Which organism is associated with interstitial keratitis as an ocular manifestation?

• A. Mycobacteria
• B. Neisseria gonorrhoeae
• C. Treponema pallidum
• D. Chlamydia trachomatis

Answer: (C)

Interstitial keratitis is a form of corneal stromal inflammation driven by immune responses to certain infections, and it is classically linked to syphilis. Treponema pallidum, the syphilis-causing organism, can affect the eye in congenital or late syphilis, leading to stromal inflammation of the cornea with haze, vascularization, and scarring. That connection makes Treponema pallidum the best answer for this ocular manifestation.

Other organisms tend to cause different patterns: Neisseria gonorrhoeae usually produces a hyperacute purulent conjunctivitis with rapid corneal involvement rather than a chronic, interstitial keratitis; Chlamydia trachomatis causes inclusion conjunctivitis or trachoma with follicular conjunctivitis and pannus, not the classic interstitial keratitis; Mycobacteria can cause keratitis, but the characteristic stromal interstitial keratitis is most classically associated with syphilis.