A 38-year-old man presented with numerous pink-yellow firm papules and nodules on the bilateral elbows for 10 years spreading to the hands and knees in the past year. What is your diagnosis?

中文翻译：

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中年男性慢性进行性粉黄色丘疹和结节

男性，38岁，双侧肘部出现大量粉黄色硬性丘疹、结节，已有10年，去年蔓延至手、膝。您的诊断是什么？