Is Diet Coke suggested in autoimmune diseased patients?

No. There is no evidence from any reliable source, of any correlation, much less any causation, between diet sodas and any autoimmune disease. There are, of course, rumors, hoaxes and slanders attached to just about everything.

On their web site, the Lupus Foundation of America has posted:

We are aware there is an email message circulating on the Internet warning individuals with lupus about dangers associated with using the artificial sweetener aspartame. The Lupus Foundation of America consulted with the chair of the LFA Medical Council, Evelyn Hess, MD, MACP, MACR. Dr. Hess is one of the nation's leading researchers in the field of lupus specializing in environmental influences. According to Dr. Hess, there is, as of now, no specific proof of an association with aspartame as a cause or worsening of SLE.

People with lupus should always consult with their physician before making any changes in their medical treatment, diet, exercise or other routine based on information received via the Internet or other sources lacking known credentials.

Unfortunately, the hoax e-mail has been picked up by a writer at the Livestrong Foundation and used as the basis for a fear-mongering article, which is devoid of facts.