Henoch-Schönlein purpura, now more commonly called IgA vasculitis, is a condition where tiny blood vessels throughout the body become swollen and irritated, often leading to a distinctive rash, joint pain, and sometimes affecting the kidneys and digestive system.
Understanding Henoch-Schönlein Purpura
Henoch-Schönlein purpura is a condition that causes inflammation in the smallest blood vessels in your body. This inflammation is called vasculitis, which simply means that blood vessels become swollen and irritated. When this happens, these tiny vessels can leak blood cells into surrounding tissues, causing a range of symptoms that can affect the skin, joints, stomach, and kidneys. The condition is also known as IgA vasculitis because it involves a specific protein called immunoglobulin A, or IgA for short, that deposits in the walls of blood vessels and triggers the inflammation.[1]
This condition has a long history in medicine. An English physician named William Heberden first described it in the early 1800s when he noticed a young boy who developed a rash along with joint pain and stomach problems. Later, two German doctors, Johann Schönlein and Eduard Henoch, added more observations about the condition, which is why it bears their names today. Despite being recognized for over two centuries, doctors still don’t fully understand what triggers Henoch-Schönlein purpura in every case.[3]
The good news is that Henoch-Schönlein purpura usually goes away on its own without causing lasting problems. Most people, especially children, recover completely within a few weeks or months. However, some cases can be more serious, particularly when the kidneys become involved, which is why close monitoring and follow-up care are essential parts of managing this condition.[1]
Who Gets Henoch-Schönlein Purpura?
Henoch-Schönlein purpura is the most common type of vasculitis in children. It affects roughly 10 to 22 people out of every 100,000 each year, though some sources suggest rates around 14 to 20 per 100,000 children specifically. The condition shows a clear preference for younger age groups, with more than 90 percent of cases occurring in children. The peak age for developing Henoch-Schönlein purpura is around five to six years old, though it can appear in children as young as two or as old as 10 to 15 years.[8][10]
Boys are affected more often than girls, with roughly twice as many boys developing the condition. While Henoch-Schönlein purpura can occur at any time of year, it appears more frequently during the late autumn, winter, and early spring months. This seasonal pattern suggests a connection to respiratory infections, which are more common during colder months.[2][8]
Although Henoch-Schönlein purpura is much more common in children, adults can develop it too. When adults get this condition, it tends to be more severe and lasts longer than in children. The average duration of skin symptoms in adults can extend to about 28 months, compared to just a few weeks in children. Adults also face a higher risk of developing serious kidney problems that could become permanent.[6]
The condition can run in families, as it sometimes affects siblings in the same household. Infants and very young children under two years of age tend to experience milder forms of the disease, while children between ages three and ten typically show the classic symptoms. In contrast, teenagers and adults often experience more prolonged illness and more severe complications.[5][9]
What Causes This Condition?
The exact cause of Henoch-Schönlein purpura remains unknown, but doctors have identified several factors that appear to trigger the condition. The body’s immune system, which normally protects against infections and diseases, mistakenly attacks its own blood vessels in what’s called an autoimmune response. This means the body’s natural defenses, which should only target harmful invaders like bacteria or viruses, instead turn against healthy tissues by mistake.[5][9]
In Henoch-Schönlein purpura, the immune system produces deposits of IgA protein in the walls of small blood vessels. These deposits cause the vessels to become inflamed and leak blood and fluid into surrounding tissues. When this happens in the skin, it creates the characteristic rash. When it occurs in the intestines, it can cause stomach pain and bleeding. If the kidneys are affected, blood and protein may appear in the urine.[8]
More than half of children with Henoch-Schönlein purpura develop the condition shortly after having an upper respiratory infection, such as a cold or sore throat. The symptoms of Henoch-Schönlein purpura typically appear about 10 days after the start of the respiratory infection. Several specific germs have been linked to triggering the condition, including Group A streptococcus bacteria, which causes strep throat. Viral infections such as parvovirus B19, Epstein-Barr virus, varicella (chickenpox), and adenovirus have also been associated with cases of Henoch-Schönlein purpura.[8][19]
Besides infections, other triggers have been reported. Some cases have occurred after vaccinations for diseases like typhoid, measles, cholera, and yellow fever, though this is rare. Food allergies, reactions to certain medications, insect bites, and exposure to cold weather have also been linked to the development of Henoch-Schönlein purpura in some individuals. However, in many cases, no clear trigger can be identified.[19]
Risk Factors
Several factors increase the likelihood of developing Henoch-Schönlein purpura. Age is the most significant risk factor, as the condition predominantly affects children between three and ten years old, with the highest risk around age five to six. Being male also increases risk, as boys develop the condition about twice as often as girls.[8]
