Skoptic syndrome involves a person being fixated with or engaging in damaging their own genitals, to hefty extremes: it may include complete removal of their genitals (the penis or clitoris/vulva). It is classified as a type of gender dysphoria in the Diagnostic and Statistical Manual of Mental Disorders (DSM).
Why would someone want to cut off their own genitals?
This, being a Gender Identity Disorder Not Otherwise Specified, is not known, however some reasons offered by psychologists are sexual guilt, for example, where the genitals become the source of guilty sexual desire. Lopping them off seems a wise choice, since they appear to the person to be the source of the problem.
This topic is extremely varied, and depends heavily on the individual’s personal history and psychological profile. Another problematic disorder is body dysmorphia whereby the person has a desire to be a eunuch or to castrate themselves for any number of reasons, including sexual arousal. Apotemnophilia is whereby someone fantasises about being an amputee.