The organism may accumulate in perivascular spaces of nearly any organ, including the central nervous system (CNS). It is unclear why some patients develop CNS infection and others do not. Rarely, organisms may invade any structures of the eye (such as cornea, anterior chamber, vitreous and choroid, and optic nerve) and cause local inflammation and edema. In primary or secondary syphilis, invasion of the meninges may result in lymphocytic and plasma cell infiltration of perivascular spaces (Virchow-Robin spaces). The extension of cellular immune response to the brainstem and spinal cord causes inflammation and necrosis of small meningeal vessels.In tertiary syphilis, reactivation of chronic latent infection may result in meningovascular syphilis, arising from endarteritis obliterans of small, medium, or large arteries supplying the CNS. The parenchymal syphilis, presents as tabes dorsalis and general paresis. Tabes dorsalis thought to be due to irreversible degeneration of nerve fibers in posterior columns of the spinal cord involving the lumbosacral and lower thoracic levels. The general paresis is caused by meningeal vascular inflammation and ependymal granulomatous infiltration may lead to neuronal loss, along with astrocytic and microglial proliferation and damage may preferentially occur in the cerebral cortex, striatum, hypothalamus, and meninges.Concurrent infection of T. pallidum with human immunodeficiency virus (HIV) has been found to affect the course of syphilis. Syphilis can lie dormant for 10 to 20 years before progressing to neurosyphilis, but HIV may accelerate the rate of the progress. Also, infection with HIV has been found to cause penicillin therapy to fail more often.
Acute zonal occult outer retinopathy (AZOOR) is an inflammatory retinopathy in the category of white dot syndromes typified by acute loss of one or more zones of outer retinal function associated with photopsia, minimal funduscopic changes and abnormal electroretinography findings.This retinal disease was first described by Donald Gass in 1992. Relatively little is known about the condition. Risk factors
Caucasian females in their mid-thirties appear to be most susceptible but the disease may affect anyone regardless of age, sex or race. Pathophysiology
The disease mechanism is unknown but it is believed that it may be caused by a virus, or an auto immune response. References


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