A 7-year-old boy presented with multiple keratotic papules and blackhead-like papules on his hands and feet, and inner aspect of his left knee joint.

• 因手足和左膝关节内侧角化性丘疹和黑头粉刺样丘疹7年就诊。部分丘疹呈线状或带状排列(主要位于手足侧缘)。