequently in brucellosis, but panniculitis is rarely described. The case confirmed by positive blood culture had manifest skin lesion as an initial finding represented by lobular panniculitis with vasculitis.     

结节性红斑的病因学研究进展

结节性红斑是一种脂膜炎,常发生于双侧胫前,以红斑、痛性皮下结节为主要表现.青年女性好发.组织学表现为间隔性脂膜炎,伴多种炎症细胞浸润.确切的发病机制尚不明确,目前认为可能是一种迟发超敏反应,也有学者认为,是免疫复合物沉积在脂肪间隔的小静脉所致,引起嗜中性脂膜炎.病因复杂,与感染、系统性疾病、药物、激素水平、恶性肿瘤等因素相关.由于地区差异,病因可能有所不同.     

Histopathologic features of erythema nodosum--like lesions in Behçet disease: a comparison with erythema nodosum focusing on the role of vasculitis

Many patients with Beh?et disease (BD) develop lesions that clinically resemble those of erythema nodosum (EN) but differ from that condition with regard to their microscopic features. We examined 11 sections of EN-like lesions in BD and compared them with 9 sections of classic EN using routine histopathology and immunohistochemistry so as to form a comprehensive picture of the pathologic findings in BD and to determine the role of vasculitis in the formation of lesions. Erythema nodosum-like lesions of BD are characterized by panniculitis, usually lobular or mixed septal and lobular in pattern, with variable numbers of neutrophils, lymphocytes, and histiocytes as well as variable numbers of necrotic adipocytes. Vasculitis was noted in most EN-like lesions in BD. Scattered vessels showing lymphocytic vasculitis were evident in 6 sections, and foci of leukocytoclastic vasculitis were obvious in 4 sections, sometimes with phlebitis or arteriolitis. In specimens with classic EN, we did not observe vasculitis. Only the percentages of CD3+ lymphocytes and chloroacetate esterase-positive neutrophils in the infiltrating cells showed statistically significant differences (P < 0.05) between EN-like lesions in BD and EN through immunohistochemical and enzyme cytochemical studies. Because vasculitis in the EN-like lesions in BD was extensive and not limited to areas of severe inflammation, we believe that it is primary vasculitis. We suggest that vasculitis is an important pathologic event in EN-like lesions in BD but cannot determine the extent to which other pathologic changes such as septal or lobular panniculitis, fat necrosis, neutrophilic infiltration, or microabscess formation are secondary features.     

Immunological evaluation of erythema nodosum in tularaemia

During two tularaemia outbreaks in the Bursa region of Turkey in 1991, a total of 98 patients were diagnosed and evaluated. Thirteen of these patients had erythema nodosum, which is accepted as a secondary skin manifestation. The patients with erythema nodosum, 21 patients without any skin lesions, and 20 healthy controls were studied. Comparable elevations of levels of IgG, IgA, and IgM were detected in the two tularaemia groups. There was no difference in complement C3c and C4 levels between the groups. All of the patients with erythema nodosum had elevated circulating immune complex (CIC) levels, when compared with the patients without skin lesions and the control group. The acute phase response (C-reactive protein [CRP] and erythrocyte sedimentation rate [ESR]) of the erythema nodosum group was significantly higher than the patients with normal skin, and healthy controls (P> 0.001). Serum transferrin levels were significantly decreased in both of the tularaemia groups (P>0.001). Serum soluble interleukin-2 receptor levels (SIL-2R) were significantly elevated in both tularaemia groups (P>0.001), and the elevation was more marked in the erythema nodosum group (P> 0.05). Histopathologicai evaluation of biopsies from two patients with erythema nodosum showed dermal oedema, a perivascular lymphocytic infiltrate, and panniculitis. No immunoglobulin or complement deposits were detected on immunofluorescence. Erythema nodosum in the course of tularaemia is associated with many immunological changes, although it is not clear whether these findings are related to the increased tissue response, or whether they play a role in the pathogenesis of the erythema nodosum.     

A Case of Assisted Reproductive Therapy-induced Erythema Nodosum

Erythema nodosum is a common variant of panniculitis. It is characterized by tender erythematous nodule and plaque on the anterior aspect of the leg. The etiology is not fully understood. It may be associated with a variety of disorders, including infection, medication, autoimmune disorders, pregnancy, and malignancy. A 33-year-old Korean woman presented with 1 week history of painful erythematous plaques on both knees. She was 7 weeks pregnant with assisted reproductive therapy, and had been maintained on daily intramuscular progesterone injection for 4 weeks. Histological examination of the lesions revealed septal panniculitis without vasculitis. Two days after discontinuing progesterone injection, the symptoms and lesions started to resolve. Herein we present a case of erythema nodosum caused by progesterone injection for endometrial preparation.     

