OVERVIEW

What is Henoch-Schönlein Purpura?

The formal name for Henoch-Schönlein purpura is "IgA vasculitis," also known as hemorrhagic capillary toxicosis or Schönlein-Henoch syndrome. It is a common immune-mediated vasculitis associated with IgA deposition^[1].

It is primarily characterized by increased capillary fragility and permeability, leading to blood extravasation, resulting in purpura (reddish-purple skin changes), as well as bleeding in mucous membranes and certain organs. Typically, there is no thrombocytopenia or coagulation disorder^[1,2].

What is purpura?

Purpura refers to bleeding under the skin or mucous membranes, causing red or purple discoloration^[3].

Purpura results from factors such as blood vessel wall damage or coagulation dysfunction, usually presenting as localized spontaneous bleeding in the skin or mucous membranes^[3].

What is the difference between Henoch-Schönlein purpura and idiopathic thrombocytopenic purpura?

Unlike Henoch-Schönlein purpura, idiopathic thrombocytopenic purpura is a complex acquired autoimmune disorder involving multiple mechanisms, also known as primary immune thrombocytopenia or immune thrombocytopenic purpura.

This condition occurs due to the patient's immune intolerance to their own platelet antigens, leading to immune-mediated excessive platelet destruction and suppressed platelet production, resulting in thrombocytopenia and mucocutaneous bleeding.

Both conditions exhibit noticeable skin purpura, but the key difference is that the former involves thrombocytopenia causing bleeding tendencies, while the latter has a normal platelet count^[2].

SYMPTOMS

Does purpura on the skin mean leukemia?

Purpura is just one manifestation of leukemia; it cannot be concluded that purpura on the skin means leukemia.

Generally, leukemia refers to a group of malignant diseases of hematopoietic stem/progenitor cells, divided into acute and chronic types. Acute leukemia, commonly known as blood cancer, involves the excessive proliferation of abnormal primitive and immature cells (leukemia cells) in the bone marrow, which suppress normal hematopoiesis. Therefore, when leukemia causes thrombocytopenia or coagulation dysfunction, it may present as skin bleeding (e.g., purpura), often accompanied by anemia, infections, and infiltration^[2].

Additionally, besides allergic purpura and leukemia, skin purpura can occur in various other conditions, such as simple purpura (a vascular bleeding disorder of unknown cause), idiopathic thrombocytopenic purpura (skin and mucosal bleeding due to thrombocytopenia), hemophilia, liver diseases, certain microbial infections, and chemical poisoning.

What are the characteristics of skin purpura in allergic purpura patients?

1. The skin manifestations vary, often appearing as purpura and erythema of different sizes. They may be raised, initially itchy or painful, and can merge into patches.
2. The purpura starts as deep red, does not fade under pressure, and may merge into patches. Over days, it gradually turns dark red and then brown, usually fading within 1–2 weeks.
3. Purpura is more common on the limbs than the trunk, primarily on the extensor surfaces of the lower limb joints and buttocks, often symmetrically distributed and recurring in batches^[2,4].

How is allergic purpura classified?

Based on clinical manifestations, allergic purpura is divided into six types^[2,4]:

1. Simple allergic purpura (purpuric type): The most common type, mainly presenting as skin purpura, initially deep red and symmetrically distributed on the lower limbs and buttocks.
2. Abdominal allergic purpura: In addition to skin purpura, there are gastrointestinal symptoms and signs, such as abdominal pain, nausea, and vomiting.
3. Articular allergic purpura: Besides skin purpura, there are joint swelling, pain, and other symptoms.
4. Renal allergic purpura: A more severe condition, with symptoms like hematuria and proteinuria accompanying skin purpura.
5. Mixed allergic purpura: Skin purpura combined with two or more of the above manifestations.
6. Other allergic purpura: Rare cases may involve the eyes (e.g., iritis, eye pain, photophobia, retinal hemorrhage, blurred vision) or the brain (e.g., headache, seizures).

What are the common bleeding sites in allergic purpura?

Allergic purpura primarily affects capillaries, small arteries, and small veins throughout the body, causing vasculitis, which can lead to bleeding in any part of the body^[4].

Generally, common bleeding sites in allergic purpura patients include the skin of the lower limbs and buttocks, gastrointestinal tract, joints, and kidneys^[2].

In rare cases, it may involve the eyes, brain, or meningeal vessels, leading to optic atrophy, iritis, retinal hemorrhage, edema, headaches, and other central nervous system symptoms^[2].

Why does allergic purpura cause abdominal pain by affecting the gastrointestinal tract?