Having a recent upper respiratory infection is a major risk factor. About 50 percent of children with Henoch-Schönlein purpura had a cold, sore throat, or other respiratory illness in the weeks before their symptoms began. This connection is so common that doctors often ask about recent illnesses when evaluating a child for possible Henoch-Schönlein purpura.[18][23]
The time of year also plays a role in risk. Cases are more common during late autumn, winter, and early spring, which aligns with the season when respiratory infections are most prevalent. This seasonal pattern provides further evidence of the link between infections and the development of Henoch-Schönlein purpura.[2]
There may be some genetic factors at play as well. The condition can occur in siblings from the same family, suggesting a possible hereditary component. However, no specific gene has been definitively linked to Henoch-Schönlein purpura. Some researchers continue to investigate whether certain genetic variations might make some people more susceptible to developing the condition after being exposed to a trigger like an infection.[5][20]
For adults, different factors seem to influence the severity of disease. Adults who develop Henoch-Schönlein purpura are more likely to experience complications, particularly permanent kidney damage. Pregnancy in women who have had Henoch-Schönlein purpura requires careful monitoring, as even mild kidney symptoms at the time of initial diagnosis can lead to problems during and after pregnancy.[13]
Common Symptoms
The symptoms of Henoch-Schönlein purpura can develop in any order and may appear gradually over several days or even weeks. This variability sometimes makes diagnosis challenging, as not all symptoms appear at once. The most recognizable symptom, a distinctive rash, occurs in all cases, but it may not be the first sign of illness. In fact, the rash is the presenting complaint in only about 75 percent of cases, with other symptoms sometimes appearing first.[18][23]
The hallmark rash of Henoch-Schönlein purpura is called purpura, which appears as small, raised spots that look like bruises. These spots start out red but can turn purple or rust-colored as they age. The distinctive feature of this rash is that it doesn’t fade or blanch when you press on it with a finger or a glass, unlike many other rashes that temporarily lighten with pressure. The spots are typically small, ranging from one to five millimeters, and may feel slightly raised or bumpy when you touch them.[1][4]
The rash appears most commonly on the legs and buttocks, particularly in areas where clothing creates pressure, such as sock lines or the waistband of pants. In younger children who are not yet walking, the rash may appear on the back and buttocks. In older children and adults who spend more time on their feet, the rash tends to concentrate on the lower legs and ankles. The rash can also spread to the arms, face, and trunk, though this is less common. In severe cases, the spots may blister or develop into larger, darker areas.[1][10]
Joint pain and swelling affect 50 to 75 percent of people with Henoch-Schönlein purpura. The pain typically involves the large joints, especially the knees and ankles, though the elbows, wrists, and hips can also be affected. The joints may become swollen, tender, and warm to the touch. Joint symptoms often appear about one to two weeks before the rash develops, which can initially lead doctors to consider other diagnoses such as arthritis. The good news is that this joint involvement doesn’t cause permanent damage or deformity, and the pain and swelling usually resolve when the condition goes away.[1][6]
Abdominal pain occurs in 50 to 65 percent of cases. The pain can range from mild discomfort to severe, cramping pain that may come and go. It typically starts after the rash appears, though sometimes it precedes the rash. The pain often comes with nausea and vomiting. In some cases, blood appears in the stool, either visible as red streaks or detectable only through laboratory tests. The intestinal involvement occurs because small blood vessels in the bowel wall become inflamed and leak blood into the digestive tract.[6][8]
Kidney involvement affects 25 to 50 percent of people with Henoch-Schönlein purpura. The kidney problems are usually mild and may produce no noticeable symptoms at all. Most often, kidney involvement is discovered only when routine urine tests reveal blood or protein in the urine. In some cases, the urine may appear pink or tea-colored due to blood, or foamy due to protein. High blood pressure can develop when the kidneys are affected. While most kidney problems resolve without lasting damage, about one to five percent of people develop chronic kidney disease that persists long-term.[6][8]
Swelling can occur in various parts of the body, particularly in younger children. The swelling, called edema, commonly affects the hands, feet, and scrotum in boys. It can also appear around the eyes, especially in infants and children who are not yet walking. This swelling is painful and is caused by fluid leaking from inflamed blood vessels into the surrounding tissues. Unlike the rash, the swelling is usually soft and doesn’t leave marks when pressed.[18][23]
In boys, scrotal swelling and pain can be a particularly distressing symptom. This occurs when blood vessels in the scrotum become inflamed, causing tenderness and swelling. Sometimes testicular pain can be severe enough to raise concerns about testicular torsion, a surgical emergency where the testicle twists on itself. Doctors need to carefully evaluate boys with scrotal pain to distinguish between these conditions.[18][23]
General symptoms such as fatigue, low-grade fever, headache, and loss of appetite are common in the early stages of Henoch-Schönlein purpura. These symptoms often accompany or follow the upper respiratory infection that frequently precedes the condition. Children may feel generally unwell and less active than usual.[8][10]
Prevention
