Objective: To assess the risk factors for developing Henoch-Schönlein purpura nephritis (HSN) and to determine the time period when renal involvement is unlikely after the initial disease onset.
Design: A prospective study of 223 paediatric patients to examine renal manifestations of Henoch-Schönlein purpura (HSP). The patient's condition was monitored with five outpatient visits to the research centre and urine dipstick testing at home.
Results: HSN occurred in 102/223 (46%) patients, consisting of isolated haematuria in 14%, isolated proteinuria in 9%, both haematuria and proteinuria in 56%, nephrotic-range proteinuria in 20% and nephrotic-nephritic syndrome in 1%. The patients who developed HSN were significantly older than those who did not (8.2±3.8 vs 6.2±3.0 years, p<0.001, CI for the difference 1.1 to 2.9). Nephritis occurred a mean of 14 days after HSP diagnosis, and within 1 month in the majority of cases. The risk of developing HSN after 2 months was 2%. Prednisone prophylaxis did not affect the timing of the appearance of nephritis. The risk factors for developing nephritis were age over 8 years at onset (OR 2.7, p=0.002, CI 1.4 to 5.1), abdominal pain (OR 2.1, p=0.017, CI 1.1 to 3.7) and recurrence of HSP disease (OR 3.1, p=0.002, CI 1.5 to 6.3). Patients with two or three risk factors developed nephritis in 63% and 87% of cases, respectively. Laboratory tests or blood pressure measurement at onset did not predict the occurrence of nephritis.
Conclusion: The authors recommend weekly home urine dipstick analyses for the first 2 months for patients with HSP. Patients with nephritis should be followed up for more than 6 months as well as the patients with HSP recurrence.