OVERVIEW
Allergic vasculitis is one of the most common vasculitides, and was once known as leukocyte-crushing vasculitis, necrotizing nodular dermatitis, hypersensitivity vasculitis, nodular dermal allergic rash, allergic small arteritis, and allergic vasculitis, etc. Clinically, patients are often characterized by obvious skin damage or concomitant involvement of other organs as the prominent manifestation. Pathologic histologic examination shows fibrinoid necrosis of the vascular wall of small blood vessels, massive perivascular neutrophilic infiltration and nuclear fragmentation, and erythrocyte spillage, among other phenomena. Except for fulminant and severe visceral damage, the prognosis is generally good and recovery can be achieved within a few weeks.
Etiology
The disease is mainly caused by exogenous antigens. These exogenous antigens broadly include 3 categories.
1. Drugs
These include penicillin and its derivatives, sulfa, aspirin, etc.
2.Chemical substances
Such as insecticides, herbicides, petroleum agents.
3. In vitro proteins
Snake venom serum and various desensitizers.
Of these three types of allergens, drugs are the most common.
Symptoms
The onset of allergic vasculitis can be rapid or slow. The more common systemic symptoms include fever, malaise, fatigue, etc. The local manifestations are mainly skin symptoms, and a few patients have extracutaneous involvement, such as joints, kidneys, lungs and digestive system.
1. Skin manifestations
Skin lesions are mostly symmetrical, often distributed in the lower limbs and buttocks, can also occur in the upper limbs and chest and back, skin damage is polymorphic changes, mainly erythema, purpura, acne, papules, blood blisters, nodules and necrotic ulcers, chronic patients may occasionally have reticular cyanotic macules, the rash is often the beginning of the millet to mung bean red maculopapular eruptions and purpura, and soon develops into a palpable purpura, a little bit protruding from the skin surface, palpable with the hand, fingertip pressure does not fade, and the non-inflammatory purpura is easily distinguishable from the non-inflammatory purpura, which is often the most common skin lesions in patients. It is easy to distinguish from non-inflammatory purpura. The rash may vary in size from a pinprick to a fava bean. Small rashes are usually asymptomatic, while large or intermingled rashes may be painful. The rash flares up irregularly, lasts 1 to 4 weeks and subsides, and may leave pigmented patches. Some patients have severe skin lesions, epidermal necrosis, ulcers, scabs and atrophic scars after healing.
2. External skin manifestations
When joints are involved, there may be joint pain, but usually there is no redness, swelling and fever. When the lungs are invaded, patients have shortness of breath, hemoptysis and pleural effusion. Abdominal pain, nausea, upper gastrointestinal bleeding suggests gastrointestinal involvement. Central nervous system lesions include headache and diplopia. Cardiac involvement is rare and is characterized by cardiac arrhythmia, which can lead to heart failure in severe cases. In renal damage, edema and hematuria are seen.
Examination
1. Laboratory examination
(1) Blood test: blood eosinophils are often increased, white blood cell count can be increased, blood sedimentation is increased, hyperglobulinemia, ADP and prostaglandin can be increased, usually no anemia, platelet count is normal, bleeding and clotting time is normal. There is IgG-IgM cryoglobulinemia, and laboratory tests show hypergammaglobulinemia and hypocomplementemia, RF and HBsAg may be positive.
(2) Urine examination may have protein, red blood cells, white blood cells and tubular pattern. In severe cases, there may be nephrotic syndrome range proteinuria, and there may be increased urea nitrogen and creatinine in renal decompensation.
(3) Routine fecal examination Parasite eggs and red blood cells can be seen in some patients, and occult blood test can be positive.
(4) Bone marrow image Normal bone marrow image.
(5) Capillary brittleness test is positive.
2. Auxiliary examination
(1) Histopathologic examination: Diffuse perivascular inflammation with neutrophils gathering around blood vessels. Immunofluorescence shows IgM and C3 deposits in the dermal vascular wall. ① Skin changes The main pathologic feature of allergic vasculitis is acute fibrinoid necrosis that begins in the intima or subendothelial stroma and then spreads throughout the vessel wall with a significant pleomorphic cell reaction and eosinophilic infiltration. The progression of the lesions at the vascular lesions is at the same time period, unlike in nodular polyarteritis where all stages are present. Examination of the skin tissue under the dermal papillae to the reticular layer of the fine arteritis phlebitis and capillaritis vasodilatation, endothelial cell edema and exudation, lumen narrowing with thrombosis, and fibrin-like degeneration or necrosis of the vessel wall. Early onset of vascular perivascular neutrophilic leukocyte-based cellular infiltration, visible leukocyte fragmentation and nuclear dust and erythrocyte extravasation, etc., while the late onset of the mononuclear cell infiltration is predominant. In addition to the skin, the kidneys are the most susceptible part of the disease. Normal or enlarged size of the kidneys can be seen by naked eye, and there are hemorrhages on the surface. Light microscopy can be seen smaller interlobular arteries, arterioles, veins and capillaries with fibrinoid necrosis, the most significant glomerular lesions, glomeruli around the occasional granulomatous lesions. Intracapillary cellular hyperplasia with segmental or circumscribed epithelioid crescents and diffuse necrotizing glomerulonephritis are seen The disease has a more frequent type of renal pathology, with round cellular infiltration and hemorrhage in the renal interstitium of the crescentic nephritis with no or few immune complexes. Some tubules atrophy. Immunofluorescence showed little or no immunoglobulin component of IgG, IgM, and complement deposits in the mesangial area and capillary wall, but more fibrinogen deposits in the glomerular capsule and glomerular necrotic vascular area. Electron microscopy did not show obvious characteristic changes or more electron dense material.