Unfortunately, there is no known way to prevent Henoch-Schönlein purpura. Because the exact cause of the condition remains unclear and it appears to result from a combination of genetic susceptibility and environmental triggers, specific prevention strategies have not been identified. The condition seems to represent an unpredictable immune response that occurs in certain individuals after exposure to triggers like infections.[2]
However, general measures to prevent infections may help reduce the risk of developing Henoch-Schönlein purpura, since respiratory infections are common triggers. These measures include good hand hygiene, avoiding close contact with people who are sick, keeping vaccinations up to date, and practicing other habits that support overall immune health. Parents can teach children to wash their hands regularly, especially before eating and after being in public places, to reduce their exposure to respiratory viruses and bacteria.[8]
For children who have already had Henoch-Schönlein purpura, about one-third will experience a recurrence, meaning the condition comes back after initially going away. The good news is that recurrent episodes are usually milder and shorter than the first episode. However, recurrences can happen multiple times over the course of a year. There are no proven strategies to prevent these recurrences, though some doctors may recommend avoiding known triggers if any were identified during the initial episode.[12][26]
Close monitoring is an important part of managing Henoch-Schönlein purpura, though it’s not prevention in the traditional sense. Regular follow-up appointments allow doctors to catch any developing kidney problems early, when they are most treatable. Urine tests and blood pressure checks should continue for at least six months after symptoms resolve, and sometimes for a full year. Early detection of kidney involvement allows for prompt treatment that may prevent progression to more serious, permanent kidney damage.[2][25]
How the Body Changes: Pathophysiology
To understand what happens in Henoch-Schönlein purpura, it helps to know a bit about the immune system and blood vessels. The immune system normally protects the body by producing proteins called antibodies that recognize and attack harmful invaders like bacteria and viruses. One type of antibody is immunoglobulin A, or IgA. In Henoch-Schönlein purpura, something goes wrong with the immune system, causing IgA antibodies to form complexes that deposit in the walls of small blood vessels throughout the body.[3][8]
These IgA deposits trigger inflammation in the blood vessel walls, a process called vasculitis. When blood vessels become inflamed, their walls become damaged and leaky. This allows blood cells, fluid, and proteins to escape from the vessels into surrounding tissues. The specific changes that occur depend on where in the body the affected blood vessels are located.[8]
In the skin, when small blood vessels called capillaries and venules become inflamed and leak blood cells, the result is the characteristic purpuric rash. The spots appear red or purple because red blood cells have escaped into the skin tissue. As these cells break down over time, the spots may turn brownish before fading. The rash tends to appear in gravity-dependent areas like the legs and buttocks because blood pressure is higher in these vessels when a person is standing or sitting, which may make leakage more likely.[1]
In the joints, inflammation around the blood vessels causes fluid to accumulate in and around the joint space. This leads to swelling, pain, and stiffness. The inflammation affects the soft tissues surrounding the joints rather than the joint surfaces themselves, which is why Henoch-Schönlein purpura doesn’t cause permanent joint damage or deformity, unlike some forms of arthritis.[19]
In the gastrointestinal tract, inflamed blood vessels in the intestinal wall can leak blood into the bowel, causing bloody stools. The inflammation also causes swelling and increased fluid in the intestinal wall, which appears as thickening on medical imaging and can lead to abdominal pain. In severe cases, the inflamed, swollen intestinal wall can fold in on itself, creating a condition called intussusception, where one part of the intestine telescopes into another part. This is a serious complication that can block the intestines and requires urgent medical attention.[2][18]
In the kidneys, IgA deposits accumulate in the glomeruli, which are tiny filtering units responsible for cleaning the blood and producing urine. When these filters become inflamed, they allow blood cells and proteins to leak into the urine when they should normally be retained in the bloodstream. The kidney involvement in Henoch-Schönlein purpura is very similar to another condition called IgA nephropathy, and in fact, the two conditions share many features. The main difference is that Henoch-Schönlein purpura typically affects younger children and involves other organs besides the kidneys.[3][8]
The inflammation in Henoch-Schönlein purpura involves immune cells called neutrophils that accumulate around the affected blood vessels. When examined under a microscope, tissue samples show characteristic changes called leukocytoclastic vasculitis, where fragments of damaged neutrophils can be seen. The presence of IgA deposits in the vessel walls, detected through a special technique called immunofluorescence, is what distinguishes Henoch-Schönlein purpura from other types of vasculitis.[10]
In most cases, the inflammatory process is self-limited, meaning it naturally resolves on its own over several weeks to months. The body gradually clears the IgA deposits and repairs the damaged blood vessels. This is why most children recover completely without long-term problems. However, in some cases, particularly in the kidneys, the inflammation can be more severe or prolonged, leading to scarring and permanent damage that persists even after the active inflammation has resolved.[8]