Because the capillaries in the digestive tract mucosa and visceral peritoneum are affected, patients may experience abdominal pain, often occurring alongside purpura or occasionally preceding it, which can be misdiagnosed as a surgical acute abdomen^[2,4].

Abdominal pain typically presents as paroxysmal colic, mostly around the navel or lower abdomen, with possible abdominal rigidity (hardness upon touch) and tenderness^[4].

Why does allergic purpura cause joint pain?

Due to vascular involvement in the joints, allergic purpura may also cause joint swelling, pain, tenderness, and dysfunction (e.g., difficulty squatting or climbing stairs), which can lead to misdiagnosis as osteoarthritis, especially in elderly patients^[2].

Joint involvement often occurs in large joints like the knees, ankles, elbows, and wrists, with recurrent, migratory pain (i.e., pain shifts locations). It usually resolves within days without causing joint deformities^[4]. Many patients may not even notice it.

Why does allergic purpura affect the kidneys?

Due to inflammatory reactions in the glomerular capillaries, patients may develop kidney issues, such as hematuria (microscopic or visible red, meat-wash-colored urine), proteinuria (protein in urine), and occasionally edema and hypertension^[2].

About one-third of patients experience kidney involvement. Kidney damage typically occurs 1–2 weeks after purpura appears but may be delayed (2–4 weeks). Over half recover within 3–4 weeks, while a few may develop chronic glomerulonephritis or nephrotic syndrome due to recurrent purpura and hematuria^[2,4].

CAUSES

Does thrombocytopenia cause skin purpura?

Abnormal platelets are just one of the factors. There are three fundamental causes of skin purpura (reddish-purple skin changes caused by bleeding under the skin and mucous membranes): abnormal blood vessel wall function, abnormal platelet count or function, and coagulation dysfunction^[3]. Any abnormality in these three aspects can lead to skin and mucosal bleeding.

1. Abnormal blood vessel wall function: Normally, when blood vessels are damaged, local small blood vessels contract to stop bleeding. If the capillary walls have congenital defects (e.g., hereditary hemorrhagic telangiectasia) or are damaged (e.g., by bacterial or viral infections), they cannot contract to stop bleeding, leading to skin purpura.
2. Abnormal platelets: At the site of vascular injury, platelets adhere to each other, aggregate to block the wound, and cause strong vasoconstriction to promote local hemostasis. When the quantity or quality of platelets is abnormal, skin purpura can occur.
3. Abnormal coagulation function: The coagulation process requires the participation of clotting factors. A deficiency or dysfunction of clotting factors (e.g., hemophilia) can lead to coagulation disorders, resulting in skin purpura.

Blood vessel wall function, platelet function, and coagulation function work together to prevent bleeding in the body.

What is the pathogenesis of Henoch-Schönlein purpura?

The pathogenesis of Henoch-Schönlein purpura (HSP) is not fully understood. Although the disease is an immune-mediated vasculitis associated with IgA deposition, how IgA participates and functions remains unclear^[1,2].

It is generally believed that when genetically predisposed individuals are exposed to certain factors, their bodies produce abnormal reactions, leading to systemic vasculitis, i.e., HSP^[2]. Related factors include:

1. Infections
   • Bacterial: Respiratory infections are most common, primarily β-hemolytic streptococcus.
   • Viral: Often seen in eruptive viral infections, such as measles and chickenpox.
   • Others: Parasitic infections, mainly roundworms.
2. Food
   Mainly protein-based foods that cause allergies, such as fish, shrimp, eggs, and milk.
3. Medications
   • Antibiotics: Such as penicillin and cephalosporins (e.g., cefradine).
   • Antipyretic analgesics: Such as phenylbutazone and indomethacin.
   • Other drugs: Such as atropine and isoniazid.
   • Others: Such as pollen, dust, and vaccinations.

Which populations are more prone to Henoch-Schönlein purpura?

HSP is more common in males and can occur at any age, but it primarily affects children aged 3–15, with a peak incidence between 4–8 years^[1,5].

Foreign studies have shown that HSP is associated with "familial Mediterranean fever" (FMF), and the incidence of HSP is higher in FMF populations^[1].

Is Henoch-Schönlein purpura an allergy?

HSP is not an allergy. The two have fundamental differences.

An allergy refers to the body's abnormal reaction to common substances (allergens) such as pollen, dust, or food. After exposure to allergens, the body produces IgE antibodies, leading to the release of histamine (an inflammatory mediator), which causes allergic symptoms such as rashes, sneezing, and itching^[6].

