Responsa על נדה 31:2

The blood stains on the shirt and sheets of a leprous woman do not render her impure. For these stains came from her leprous skin rather than from her womb. A stain on her shirt does not render her impure even during her "period", if she examined herself.
SOURCES: L. 185; Tashbetz 481; Orhot Hayyim II, p. 126.