Illness-related causes of skin lesions. Skin lesions may be caused by another illness including: Bacterial infection, such as scarlet fever, or meningococcal meningitis, a serious condition caused by group A Streptococcus, can cause a skin rash.kin lesions may be caused by another illness including: Bacterial infection, such as scarlet fever, or meningococcal meningitis, a serious condition caused by group A Streptococcus, can cause a skin rash.