Isolated hematuria and sterile pyuria may indicate systemic lupus erythematosus activity.

OBJECTIVE: To identify patients presenting with isolated hematuria and/or pyuria in the absence of other systemic lupus erythematosus (SLE) disease activity, describe their demographics, and determine whether they present with evidence of SLE flare in a period adjacent to the presentation. METHODS: We studied patients followed at the University of Toronto Lupus Clinic between 1970 and 2012. An episode of isolated hematuria (> 5 red blood cells per high power field) and/or pyuria (> 5 white blood cells per high power field) was defined as 2 consecutive visits with these findings in the absence of other concurrent SLE manifestations such as proteinuria, casts, or azotemia. We then excluded patients whose findings might be explained by urinary tract infections, menstruation, urolithiasis, and/or anticoagulation. Only patients presenting with no other SLE disease activity were included. RESULTS: Isolated hematuria and/or pyuria were identified in 49 patients, of whom 17 were excluded according to the criteria above, leaving 32. Twenty-four patients had another renal manifestation 1 year before and/or after the occurrence; 27 had a non-renal manifestation 1 year before and/or after the occurrence; 3 patients had a biopsy in the same time frame, all with evidence of active lupus nephritis. Therefore the majority of patients with an occurrence of isolated hematuria and/or pyuria had evidence of renal or other non-renal SLE disease activity at a time adjacent to this presentation. CONCLUSION: Although not proven, our results suggest that these manifestations were associated with SLE activity, either before or after the episode, and therefore may represent a phase of active disease.