pityriasis nigra

例句：

1. 1. The patient had a pityriasis nigra on his back.
   患者背部有一块黑斑病。
2. 2. Pityriasis nigra is a common skincondition that can be treated with creamsand ointments.
   黑斑病是一种常见的皮肤病，可以通过药膏和油膏治疗。
3. 3. The doctor prescribed a special cream forthe patient's pityriasisnigra.
   医生为患者的黑斑病开了一种特殊的药膏。