Contributor: Gordon K. Klintworth
Trachoma is an acute, infectious, cicatrizing keratoconjunctivitis caused by Chlamydia trachomatis. A cellular infiltrate consisting mainly of lymphocytes accumulates in the conjunctiva. It is characteristically associated with follicles that develop necrotic germinal centers. The conjunctival epithelium contains glycogen-rich intracytoplasmic inclusion bodies and Leber cells are also present. Eventually trachomatous pannus develops. The conjunctiva and eyelids become scarred and the scarring distorts the eyelids and causes ectropion. The conjunctivitis is commonly complicated by a secondary bacterial infection.
Spontaneous healing is common in children, but in adults the disease progresses more rapidly and rarely heals in the absence of treatment. Both eyes are almost always involved the upper half of the conjunctiva is affected more extensively than the lower. The trachomatous pannus impairs vision.
Trachoma, the leading cause of blindness in many developing countries is produced by Chlamydia trachomatosis serovars A, B, Ba and C. The disease is most prevalent in dry regions where poor personal hygiene, filth, inadequate public sanitation and countless flies are features of the environment. Infection is spread by several routes including direct contact, fomites, flies and contaminated fingers or water. After reproducing within the conjunctival epithelium, Chlamydia trachomatis elicits a mixed acute and chronic inflammatory cell infiltrate. Lymphoid aggregates and macrophages accumulate in the conjunctival stroma. This chronic infection causes progressive scarring of the conjunctiva and cornea. The eyelids become distorted and the eyelashes abrade the cornea. The cornea becomes vascularized and opaque and fibrovascular tissue extends into the cornea between the epithelium and Bowman's layer (pannus). Involved eyes are prone to secondary bacterial infections and eventually blindness ensues.