Henoch-Schönlein purpura, also referred to as anaphylactoid purpura is a systemic vasculitis syndrome characterized by palpable purpura (usually distributed over the buttocks and lower extremities), arthralgias, gastrointestinal signs and symptoms, and glomerulonephritis. It is a small vessel vasculitis.
Incidence And Prevalence
Henoch-Schönlein purpura is usually seen in children, age from 4 to 7 years; however, the disease may also be seen in infants and adults. It is not a rare disease, accounting for approximately 5 and 24 admissions per year at one pediatric hospital. The male to female ratio is 1.5:1. A seasonal variation with a peak incidence in spring has been noted.
Pathophysiology And Pathogenesis
The presumptive pathogenic mechanism for Henoch-Schönlein purpura is immune-complex deposition. A number of inciting antigens have been suggested including upper respiratory tract infections, foods, insect bites, and immunizations. IgA is the antibody class most often seen in the immune complexes and has been demonstrated in the renal biopsies of these patients.
Clinical And Laboratory Manifestations
In pediatric patients, presenting symptoms related to the skin, gut, and joints are present in 50 percent of cases. In adults, presenting symptoms related to the skin are seen in over 70 percent of patients, while initial complaints related to the gut or the joints are noted in fewer than 20 percent of cases. The typical palpable purpura is seen in virtually all patients; most patients develop polyarthralgias in the absence of frank arthritis. Gastrointestinal involvement, which is seen in almost 70 percent of pediatric patients, is characterized by colicky abdominal pain usually associated with nausea, vomiting, diarrhea, or constipation and is frequently accompanied by the passage of blood and mucus per rectum; bowel intussusception may occur rarely. The renal involvement is usually characterized by mild glomerulonephritis leading to proteinuria and microscopic hematuria, with red blood cell casts in the majority of patients; it usually resolves spontaneously without therapy. Rarely, a progressive glomerulonephritis will develop. Renal failure is the most common cause of death in the rare patient who dies of Henoch-Schönlein purpura. Although certain studies have found that renal disease is more severe in adults, this has not been a consistent finding. However, the course of renal disease in adults may be more insidious and thus requires close follow-up. Myocardial involvement can occur in adults but is rare in children.
Routine laboratory studies generally show a mild leukocytosis, a normal platelet count, and occasionally eosinophilia. Serum complement components are normal, and IgA levels are elevated in about one-half of patients.
The prognosis of Henoch-Schönlein purpura is excellent. Most patients recover completely, and some do not require therapy. Treatment is similar for adults and children. When glucocorticoid therapy is required, prednisone in doses of 1 mg/kg per day and tapered according to clinical response has been shown to be useful in decreasing tissue edema, arthralgias, and abdominal discomfort; however, it has not proven beneficial in the treatment of skin or renal disease and does not appear to shorten the duration of active disease or lessen the chance of recurrence. Patients with rapidly progressive glomerulonephritis have been anecdotally reported to benefit from intensive plasma exchange combined with immunosuppressive drugs.