Vascular dermatosis section I allergic cutaneous vasculitis allergic cutaneous vasculitis is caused by a variety of reasons mainly involving the superficial dermal small blood vessels of allergic inflammatory skin disease, preferably in the limbs, to the lower leg, ankle is particularly significant. Clinical manifestations of papular purpura, wind, small water, polymorphic erythema, small nodules, erythema and nodules are more common, the course of the disease is chronic, can be delayed up to several years. The etiology of cutaneous vasculitis can be summarized as follows: ① idiopathic: 45% to 55%, most of the cause is unknown; ② infectious: 15% to 20%, can be caused by bacterial, viral, parasitic and fungal infections; ③ inflammatory diseases: 15% to 20%, patients with a combination of systemic lupus erythematosus, rheumatoid arthritis, desiccation syndrome, leucosis, inflammatory bowel disease and so on; ④ drugs: 10% to 15%, often caused by Drugs: accounting for 10% to 15%, often caused by antibiotics, oral contraceptives, anticonvulsants, phenothiazine antipsychotic drugs, antithyroid drugs, retinoic acid drugs, etc. Recently, the application of increased influenza vaccine, interferon and cytokine antagonists can also induce this disease; ⑤ Tumor: accounting for 5%, mainly originating in the bone marrow or lymphatic system of the tumor. The pathogenesis of this disease has not been fully understood, may be related to the allergic reaction (mainly type Ⅲ and type Ⅳ allergic reaction). Clinical manifestations: I. The cutaneous vasculitis damage is first seen in both calves, especially in the lower 2/3 of the calves, and is scattered, not limited to the extensor or flexor surfaces. In the process of recurrent attacks, it gradually involves the thighs and buttocks, and occasionally the forearms, with the lower thighs on both sides being the most common. Patients first feel local pain and pressure, and then touch the subcutaneous nodules, the number of often within 10, when other parts of the involvement, not only the number of damage increases, and due to the different parts of the damage, the shape of the damage is also slightly varied. Generally, they are about the size of broad beans to prunes, with palpable edges and medium hardness. Second, the initial damage is small and deep, so it is mostly skin color, or light red to bright red, with the prolongation of the duration, the red color can be deepened. Within 3 to 4 weeks, the red color fades first, leaving a mildly pigmented spot, while the nodular damage fades completely later. There is a more characteristic type of lesion, which lasts longer and is slightly larger than the previous lesions, with a purplish or dark red color and a smooth, shiny, even flaky, or tender central skin that never breaks down and does not atrophy and dimple after absorption. Damage on the buttocks and thighs are deeper and generally harder, the skin is not red or light red, and most are only palpable. Posterior ankle lesions were flattened round nodules with pale red skin and marked edema of the surrounding tissues. All the damages are scattered distribution, and it is rare to see those who tend to expand and merge. Systemic symptoms vary according to the urgency of the onset of the disease, usually drowsiness and malaise, or loss of appetite. Most cases do not have fever, a few cases of low fever in the afternoon, elevated after exertion; or in the days before and after the onset of nodules high fever. What is more special is that a few patients have chills or even chills in the afternoon, followed by fever, sweating and fever at midnight, and the next morning as usual. There are no cases of persistent hyperthermia. During the onset of damage, the lower limbs are sore and weak, and the muscles are swollen and painful. If the number of damages is large, mild edema may appear in the lower part of calves. Wandering pain in the large joints of the limbs, mostly in the knee joints, without redness, swelling and dysfunction. When other systems are involved, there are different manifestations 1, vasculitis involving the lungs: diffuse, interstitial or nodular lesions appear, and there can be cough, shortness of breath, dyspnea and other manifestations. 2, Kidney: appear hematuria, proteinuria, the incidence is high, often earlier renal decompensation. 3.Liver: discomfort in the liver area, liver function impairment. 4, vasculitis involving cardiovascular: the appearance of pulseless, bilateral limb blood pressure difference increases. 5, vasculitis involving the nervous system: due to lesions of blood vessels supplying blood to the skull, causing symptoms of cerebral ischemia, intracranial vasculitis may cause intracranial hemorrhage or nodular lesions. Vascular lesions supplying peripheral nerves can cause neuropathy and neurosensory and motor disorders. 6, nasopharynx: in Wegener’s granulomatosis (one of the vasculitis), there can be granulomatous lesions in the nasopharynx, nasal congestion, nasal bleeding and other symptoms. 【Diagnosis】 1. Chronic passage, recurrent episodes, predominantly distributed in both lower limbs. 2, The rash is erythema, papule, purpura, small water, nodule, wind ball, ulcer and other polymorphic damage. 3. Increased white blood cell count and rapid blood sedimentation. 4. Increase in anti-“O” value. 5, Histopathology shows non-specific adipose tissue inflammation in the upper part of the subcutaneous tissue and inflammatory reaction of the dermis.