Final answer:
Transgenderism involves a discrepancy between one's gender identity and assigned birth sex, often leading to gender dysphoria, while transvestic fetishism involves cross-dressing for sexual gratification without dissatisfaction regarding one's gender.
Step-by-step explanation:
The characteristic that differentiates transgenderism from transvestic fetishism is that clients diagnosed with transgenderism are dissatisfied with their gender, whereas clients diagnosed with transvestic fetishism are not. This means that individuals with transgenderism have a gender identity that does not align with their sex assigned at birth and may experience gender dysphoria. They might seek to transition to their identified gender through social, legal, or medical steps. In contrast, transvestic fetishism is specifically related to cross-dressing and is generally a behavior for sexual pleasure or gratification, without an underlying dissatisfaction with one's assigned gender.