Erythema nodosum

Erythema nodosum is the most frequent clinicopathologic variant of panniculitis. The process is a cutaneous reaction that may be associated with a wide variety of disorders, including infections, sarcoidosis, rheumatologic diseases, inflammatory bowel diseases, medications, autoimmune disorders, pregnancy, and malignancies. Erythema nodosum typically manifest by the sudden onset of symmetrical, tender, erythematous, warm nodules and raised plaques usually located on the lower limbs. Often the lesions are bilaterally distributed. At first, the nodules show a bright red color, but within a few days they become livid red or purplish and, finally, they exhibit a yellow or greenish appearance, taking on the look of a deep bruise. Ulceration is never seen, and the nodules heal without atrophy or scarring. Histopathologically, erythema nodosum is the stereotypical example of a mostly septal panniculitis with no vasculitis. The septa of subcutaneous fat are always thickened and variously infiltrated by inflammatory cells that extend to the periseptal areas of the fat lobules. The composition of the inflammatory infiltrate in the septa varies with age of the lesion. In early lesions edema, hemorrhage, and neutrophils are responsible for the septal thickening, whereas fibrosis, periseptal granulation tissue, lymphocytes, and multinucleated giant cells are the main findings in late stage lesions of erythema nodosum. A histopathologic hallmark of erythema nodosum is the presence of the so-called Miescher's radial granulomas, which consist of small, well-defined nodular aggregations of small histiocytes arranged radially around a central cleft of variable shape. Treatment of erythema nodosum should be directed to the underlying associated condition, if identified. Usually, nodules of erythema nodosum regress spontaneously within a few weeks, and bed rest is often sufficient treatment. Aspirin, nonsteroidal antiinflammatory drugs, such as oxyphenbutazone, indomethacin or naproxen, and potassium iodide may be helpful drugs to enhance analgesia and resolution. Systemic corticosteroids are rarely indicated in erythema nodosum and before these drugs are administered an underlying infection should be ruled out.     

Erythema nodosum

Erythema nodosum is the most frequent clinicopathologic variant of panniculitis. The process is a cutaneous reaction that may be associated with a wide variety of disorders, including infections, sarcoidosis, rheumatologic diseases, inflammatory bowel diseases, medications, autoimmune disorders, pregnancy, and malignancies. Histopathologically, erythema nodosum is the stereotypical example of a mostly septal panniculitis with no vasculitis. The composition of the inflammatory infiltrate in the septa varies with age of the lesion. Treatment of erythema nodosum should be directed to the underlying associated condition, if identified.     

Panniculitis. Part I. Mostly septal panniculitis.

The panniculitides represent a group of heterogeneous inflammatory diseases that involve the subcutaneous fat. The specific diagnosis of these diseases requires histopathologic study because different panniculitides usually show the same clinical appearance, which consists of subcutaneous erythematous nodules on the lower extremities. However, the histopathologic study of panniculitis is difficult because of an inadequate clinicopathologic correlation, and the changing evolutionary nature of the lesions means that biopsy specimens are often taken from late-stage lesions, which results in nonspecific histopathologic findings. In addition, large-scalpel incisional biopsies are required. However, we believe that by obtaining appropriate biopsy specimens and with adequate clinicopathologic correlation, a specific diagnosis may be rendered in most cases of panniculitis. It must be accepted that all panniculitides are somewhat mixed because the inflammatory infiltrate involves both the septa and lobules; however, in general the differential diagnosis between a mostly septal and a mostly lobular panniculitis is straightforward at scanning magnification. Mostly septal panniculitides with vasculitis include leukocytoclastic vasculitis involving the small blood vessels of the septa; superficial thrombophlebitis resulting from inflammation and subsequent thrombosis of large veins of the septa; and cutaneous polyarteritis nodosa, which is a vasculitis involving arteries and arterioles of the septa of subcutaneous fat with few or no systemic manifestations. Often septal panniculitides with no vasculitis are the consequence of dermal inflammatory processes extending to the subcutaneous fat, such as necrobiosis lipoidica, scleroderma, subcutaneous granuloma annulare, rheumatoid nodule, and necrobiotic xanthogranuloma. However, in other cases, the inflammatory process is primarily located in the fibrous septa of the subcutis with or without involvement of the overlying dermis. The most frequently seen septal panniculitis is erythema nodosum, which, in fully developed lesions, is characterized histopathologically by Miescher's radial granulomas in the septa.