Final answer:
The 3rd line of treatment for SLE dermatitis involves systemic immunosuppressive medications such as methotrexate, mycophenolate mofetil, or azathioprine.
Step-by-step explanation:
The 3rd line of treatment for systemic lupus erythematosus (SLE) dermatitis depends on the severity of symptoms and the individual patient's response to previous treatments. It is important to note that treatment plans are personalized and may vary for each individual. However, in general, the 3rd line of treatment may involve the use of systemic immunosuppressive medications such as methotrexate, mycophenolate mofetil, or azathioprine.