We have encounted two patients with fibromyalgia (FM) initially diagnosed as having autoimmune fatigue syndrome (AIFS). To investigate the relationship between AIFS and FM, the distribution of the tender points in patients with AIFS was assessed according to the ACR criteria for FM. It was revealed that AIFS patients had 5.6 tender points on averages. Patients with headaches, digestive problems, or difficulty going to school had more tender points than patients without. Patients with ANA titers<1: 160 had more tender points than patients with ANA≥1: 160. Anti-Sa negative patients had more tender points than positive patients. These results suggest a relationship between AIFS and FM in terms of the pathophysiologic mechanisms of the numerous tender points. In other words, ANA-positive FM patients could be one form of AIFS, as well as ANA-positive chronic fatigue syndrome patients. Thus, autoimmunity could explain the controversial disease entities of FM and/or CFS. (J Nippon Med Sch 1999; 66: 239-244)
