A 16-year-old boy presented with a changing skin lesion on his right lower back. The patient reported the presence of a stable red lesion since he was 7 years old; however, over the preceding month, this lesion developed new black spots within it. There was no associated pain, pruritus, or bleeding. His family history was notable for dysplastic nevus syndrome in his father and melanoma in a paternal uncle and cousin.

On examination of the right lower back, there was a cluster of 1-mm flat purple-black papules coalescing into a 1.5 × 1.0-cm oval plaque with surrounding erythema (Figure, A). On reinspection of the lesion at a subsequent visit, the morphology had significantly changed; there were 1-mm skin-colored to pink thin-walled vesicles clustered within a 1.5 × 1.0-cm oval telangiectatic plaque (Figure, B).

一个16岁男孩的右下背部皮肤病变不断。该患者报告说，自他7岁起就存在稳定的红色病变。但是，在过去的一个月中，该病灶内部出现了新的黑点。没有相关的疼痛，瘙痒或出血。他的家族病史在父亲中表现为增生性痣综合症，在父亲的叔叔和堂兄中则表现出黑色素瘤。

在检查右下背部时，有一簇1毫米的扁平紫黑色丘疹聚结成1.5×1.0厘米的椭圆形斑块，周围有红斑（图A）。在随后的探访中对病灶进行重新检查后，形态发生了明显变化。在1.5×1.0-cm椭圆形毛细血管扩张斑块内聚集着1毫米皮肤色至粉红色的薄壁囊泡（图B）。