Pediatirc Nephrology/ Henoch-Schönlein Purpura

ETIOLOGY
Henoch-Schönlein purpura (HSP) is a vasculitis of unknown etiology characterized by inflammation of small blood vessels with leukocytic infiltration of tissue, hemorrhage, and ischemia. The immune complexes associated with HSP are predominantly composed of IgA

EPIDEMIOLOGY

It occurs primarily in children 3 to 15 years of age, although it has been described in adults. HSP is slightly more common in boys than girls and occurs more frequently in the winter than the summer months

CLINICAL MANIFESTATIONS

HSP is characterized by rash, arthritis, and, less frequently, gastrointestinal or renal vasculitis. The hallmark of HSP is palpable purpura, caused by small vessel inflammation in the skin leading to extravasation of blood into the surrounding tissues. IgA often is deposited in the lesions. Although the rash can occur anywhere on the body, it is classically, below the waist on the buttocks and lower extremities

Arthritis occurs in 80% of patients with HSP; it can occur in any joint but tends to affect the lower extremities, most commonly the ankles and knees. The arthritis is acute and can be very painful with refusal to bear weight.

Gastrointestinal involvement occurs in about one half of affected children and most typically presents as mild to moderate crampy abdominal pain, thought to be due to small vessel involvement of the gastrointestinal tract leading to ischemia. Less commonly, significant abdominal distention, bloody diarrhea, intussusception, or abdominal perforation occurs and requires emergent intervention.

Gastrointestinal involvement is typically seen during the acute phase of the illness. It may precede the onset of rash.

One third of children with HSP develop renal involvement, which can be acute or chronic. Although renal involvement is mild in most cases, acute glomerulonephritis manifested by hematuria, hypertension, or acute renal failure can occur. Most cases of glomerulonephritis occur within the first few months of presentation, but rarely patients develop late renal disease, which ultimately can lead to chronic renal disease, including renal failure

LABORATORY AND IMAGING STUDIES

Erythrocyte sedimentation rate, C-reactive protein, and white blood cell count are elevated in patients with HSP. The platelet count is the most important test, because HSP is characterized by nonthrombocytopenic purpura with a normal, or even high, platelet count, differentiating HSP from other causes of purpura that are associated with thrombocytopenia

A urinalysis screens for evidence of hematuria. A serum blood urea nitrogen and creatinine should be obtained to evaluate renal function. Testing the stool for blood may identify evidence of gut ischemia. Any question of gut perforation requires radiologic investigation.

TREATMENT

Therapy for HSP is supportive. A short-term course of nonsteroidal anti-inflammatory drugs can be administered for the acute arthritis. Systemic corticosteroids usually are reserved for children with gastrointestinal disease and provide significant relief of abdominal pain. Renal manifestation may require in addition immunosuppresive therapy

PROGNOSIS

The prognosis of HSP is excellent. Most children have complete resolution of the illness without any significant sequelae. Patients with HSP renal disease (elevated blood urea nitrogen, persistent high-grade proteinuria) are at highest risk for long-term complications, such as hypertension or renal insufficiency, particularly if the initial course was marked by significant nephritis.

There is a long-term risk of progression to end-stage renal disease in less than 1% of children with HSP. The rare patients who develop end-stage renal disease may require renal transplantation. HSP may recur in the transplanted kidney.