Platelet-rich Plasma Intradermal Injection Combined With 308 nm Excimer Light for Treating Stable Acral Vitiligo

The goal of this clinical trial is to learn if platelet-rich plasma (PRP) works to treat acral stable vitiligo in adults. It will also learn about the safety of platelet-rich plasma. The main questions it aims to answer are: * Does PRP combined with 308 nm excimer phototherapy improve the efficacy compared to 308 nm excimer light alone in the treatment of vitiligo of the extremities? * What medical problems do participants have when taking PRP intradermal injections? Researchers will compare PRP to a placebo (a look-alike substance that contains no drug) to see if PRP works to treat acral vitiligo. Participants will: * Receive PRP intradermal injections once a month and 308 nm excimer phototherapy twice a week, or the same frequency of saline injections and phototherapy for 6 consecutive months * Visit the clinic once every 1 month for evaluations * Keep a diary of their symptoms or side effects during follow-up