Overlap of fibromyalgia with other medical conditions.

Fibromyalgia is a multisystem illness. One of its defining features, generalized pain, may also be present in other rheumatic entities. The diagnosis of fibromyalgia is not easy by any means, it requires a profound knowledge of internal medicine. This article discusses the different rheumatic and nonrheumatic diseases that overlap or are prone to be confused with fibromyalgia. It emphasizes the key points in the differential diagnosis.