Prognostic implications of normal or minimal urinary findings on long-term renal impairment in adults with Henoch-Schönlein purpura.

Background: Renal involvement in adult Henoch-Schönlein purpura is a major cause of morbidity and can lead to significant long-term renal impairment. The prognostic significance of normal or minimal urinary abnormalities at diagnosis is unknown.

Objective: To assess the risk of long-term renal impairment in patients with Henoch-Schönlein purpura who present with normal or minimal urinary abnormalities.

Methods: Retrospective cohort study of adult Henoch-Schönlein purpura patients presenting with normal urinalysis results, microscopic hematuria, or low-grade proteinuria. Patients were followed for development of long-term renal impairment, with adjusting for comorbidities.

Results: Forty-seven patients were included, with median follow-up 73.9 months (interquartile range 35 to 98 months). Thirty-nine patients (83.0%) had abnormal urinalysis results, of whom 15 (38.5%) progressed to long-term renal impairment. In contrast, 8 patients (17%) had normal urinalysis results, of whom only 1 (12.5%) developed long-term renal impairment (adjusted hazard ratio 10.58; 95% confidence interval 1.18-94.73). Renal events occurred at a median 36.1 months (interquartile range 17.1 to 61 months) from diagnosis, earlier in patients with comorbidities compared with those with none, and in a constant event rate over time.

Limitations: Small sample size.

Conclusions: Microscopic hematuria and low-grade proteinuria at Henoch-Schönlein purpura diagnosis is a poor prognostic sign for the development of long-term renal impairment. This population should be targeted for prolonged surveillance.