Is HSP Associated with Nephritis?
Yes, Henoch-Schönlein purpura (HSP) is definitively associated with nephritis, occurring in approximately 20-50% of children and representing a major determinant of long-term morbidity and mortality. 1, 2
Epidemiology and Clinical Significance
Renal involvement occurs in 40% of pediatric HSP cases, manifesting as hematuria and/or proteinuria, and represents the primary source of long-term morbidity rather than a separate complication. 3, 1
Adults with HSP have more severe renal involvement at presentation compared to children, with 32% showing renal insufficiency (creatinine clearance <50 ml/min) at diagnosis, typically associated with proteinuria (99%) and/or hematuria (93%). 4
The long-term prognosis of HSP is directly dependent on the severity of renal involvement, with HSP nephritis leading to chronic kidney disease in up to 20% of pediatric patients after 20 years of follow-up. 3, 5
Diagnostic Criteria for HSP with Nephritis
HSP nephritis is diagnosed when palpable purpura is present plus renal involvement (hematuria and/or proteinuria), with or without arthralgia/arthritis or abdominal pain. 1, 2
The classic triad of hematuria, purpuric lesions, and ankle pain is specifically diagnostic of HSP with renal involvement. 2
Urinalysis with microscopy is essential at every clinical visit to detect red blood cell casts and dysmorphic RBCs, which indicate glomerular involvement and help assess severity of glomerulonephritis. 2
Pathophysiology
HSP nephritis is characterized by IgA deposition in the glomerular mesangium, similar to IgA nephropathy, with increased serum IgA concentrations and IgA-containing circulating immune complexes in vessel walls. 3, 5
The disease involves abnormalities of IgA1 exclusively (not IgA2), possibly due to abnormal glycosylation of O-linked oligosaccharides unique to the hinge region of IgA1 molecules. 3
Endocapillary glomerulonephritis is the most frequent histologic lesion on renal biopsy (61% of cases), with crescentic glomerulonephritis representing the most severe form. 4
Prognosis and Outcomes
In adults, HSP nephritis has a poor prognosis: only 20% achieve clinical remission (absence of proteinuria, hematuria, and normal renal function), while 11% reach end-stage renal failure, 13% exhibit severe renal failure (CrCl <30 ml/min), and 14% develop moderate renal insufficiency (CrCl <50 ml/min). 4
Patient survival in adult HSP is only 74% at long-term follow-up, with the first cause of death being carcinoma (most commonly respiratory or digestive tract). 4
Prognostic factors for poor renal outcomes include: renal function impairment and proteinuria level at presentation, degree of interstitial fibrosis on biopsy, percentage of sclerotic glomeruli, and presence of glomeruli with fibrinoid necrosis. 4
Common Pitfalls
Failing to perform urinalysis at every clinical visit can lead to delayed detection of renal relapse or progression, as HSP nephritis can develop insidiously even after initial presentation. 1
Assuming HSP is always self-limited is dangerous—while one-third of patients have recurrences, the renal involvement can progress to end-stage renal disease, particularly in adults. 3, 4
Not recognizing that adults have worse outcomes than children may lead to inadequate monitoring; adults are more likely to have severe initial renal involvement with higher risk of progression. 6, 4