Chlamydia pneumonia, trachoma, and/or psittacosis, independently or as co-infections, can cause fibromyalgia. Chlamydia species infect endothelium, smooth muscles, and microglia, which generates increased TNF-alpha and cytokines. PCR levels for chlamydia pneumonia are higher in patients with fibromyalgia AND chronic fatigue.

Chlamydia species deplete energy in the cell, impair oxygen transport across the cell wall, and trigger inflammation—which matches the cellular findings in fibromyalgia.