Henoch-Schonlein purpura (HSP), also called immunoglobulin A vasculitis (IgAV), is a vascular disease that primarily affects small blood vessels. The disease is characterized by abnormal deposits of immunoglobulin A (an antibody) in the blood vessels, leading to their inflammation (vasculitis). The small vessels of the skin, joints, kidneys, and digestive organs are particularly involved. Signs and symptoms usually begin suddenly (and progress over days) and may include purple-colored spots on the skin (purpura); joint pain; and gastrointestinal problems such as abdominal pain, nausea, bloody stools, and rarely, severe complications requiring surgery. People with HSP may also develop glomerulonephritis (injury to the kidneys caused by inflammation) and poor kidney function, which may result in swelling of parts of the body or face (edema), and blood and protein in the urine (hematuria and proteinuria). Most cases of HSP occur in children and go away without causing serious or long-term health problems. Less commonly, the disease affects adults and may be more severe, leading to chronic kidney disease and kidney failure. The cause of HSP is not completely understood, but research indicates that genes (especially those involved in regulating the immune system) may play a key role in predisposing a person to HSP, as well as its severity. However, while genes may increase the risk of developing the disease (and in some cases more than one family member has HSP), the disease itself is not inherited. Environmental “triggers” such as foods, infections, or medications may also play a role in the onset of the disease. The diagnosis of HSP may be made based on symptoms, blood and urine tests, imaging studies, and/or a biopsy of the skin or kidney. Most cases go away within several weeks without treatment. When needed, treatment aims to relieve symptoms and may include medications for pain and inflammation. People with chronic kidney involvement or advanced kidney disease may require immunosuppressive medications, hemodialysis, or kidney transplantation. The long-term outlook depends on the extent of kidney involvement. Rarely, HSP is fatal due to kidney complications. In some cases, the disease recurs, sometimes more than once.

The cause of Henoch-Schonlein purpura (HSP) is not completely understood, but research indicates that genes play a key role in predisposing a person to developing HSP, as well as the severity of HSP in each person. The disease has been most strongly associated with having certain variations of genes in the human leukocyte antigen (HLA) gene family, a cluster of genes that the immune system uses to tell the difference between the body's own substances and foreign invaders. Environmental factors such as recent bacterial or viral infections, food allergies, and medication reactions also may play a role in the onset of HSP in people who are genetically predisposed.

The vast majority of people with Henoch-Schonlein purpura (HSP) recover on their own within several weeks. Supportive care until recovery when there is little or no kidney involvement may include adequate hydration, rest, and over-the-counter pain medication as needed for joint and abdominal pain due to inflammation. Swelling of the lower body may improve with bed rest or elevating the affected area of the body. If symptoms of inflammation are severe, prescription pain or anti-inflammatory medication may be needed. Non-steroidal anti-inflammatory drugs (NSAIDs) should not be used in people with impaired kidney function or kidney disease. Rarely, severe gastrointestinal complications require surgery. The use of glucocorticoids (steroids) in people with HSP has been under debate. While glucocorticoids have been reported to improve symptoms (particularly gastrointestinal symptoms), it is questionable whether they improve the course of the disease, and they may have potentially dangerous side effects (such as masking signs of fever and pain). They generally are not recommended as a means of preventing kidney or gastrointestinal complications. Hospitalization may be needed for those with dehydration, debilitating abdominal or joint pain (limiting the ability to move around), significant gastrointestinal bleeding, or kidney disease. People with significant kidney involvement or advanced kidney disease may require immunosuppressive medications, hemodialysis, or kidney transplantation. While immunosuppressive therapies such as rituximab have shown promising results in initial studies, more studies are needed to determine their safety and effectiveness in people with HSP who have severe kidney involvement and other severe symptoms.