How come I have interstitial cystitis, but nobody else in the family has it?

Unknown. Interstitial cystitis (ic) also called painful bladder syndrome (pbs) is common but causes are unclear, & likely there are many different causes. Treatments include medication by mouth or instilled into bladder, neuromodulation (estim) or treatment of hypertonic (spastic) pelvic muscles with pt, medication or injections.