Reasons for purple patches on the body

Many parents find purple spots on their children's bodies when bathing them. They originally thought that the children fell and did not pay attention to them. However, they realized later that this was actually allergic purpura, an allergic vasculitis that invades the small arteries and capillaries of the skin and other organs. It is a common vasculitis in school-age children. So what are the specific manifestations of this disease? Let's learn about it together.

1. Skin

Most cases present with skin purpura as the first symptom. Skin lesions appear as pinpoint to soybean-sized petechiae, ecchymoses or urticaria-like rashes or pink maculopapular rashes that do not fade when pressed, which is purpura. Purpura may merge into patches and eventually turn brown. It usually disappears within 1 to 2 weeks without leaving any trace. In severe cases, blisters, blood blisters, necrosis and even ulcers may occur. The rash often occurs in weight-bearing areas, especially on the extensor side of the limbs, especially the lower limbs, around the ankle joints and buttocks. The lesions are symmetrically distributed, appear in batches, and are prone to recurrence. Only skin damage is also called simple purpura.

2. Digestive system

About 2/3 of cases present with gastrointestinal symptoms. It usually appears within 1 week of the rash. Common abdominal pain, often manifested as paroxysmal periumbilical pain and colic, abdominal pain may also occur in other parts of the abdomen. There may be tenderness, but rebound tenderness is rare. Accompanied by vomiting. About half of the children have positive fecal occult blood test, some may have bloody stools, or even vomit blood. If abdominal pain occurs before skin symptoms, it is easy to be misdiagnosed as an acute surgical abdomen or even undergo surgical treatment incorrectly. A small number of children may develop complications such as intussusception, intestinal obstruction, intestinal perforation and hemorrhagic enteritis. Patients with abdominal pain, diarrhea, bloody stools, and even gastrointestinal bleeding are also called gastrointestinal purpura.

3. Urinary system

Most cases develop gross hematuria, microscopic hematuria and proteinuria, or tubular urine 2 to 4 weeks after purpura onset. Urinary system symptoms may occur at any time during the course of the disease, and may also appear after the rash subsides or when the disease is dormant. The severity of the disease varies, and severe cases may cause renal failure and hypertension. More than half of the children's kidney damage can be cured clinically on its own. Patients with hematuria, proteinuria and renal damage are also called renal purpura.

4. Joints

Most children only experience swelling, pain, tenderness or arthritis in and around the joints, which may be accompanied by limited mobility. Large joints such as the knees and ankles are most commonly affected, but the wrists, elbows, and fingers may also be affected. Joint lesions are often transient and usually disappear within a few days without leaving joint deformities. Patients with joint swelling, pain, and even joint effusion are called articular purpura.

5. Others

Central nervous system symptoms are rare and include coma, subarachnoid hemorrhage, optic neuritis, and Guillain-Barré syndrome.