HSP is an immune-mediated vasculitis associated with IgA deposition^[1], without the involvement of "allergy." In 2012, an international consensus renamed HSP as IgA vasculitis to better reflect its pathophysiological characteristics. Although "Henoch-Schönlein purpura" is an older term, it is still widely used^[7].

Although HSP is not an allergy, it can be triggered by allergic factors, such as certain foods like milk, eggs, and fish^[2].

DIAGNOSIS

How to distinguish purpura, petechiae, ecchymosis, and hematoma?

Purpura, petechiae, and ecchymosis are differentiated based on the diameter of subcutaneous bleeding and accompanying conditions^[3]:

1. Lesions smaller than 2 mm are called petechiae (or bleeding spots);
2. Lesions measuring 3–5 mm are called purpura;
3. Lesions larger than 5 mm are called ecchymosis;
4. Patchy bleeding with significant skin elevation is called a hematoma.

For smaller petechiae or purpura, differentiation from red rashes or cherry angiomas is necessary. Red rashes typically fade or disappear under pressure, whereas petechiae, purpura, and cherry angiomas do not. However, cherry angiomas may feel slightly raised and have a shiny surface.

What laboratory tests are needed for allergic purpura?

1. Platelet function and coagulation tests:

Allergic purpura is a hemorrhagic and coagulation disorder of the blood system, so platelet and coagulation function tests are essential. Typically, allergic purpura may show prolonged bleeding time, but platelet count, function, and coagulation are normal.

2. Urinalysis and renal function tests:

Renal-type allergic purpura or mixed types with renal involvement may exhibit varying degrees of renal impairment, such as hematuria, proteinuria, elevated blood urea nitrogen, or decreased creatinine clearance. Urinalysis and renal function tests are required.

3. Others:

Depending on symptoms (e.g., fever due to infection, defined as axillary temperature >37°C), tests like antinuclear antibodies, complement, and erythrocyte sedimentation rate may be needed to differentiate from other diseases and assess severity^[2,4].

How is allergic purpura diagnosed?

Allergic purpura is confirmed if all four criteria are met^[2,8]:

1. History of low-grade fever (axillary temperature 37–38°C), sore throat, fatigue, or upper respiratory infection 1–3 weeks before onset;
2. Typical purpuric skin lesions on limbs, possibly accompanied by abdominal pain, joint swelling, or hematuria;
3. Normal platelet count, function, and coagulation tests;
4. Exclusion of other causes of vasculitis or purpura, such as thrombocytopenic purpura, nephritis, or rheumatoid arthritis.

Is bone marrow aspiration necessary for diagnosing allergic purpura?

No. However, it may be required if other diseases causing purpura are suspected and diagnosis is difficult.

Bone marrow aspiration is a common diagnostic technique for collecting bone marrow fluid, primarily used for hematologic morphology testing. It is crucial for diagnosing leukocyte disorders (e.g., acute leukemia), erythrocyte disorders (e.g., anemia), and platelet disorders (e.g., thrombocytopenic purpura).

Allergic purpura is a hemorrhagic disease involving blood vessel walls, with typically normal leukocytes, erythrocytes, and platelets. Thus, bone marrow aspiration is unnecessary^[2].

TREATMENT

Which department should I go to for Henoch-Schönlein purpura?

Hematology or rheumatology and immunology. For children, pediatric departments may also be appropriate.

How is Henoch-Schönlein purpura treated?

Most patients recover spontaneously, so treatment mainly involves supportive care, including general measures, symptomatic treatment, anti-allergy therapy, and, if necessary, glucocorticoids, immunosuppressants, or anticoagulation therapy^[2,4,9]. Details are as follows:

1. General measures:
   • Eliminate potential triggers, such as avoiding allergenic medications (e.g., indomethacin, isoniazid) or foods (e.g., milk, fish);
   • Bed rest during acute episodes;
   • Elevate affected limbs or rest in bed if edema occurs in the lower limbs or buttocks.
2. Symptomatic treatment:
   • Fasting in cases of gastrointestinal bleeding;
   • For abdominal pain, antispasmodics like atropine or anisodamine may be used. Common side effects include constipation, dry mouth, and facial flushing;
   • Severe joint pain may be managed with NSAIDs like ibuprofen or naproxen. Common side effects include nausea and vomiting.
3. Anti-allergy therapy: Antihistamines such as promethazine, chlorpheniramine, or loratadine may be used. Common side effects include drowsiness, dry mouth, and fatigue.
4. Glucocorticoids (e.g., prednisone, methylprednisolone) are suitable for severe renal involvement or intolerable pain (affecting sleep), usually for no more than 30 days. Long-term or high-dose use (exceeding 30 days or 1–4 mg/kg/day)^[10] may cause facial swelling, osteoporosis, or gastrointestinal bleeding. Follow medical advice.
5. For refractory or recurrent cases, immunosuppressants (e.g., cyclosporine, azathioprine) or anticoagulants (e.g., heparin, warfarin) may be considered. Side effects include nausea, vomiting, or bleeding (e.g., gum or nosebleeds).

