Allergic purpura, an allergic vasculitis invading fine arteries and capillaries of the skin and other organs, is often associated with abdominal pain, arthralgia, and renal damage, but not reduced platelets. It is thought that allergic purpura and allergic cutaneous vasculitis belong to the same spectrum of diseases.
I. Common site of onset
Extremities, especially the lower extremities and buttocks
II. Etiology
It may be related to streptococcal infection, viral infection, drugs, food, insect bite, etc. The mechanism of occurrence is due to the combination of antigen and antibody to form immune complexes deposited in the vascular wall, which activates complement and leads to inflammation in and around the capillary and small vessel walls, resulting in increased permeability of the vessel walls, thus producing various clinical manifestations.
Clinical manifestations
It occurs in children and adolescents, and may start with fever, headache, arthralgia, and general discomfort. The skin lesions may appear as pinhead to soybean-sized petechiae, bruises or urticaria-like rash, and in severe cases, blisters, hemorrhages or even ulcers may occur. The skin lesions are usually found on the extremities, especially on the lower extremities and buttocks. The lesions are symmetrically distributed, appear in batches, and are prone to recurrence. Those with skin damage only are called simple purpura, those with abdominal pain, diarrhea, blood in stool and even gastrointestinal bleeding are called gastrointestinal purpura; those with joint swelling, pain and even joint effusion are called joint purpura; those with hematuria, proteinuria and kidney damage are called renal purpura.
IV. Diagnosis
It is not difficult to diagnose when purpura of both lower limbs, with abdominal pain, arthralgia or kidney damage. However, when the systemic symptoms appear before the skin purpura, it is easy to be misdiagnosed as rheumatoid arthritis or acute abdomen, and it needs to be clinically distinguished from these diseases and other types of purpura and vasculitis.
V. Treatment
1.Etiology treatment
Actively search and treat the possible causes.
2.Medication
Antibiotics: appropriate antibiotics can be used for those with infectious factors.
Antihistamines: applicable to simple purpura, can use rutin, vitamin C, calcium, aniloxin or haemostasis at the same time.
Aminophenyl sulfone:Early selection is effective.
Glucocorticoid:Applicable to severe skin damage or joint type, abdominal type, renal type purpura.
Immunosuppressants:For patients with recalcitrant chronic nephritis, cyclophosphamide or azathioprine may be used. It can be combined with glucocorticoids.
Symptomatic treatment:antipyretic and analgesic drugs such as indomethacin, fenbendazole for fever and arthralgia; scopolamine orally or intramuscularly, or atropine intramuscularly for abdominal pain.
Other treatment:Cimetidine, compound salvia injection, rehmannia, dextran-40, dipyridamole, etc. have been reported to cure allergic purpura respectively.
3.Plasma replacement
This method can effectively remove the immune complexes in blood circulation, thus preventing vascular obstruction and infarction. It is suitable for abdominal and renal type patients who have a large amount of immune complexes in the plasma.