The characteristic lesion of renal involvement in allergic vasculitis is necrotizing glomerulonephritis or focal necrotizing glomerulonephritis. Diffuse necrotizing glomerulonephritis is seen in worsening cases.
(2) X-ray examination Lung involvement may show focal or diffuse pulmonary infiltrates, or small nodular forms, and occasionally pleural effusion on chest radiograph.
Diagnosis
Based on the above pathogenetic features, the diagnosis of typical allergic vasculitis is not difficult. 1990, the American Rheumatism Association (ARA) established a diagnostic criterion for allergic vasculitis
1. Age of onset >16 years.
2. History of drug use prior to illness.
3. Palpable purpura.
4. maculopapular rash, i.e., a rash in one or more areas of the skin that is flattened in size and elevated above the surface of the skin.
5. Sections of small veins or arteries in the skin show intravascular or extravascular neutrophilic infiltration.
Allergic vasculitis can be diagnosed if 3 or more of the above 5 items are met. The sensitivity of this criterion is 71% and the specificity is 93%.
Differential diagnosis
1. Anaphylactic purpura
Allergic purpura is most common in children, and the skin damage manifests as subcutaneous hemorrhagic macules and macules without polymorphic skin lesions. The vast majority have the typical triad of symptoms (purpura, arthralgia and abdominal pain), and more than half have hematuria, proteinuria, nephrotic syndrome, and even renal failure. Renal pathology suggested focal segmental sclerosing glomerulonephritis or diffuse thylakoid proliferative glomerulonephritis, and a few severe cases showed crescentic nephritis. Immunofluorescence showed deposition of IgA and complement in the glomerular thylakoid zone, and the pathologic changes were similar to those of primary IgA nephropathy. The effective treatment of this disease is very important for the identification and removal of the cause, especially the discontinuation of suspected antigenic sensitizing drugs has a key role in determining the prognosis. Other principles of treatment are basically similar to that of polyarteritis nodosa.
2. Thrombocytopenic purpura
Thrombocytopenic purpura is characterized by large subcutaneous bruises and a marked decrease in platelet count.
3. Erythema multiforme
The lesions show edematous erythema on the backs of the hands and feet, with a dark red center and target-like appearance.
Treatment of erythema multiforme
1. Causative treatment
Rapidly find out the sensitizing drugs or chemicals, and warn the patients to stop and ensure that they will not be exposed to such substances in the future. Eliminate the infection.
2. Drug treatment
(1) Glucocorticoids are effective in most patients. The dose of these drugs should be determined by the severity of the disease. The dose should be slowly reduced to the minimum maintenance level or as directed by the physician once symptoms improve.
(2) antihistamines If the patient’s condition is mild, only a small portion of the skin is involved and there is no damage to internal organs, no special treatment is needed, and the use of this type of medicine can be dealt with.
(3) Sulfone drugs Its mechanism of action is not known, may be related to the stabilization of lysosomal membranes and other effects, some patients can effectively control the condition with only aminophenyl sulfone.
(4) Immunosuppressants If the patient does not respond well to glucocorticoids or cannot tolerate the side effects of glucocorticoids, immunosuppressant treatment can be considered.
(5) Leukocyte function inhibitors
(6) Antibiotics The use of antibiotics is extremely necessary for patients with co-infections.
(7) Non-steroidal anti-inflammatory drugs (NSAIDs) are mainly symptomatic treatments that are effective in patients with fever and joint pain.
Questions you may be concerned about
How to treat allergic vasculitis
The treatment of allergic vasculitis includes etiologic treatment and drug treatment.
1. Etiological treatment: allergic vasculitis is also known as allergic vasculitis. If the lesions are mild and there is no organ involvement, the allergens should be removed and the patients should be avoided from contacting the substances to avoid reoccurrence of the disease.
2. Drug treatment: allergic vasculitis patients with fever, fatigue, malaise, skin damage and other symptoms can follow the doctor’s instructions to take dexamethasone, prednisone and other glucocorticoids, and those who are not effective can be combined with cyclophosphamide, azathioprine and other immunosuppressant treatment.
It is recommended that patients with allergic vasculitis go to the rheumatology and immunology department of the hospital in a timely manner, under the guidance of a specialist for standardized treatment, and avoid self-medication, so as not to delay the condition.