How long is the glucocorticoid treatment course for Henoch-Schönlein purpura?

Typically, methylprednisolone or prednisone is used for no more than 30 days^[4].

Glucocorticoids suppress inflammation, reduce exudation, and improve capillary permeability, making them effective for abdominal or joint pain.

What are the possible side effects of glucocorticoids in Henoch-Schönlein purpura patients?

Prednisone is commonly used^[2]. Potential side effects include:

1. Increased infection risk due to immune suppression;
2. High doses (1–4 mg/kg/day)^[10] may cause fluid retention and hypertension;
3. Long-term use (over 30 days)^[10] may lead to osteoporosis or avascular necrosis.

However, the low-dose, short-term regimen for Henoch-Schönlein purpura minimizes these risks.

What is the prognosis of Henoch-Schönlein purpura? Can it be cured?

Yes, it is curable.

The course typically lasts weeks to months. Most cases are self-limiting, but some may recur or persist for years.

Renal involvement may lead to chronic glomerulonephritis or nephrotic syndrome^[2].

Can Henoch-Schönlein purpura recur?

Recurrence occurs in 5%–30% of patients, but symptoms are usually milder than the initial episode^[5,9].

How is follow-up conducted for Henoch-Schönlein purpura?

Since renal complications may develop months after onset, regular urine tests and blood pressure monitoring are recommended.

During active symptoms, test urine and blood pressure every 1–2 weeks. After symptoms resolve, continue every 1–2 months for a year. Due to delayed renal risks, annual screening (urinalysis and blood pressure) is advised thereafter^[9].

DIET & LIFESTYLE

Can patients with allergic purpura eat fish, meat, eggs, milk, and other foods?

Allergic purpura may be triggered by certain foods, such as fish, chicken, eggs, and milk. During treatment, it is generally recommended to avoid consuming foods that may induce the condition^[2]. After treatment, follow the doctor's advice.

If the patient's allergic purpura was not caused by these foods, there is no need to deliberately restrict their diet.

What should patients with allergic purpura pay attention to?

1. Self-monitor for accompanying symptoms: Since allergic purpura can affect capillaries throughout the body, in addition to observing skin purpura, pay attention to symptoms and signs in other parts of the body, especially abdominal pain or joint pain. Monitor urine for hematuria and stool for blackening.
   • If red urine or hematuria is observed, it indicates kidney involvement, requiring prompt treatment.
   • If black stool is noticed, consult a doctor for occult blood testing to rule out gastrointestinal bleeding.
   • If abdominal pain occurs, be particularly alert for digestive system involvement.
2. Self-monitor changes in purpura: Since the rash of allergic purpura tends to recur and appear in batches, observe skin purpura daily to detect new lesions promptly. Recurring new purpura suggests incomplete disease control, possibly due to unresolved causes like underlying infections^[2,11].

What are the nursing and dietary precautions for patients with allergic purpura?

1. Maintain skin cleanliness, avoid friction, bruising, or injury to prevent aggravated bleeding and skin infections.
2. Monitor the absorption of skin purpura and watch for new lesions.
3. Observe changes in urine volume and color, especially if kidneys are affected. Symptoms may include red urine (hematuria), foamy urine (proteinuria), or reduced urine output^[2].
4. If abdominal involvement occurs, rest in bed and monitor stool color.
5. Diet should generally be nutritious, easily digestible, mild, and low-irritant. For gastrointestinal bleeding, provide low-residue semi-liquid (e.g., soft noodles, porridge) or liquid diets (e.g., broth, vegetable juice). Temporarily fast if severe hematemesis or bloody stool occurs. For kidney damage, adopt a low-salt diet (recommended 2–3 g/day, about half a bottle cap)^[11].

PREVENTION

How to Prevent Allergic Purpura?

The causes of allergic purpura are complex, and there is no highly effective prevention method.

1. If symptoms of allergic purpura occur after exposure to a specific substance (e.g., pollen, fish) or medication (e.g., indomethacin, isoniazid), avoid contact with it in daily life;
2. Additionally, maintain hygiene, wash hands before meals and after using the toilet, and prevent bacterial or viral infections, which can help with prevention^[11].