Polyomavirus BK--a potential new therapeutic target for painful bladder syndrome/interstitial cystitis?

AIMS To investigate the role of urinary BK polyoma virus (BKPyV) in the pathophysiology and prognosis of patients with painful bladder syndrome/interstitial cystitis (PBS/IC). METHODS Urine samples were collected from 15 patients with PBS/IC and 8 control patients (with urolithiasis, overactive bladder and benign prostatic hyperplasia). BKPyV titres were quantitatively determined using real time PCR. Fisher's exact test was used to compare virus titre levels between the two groups. The PBS/IC patients subsequently underwent cystoscopy, hydrodistension and bladder biopsy. Finally, a chart review was performed in order to correlate PBS/IC subtype and treatment outcomes with BKPyV status. RESULTS Positive BKPyV titres were found in 11 out of 15 PBS/IC patients but none of the controls. Cystoscopy was performed in 13 of the 15 PBS/IC patients (in 2 BKPyV positive patients, cystoscopy was not performed). Bladder ulceration and glomerulations were observed in all 9 BKPyV positive PBS/IC patients but only 1 out of 4 BKPyV negative patients. None of the non-ulcerative PBS/IC patients had BKPyV positive urine. Viral titres were not predictive of the clinical course however, 3 patients with the highest viral titres eventually underwent cystectomy. CONCLUSIONS We identified BKPyV in the urine of virtually all our patients with ulcerative PBS/IC. This finding suggests there may be a pathophysiological association between the virus and the haemorrhagic manifestations of PBS/IC. Classifying PBS/IC patients into BKPyV positive or negative groups may prove useful in future research on markers of disease prognosis and the subtypes of PBS/IC. We believe that BKPyV may therefore have a role as a potential therapeutic target in PBS/IC.