Aims To identify the presence and geographical distribution of mast cell (MC) subtypes: MC_T (tryptase positive–chymase negative) and MC_TC (tryptase positive–chymase positive) in bladder tissue.

Methods Bladder tissue was obtained from patients with painful bladder syndrome/interstitial cystitis (n=14) and normal histology from University Hospital Southampton tissue bank. Sequential tissue slices were immunohistochemically stained for MC subtypes using anti-MC tryptase (for MC_T and MC_TC) and anti-MC chymase (for MC_TC). Stained sections were photographed, and positively stained MCs were quantified using ImageJ. Data were analysed using descriptive statistics and individual paired t-tests.

Results There was a significant difference in the density of MCs between each layer of the disease bladder, with the greatest accumulation within the detrusor (p<0.001). There was a significant increase in MC_TC subtype in the lamina (p=0.009) in painful bladder syndrome/interstitial cystitis.

Conclusions Our results suggest that mastocytosis is present within all layers of disease bladder, especially the muscle layer. The varying increase in MC subtypes in the lamina and mucosa may explain the variability in painful bladder syndrome/interstitial cystitis symptoms. A high influx of MC_TC in the mucosa of individuals who also had ulceration noted within their diagnostic notes may be of the Hunner’s ulcer subclassification. These findings suggest a relationship between the pathogenesis of MC subtypes and the clinical presentation of painful bladder syndrome/interstitial cystitis. A cohort study would further elucidate the diagnostic and/or therapeutic potential of MCs in patients with painful bladder syndrome/interstitial cystitis.